STATE OF CALIFORNIA 
 
 EARL WARREN, Governor 
 
 DEPARTMENT OF NATURAL RESOURCES 
 
 WARREN T. HANNUM. Director 
 
 DIVISION OF MINES 
 
 FERRY BUILDING. SAN FRANCISCO 11 
 OLAF P. JENKINS. Chief 
 
 SAN FRANCISCO SPECIAL REPORT 19 JUNE 1952 
 
 GEOLOGY AND CERAMIC 
 PROPERTIES 
 
 OF THE 
 
 lONE FORMATION, BUENA VISTA AREA 
 AMADOR COUNTY, CALIFORNIA 
 
 By JOSEPH A. PASK and MORT D. TURNER 
 
Digitized by the Internet Archive 
 
 in 2012 with funding from 
 
 University of California, Davis Libraries 
 
 http://archive.org/details/geologyceramicpr19pask 
 
GEOLOGY AND CERAMIC PROPERTIES OF THE lONE FORMATION, BUENA VISTA AREA, 
 
 AMADOR COUNTY, CALIFORNIA 
 
 By Joseph A. 1'ask * and Mort D. Turner »• 
 
 OUTLINE OF REPORT j,^^^ 
 
 Abstract ."> 
 
 Introduction 4 
 
 Sletliods of ill vest ignt ion 5 
 
 (leolojjy 5 
 
 Coraniic tests 
 
 Aniilication of different in I thermal analysis to clay mineralogy 7 
 
 Standnrd clay minerals 7 
 
 Variations in kaolinitc (jronp 10 
 
 Descriptive f;e<doKy 11 
 
 IJedrock series i;> 
 
 Annulor fironp V.i 
 
 Mariposa slate 14 
 
 Tertiary system 15 
 
 Mocene (V) jire-Iniip l)eds 15 
 
 E<.cene lone formation 16 
 
 Miocene (Vl Valley SjjriiiKs formation 20 
 
 Quaternary system 21 
 
 Terrace deposits 21 
 
 Recent alluvium 22 
 
 (ieologic history 22 
 
 Kconomic geoloRy 22 
 
 Clay 22 
 
 Other minerals 24 
 
 Value of ceramic test in geologic investigation 24 
 
 Selected bihlioKraphy 26 
 
 Appendix 27 
 
 Kexird of drill holes in Buena Vista area 27 
 
 Chemical analyses 38 
 
 Illustrations VaKC 
 
 I'late 1. (ieolo};ic map of r.ueiiM A'ista area . In pocket 
 
 2. Ceolo^ic structure sections A-K through Buena 
 
 Vista area In pocket 
 
 .'!. Ceolo^ic structure sections A-C through Buena 
 
 \'ista area In pocket 
 
 4. LoK of hole lS-1 showing' ceramic data In p(K'ket 
 
 Ki;;urel. Index map of central California showing location of 
 
 Buena Vista area 5 
 
 2. IHajirammatic representation of the crystal structure 
 
 of kaoliiiite G 
 
 :*>. Differential thermal analyses of standard clay min- 
 erals 7 
 
 4. Diagrammatic representation of the crystal structure 
 
 of illite 8 
 
 5. Diagrammatic representation of the crystal structure 
 
 of iiiontinorillonite !) 
 
 (>. Dia;,'ranimatic representation of the crystal structure 
 of montmorillonite 
 
 7. Differential thermal analyses of kaolinitic-type miner- 
 als from the Hneiia Vista area 10 
 
 8. Differential thermal analyses of kaolinite and non- 
 kaolinitic minerals from the Buena Vista area 11 
 
 1>. I'hoto of Buena Vista area 12 
 
 10. riiolo of greenstone ridge 13 
 
 11. I'hoto of greenstone ridge 14 
 
 12. I'hoto of Woolford clay pit 10 
 
 l.'{. I'hoto of KaiK-her clay i>it 17 
 
 14. I'hoto of Kaolin-Kye sand pit 1!> 
 
 I."). I'lioto of wax-exirai-tion plant 1J> 
 
 lO. I'hoto of Fancher clay iiit 1!) 
 
 • Associate I'rofessor of Ceramic Engineering, Division of Mineral 
 TerhiioloKy, College of Kngineering, I'niversity of California at 
 Ilerkcley. 
 '♦Assistant Mining Ceologist, California Division of Mines. Manu- 
 script submitted for publication November, 1951. 
 
 17. Photo of Chitwood clay pit 21 
 
 18. Photo of Chitwowl clay 21 
 
 19. Photo of Buena Vista Buttes 22 
 
 20. Photo of south side of Buena Vista Mesa 2."? 
 
 21. I'hoto of terrace gravel resting on Cheney Hill clay 2."> 
 
 22. I'hoto of channel cut into upi)er lone brown sandstone 2;» 
 
 2.">. I'hoto of old gold-placer workings in alluvium 24 
 
 24. Relation between differential thermal analyses, fired 
 
 color, and pyrometric cone equivalent 2~i 
 
 ABSTRACT 
 
 The Bneiia Vista area described in this report lies in the low 
 foothills of the Sierra Nevada in southeastern Amador County, 
 south of lone. It contains commercially important clay beds of the 
 lone formation. Eocene in age, which were deposited in a tropical 
 or semi-tropical climatic environment. 
 
 Surface ge(dogy was mapped and a study was made of the 
 ge<dogy and mineralogy of the clay from samjiles secured from 
 drill-h(de cores. Ceramic tests, consisting of differential thermal 
 analysis, pyrometric cone ecpiivalent determination, and tired color 
 of .samples containing clay were used as aids in this study. It was 
 found that the pyrometric cone equivalent (refractoriness) of a 
 clay could be estimated from a knowledge of the differential thermal 
 analysis and fired color of the clay. Because differential thermal 
 analysis and fired cidor may be obtained more quickly, easily, and 
 cheaply than ])yrom<'tric cone equivalent by standard procedure, 
 this method of determining approximate refractoriness will be of 
 great assistance to the geologist and miner looking for refractory 
 clay. 
 
 The clay minerals of the area were found to be members of the 
 kaolinite group, and by using ditTerential thermal analysis three 
 types and several subtypes of kaolinite group clay minerals were 
 identified. These types an<l subtypes were found to be useful and 
 valid aids in geologic correlation of members, and even lentils, of 
 the lone formation. 
 
 I'nderlying the Eocene sediments is the basement, or bedrock 
 series of the Sierra Nevada. The (ddest of these rocks exposed in 
 the jirea consists of meta-andesites and related greenstones of the 
 I'liper .Inrassic Amador gronji which are overlain by the I'pijer 
 .Jurassic Mariposa slate. One drill hole in the area reached the 
 Mariposa slate below the overlying Tertiary cover. The .Inrassic 
 rocks were f(dded and metamorphosed at the close of the .Turassic 
 jieriod. Clay an<l sand of an unnamed formation were found over- 
 lying the liasement rocks and underlying the lone formation in a 
 number of <lrill holes. The clay and sand may also be of Eocene 
 age, but their lithology does not indicate deposition in a tropical 
 environment, .\fter the i)re-Ione sedimentation the climate changed 
 to one which was more tropical and the surface rocks were deeply 
 weathered, l.aterite was formed on outcrops of greenstone and has 
 furnished some of the source material for the refractory clays in 
 the later lone sediments. 
 
 The i)re-Ione sediments are overlain unconformably by the lone 
 formation which, in the Buena \'ista area, is composed of two 
 members separated by an unconformity. 
 
 The lower member of the lone formation Cfuitains most of the 
 commercial clay of the area and is characterized by the rarity of 
 chlorite, biotite, and certain tyiK's of clays. It is divisible into three 
 lentils in the Buena Vista area. The lower lentil contains the 
 Edwin clay — which is mined near the town of lone — and reworked 
 laterite. The middle lentil contains the lignitic coal beds of the 
 area. The upper lentil contains the Cheney Hill clays and the white 
 lone sand. 
 
 The upper member of the lone formation is predominantly sandy 
 and contains two mappable units: a hard white sandstone at the 
 top of the member, and the Chitwood clay in the upper i)art of the 
 member. 
 
 The degree of alteration of minerals in the upper member of the 
 lone formation indicates that the climate was becoming more tem- 
 l)erate than during the deposition of the lower member. Temperate 
 climate continued into the later Tertiary eiH)clis ; the Valley 
 Springs and Mehrteu formations were formed in this climate. Meaii- 
 
 (3) 
 
Special Kepokt 10 
 
 while tli<> Sierra Ncviida liejiaii to riso csscTitially as a wfstwanl 
 tiltpd block. Tlip uplift iiRTcascd tho gradit'iit of the rivers which 
 hesaii to cut deep canyons rai)idly. 
 
 At the close of the time of deposition of the lone formation and 
 during the early Miocene there was a Iouk i>eriod of erosion, fol- 
 lowed by the deposition of volcanic ash represented by the rliyolitic 
 Valley Spriiifis formation. Khyolitic volcanism ^'ave way to ande- 
 sitic volcanism in the upper Miocene or I'liocene and the thick 
 mantle of andesite af;;,'lomerate of the Mehrten forTuation accumu- 
 lated over the entire area. Subsecpient erosion, accelerated by the 
 continued uptiltin;; of the Sierra Nevad.'i, removed all of the ande- 
 sitic material and much of the rhy(ditic ash from the lluena Vista 
 area. During' later st;i^'es of erosion, terr.nces were formed, mantle<l 
 with the dei)osits of auriferous jicravels derived {vom e.xhumed 
 Kocene travel channels which lay on the basement .surface con- 
 cealed by the Tertiary volcanic cover. 
 
 INTRODUCTION 
 
 Clays of the kaoliiiitic type are important raw materials 
 for a number of industries. In California such elays liave 
 been exploited to .some extent. It is desirable to add to 
 knowledjie of California elays, and to inve.stijiate the oeol- 
 o}iy of as many known clay areas as possible. 
 
 At the close of World War IT a series of 17 holes with a 
 total footajre of 4225 feet was drilled in Jackson Valley, 
 southwest of the villaoe of Buena Arista in southwest Ama- 
 dor County. The individual holes ranjied in depth from 
 63 feet to '395 feet and were from 680 feet to 2350 feet 
 apart horizontally. Summary loos and partial cores of 
 these holes were piven to the Division of Mines in 1948. 
 Because these cores represented a unifjue opportunity for 
 detailed study of the economically important lone forma- 
 tion, the Division of Mines and the Ceramic Eii<iineerino- 
 Laboratories of the I^niversity of California instituted a 
 joint study of the jreolofry and clays of the Buena Vista 
 area. 
 
 The loooiiio- of tlie cores ^ave a detailed lithologie col- 
 umn for each hole but this was not sufficient to allow corre- 
 lation of individual beds from hole to hole, except in a 
 few places. Mappino' of the surface jreolooy, experimenta- 
 tion with various methods of frraphic presentation, and 
 utilization of a number of ceramic technitiues were 
 necessary before a picture of the stratijiraphy could be 
 developed. The ceramic techniques, specifically differen- 
 tial thermal analysis, fired color, and pyrometric cone 
 ecjuivalent, are referred to as ceramic in the sense that 
 they are extensively used by ceramists and that they de- 
 pend upon the application of heat. Differential thermal 
 analysis is primarily of A-alue in aidino: in the determina- 
 tion of the mineraloorical composition. The fired color and 
 pyrometric cone ecpiivalent tests, in addition to providiiifj: 
 a ditferentiatino- factor, are also of economic importance 
 because they hclji to ascertain the potential value of a 
 clay to the ceramic industry. 
 
 The pur]>ose of the investiofation was to obtain informa- 
 tion about the detailed stratifiraphy of the Tertiary sedi- 
 ments of the area, the position of the already exploited 
 clay deposits in the stratijiraphic se(iuence, the location 
 and character of unexplored clay deposits, and the value 
 of ceramic testinji' technicjues as an aid in "iTolofi'lc investi- 
 gfations. 
 
 Altlioufrh the o-eoloojc study was the work of M. D. Tur- 
 ner and the ceramic study the work of Joseph A. Pask, the 
 interpretations and conclusions reached in each section 
 were the result of mutual effort. 
 
 Acli)}(>irlc(1(/mciils. The project was aided by research 
 orants from the Institute of Eno;ineerin<j: Research of the 
 Colleo-e of Enoineerino; of the University of California at 
 Berkeley, which paid part of the cost of lojyging the drill 
 cores and paid all of the cost of the ceramic testing. 
 
 The project was greatly aided by Val Freeman, who 
 assisted in logging the drill cores, plotted the results of the 
 logging, and fired the chip samples; by Maurice Warner, 
 who ran the differential thermal analyses; by Ralph 
 Adamo, who determined the pyrometric cone equivalents 
 and ran coh)r determinations on fired clay samples ; and by 
 Samuel R. Hoffman, who assisted with the plane table 
 mapping. 
 
 Jack Fancher and F. M. Ringer, ranchers of the Buena 
 Vista area, furnished valuable information concerning the 
 hi.story of clay producti(m in the area. T. C. Slater of the 
 Calaveras Cement Company, and Raymond Drew of the 
 American Lignite Products Company cooperated by pro- 
 viding the logs of holes which have been drilled in pros- 
 pecting for lignite, clay, and glass sand. 
 
 ficographi). The Buena Vista area is in the low foot- 
 hills of the Sierra Nevada between the Cosumnes and 
 Mokehnnne Rivers, about 4 miles south of lone and 10 
 miles west of Jackson, an area roughly rectangular in 
 shape and covering about 5 square miles. Elevations range 
 from 225 feet on Jackson Creek to 848 feet at the top of 
 Buena Vista Peak. 
 
 The Buena Vista area is a part of the Arroyo Seco dis- 
 sected pediment as described by Piper.^ The present topog- 
 raphy was formed during the Victor epoch. The entire j 
 area is drained by Jackson Creek which heads to the north- ' 
 east on the middle slopes of the Sierra Nevada and flows 
 past Buena Vista from east to west in a mile-wide flood 
 plain that bisects the area. Jackson Creek joins Dry Creek 
 a few miles west of Buena Vista. 
 
 In the north the hills are smoothly rounded and rise 
 more than 150 feet above Jackson Valley. Bare rock knobs 
 and cliffs are common only along the greenstone ridge. In 
 the south the lower hills are smooth and rounded like those 
 across Jackson Creek, but at a higher elevation rocky out- 
 crops and lines of low cliffs have been developed in the 
 Valley Springs formation. The most prominent topo- 
 graphic features are the Buena Vista Peaks, which are 
 capped by rhyolite cliffs nearly 100 feet high. 
 
 The climate of the Sierran foothills is Mediterranean, 
 with cool wet winters and hot dry summers. The average 
 annual precipitation is about 21 inches and falls almost 
 entirely as raiti from October to May. Snow is unusua^ 
 but freeziiig t<'niperatures are expected at night from 
 December to February. Summer temperatures of ovci 
 100° F. are common.- As a result of the seasonal rainfall 
 the streams are full and swift during the winter, whereas 
 in the summer they are completely dry. Jackson Creek 
 however, contains water through most of the year. 
 
 The flora also reflects the fluctuating water supply h\ 
 maturing in late spring. The hills are covered with trees 
 and shrubs, in places so thickly that passage is ver.A 
 difficult for a person on foot. The common shrubs ar( 
 
 • IMper, A. M., Gale, H. S., Thomas, If. E., and Robinson, T. W. 
 <:eo]ngv and pround-water hydrology of the Mokelumne area, Call- I 
 fornia : U. S. (ieol. Survey Water-Supply Paper 780, 230 pp., 1939^ I 
 
 -■ Sjirapue, Malcolm, Climate of California in Climate and Man : U. b J 
 Dept. Agr. Yearboolt 1941, pp. 793-795, 1941. 
 
loNE Formation, Buena Vista Area 
 
 123" 
 
 1220 
 
 I21« 
 
 1 i. yl L ^n Y 
 
 ', /^ < ©SACRAMENTO \ -^ . ^ 
 
 \ NAPA ;'^' '^ I ^, lAMADORr*^;: 
 
 -J I ^ I jSACRAMENTO 
 
 \ \ V ! ; 
 
 39° — 
 
 SON 
 
 M A V. 
 
 EL DORADO 
 
 1^ SANTA CLARA S 
 
 r" ' ^ O Son Jose *, 
 
 _<£l S^ 
 
 /STANISLAUS 
 
 Figure 1. Index map of central California showing location of Hnena Aista area. 
 
 chamisp {Adcnosfoma), manzanita (Arctostaphylos), 
 
 ;md poison oak (Rhus). The troos are various species of 
 
 oak {Quercux) with some scattered digger pines {Pinus 
 
 sahiniana Douglas). ]\Iost of the laud is pasture and 
 
 ranfje. The only cultivated areas are on the alluvium of 
 
 Jackson Valley, where wheat and other {grains are raised ; 
 
 water from wells is used for irrijiatiou. Tlie fauna is 
 
 typical of the Sierran foothills and consists of a large 
 
 ; variety of small herbiverous and carniverous animals. 
 
 ' History. After a long period of Indian occupancy, 
 
 ' the fir.st white people reached the area in 1848, and in 
 
 I that year farming and cattle fattening began in Jackson 
 
 ' Valley.'' Tn 1852, Tcodocio Yorba filed a Mexican grant 
 
 which was finally made to cover a large part of Jackson 
 
 Valley. "^ The resultant conflict in titles was not settled 
 
 until the 1860 's. During that time the rich alluvial valley 
 
 had become a gold-producing region itself, as well as an 
 
 important source of agricultural products for the ^Mother 
 
 Lode region. Coal and clay were later produced in large 
 
 quantities. The ranches and farms, however, have always 
 
 remained as the main source of wealth. 
 
 •Mason, J. D., Hi.storv of Amador t^ountv, California, p. 18!*, Oakland, 
 
 Thompson and West, 1881. 
 •Ibid, pp. 242-250. 
 
 METHODS OF INVESTIGATION 
 Geology 
 
 About 17 days were devoted to field study of the sur- 
 face geology by M. D. Turner during April 1950 and 
 January and April 1951. Outcrojw were plotted on U. S. 
 Forest Service aerial photographs on a scale of 1 :20,000 
 and on a V. S. Bureau of Reclamation topographic map. 
 Drawing No. C.I-598-D-2, at a scale of 1 :12,000 and a 
 contour interval of 10 feet. Several regions in the north- 
 east were unsurveyed on the original map. A small 
 portion of the unmapped area in the vicinity of the 
 Kaolin-Fye \)\\ was surveyed at the scale of the base map 
 with a plane table, alidade, and stadia rod. 
 
 "Work in the field stressed the identification of litho- 
 logic units of the Tertiary formations so that correlations 
 could be made with units differentiated in the drill cores. 
 Field identifications were supported by petrographic 
 study of 40 thin sections and a number of crushed 
 samples. The greatest aid in correlation was obtained 
 through interpretation of differential thermal analyses 
 of field samples and core samples. The cores, representing 
 1S42 feet of hole, or 43.(i percent of the total footage 
 drilled, were logged. Each identifiable unit was described 
 bv visual means as to color, texture, and mineral com- 
 
6 
 
 Special Report 10 
 
 position. Those data wore plotted at a scale of 1 inoli 
 equals 1 foot. Chip samples were taken for ceramic 
 testing. 
 
 Ceramic Tests 
 The ceramic tests employed during this work were 
 observation of fired color, pyromotric cone equivalent, 
 and differential thermal analysis. As geologists are gen- 
 erally not familiar with these tests, the following discus- 
 sion is presented. The many tests iisually made to 
 determine the degree of firing and the properties of 
 A'arious types of ceramic bodies or mixtures were not 
 included in the study. 
 
 Fired Color. Small pieces of core samples, about 1 inch 
 in diameter, were fired in an electric resistance-wire fur- 
 nace to a temperature of 1000° C. or 1832° F. These 
 retained their original shape because no fusion or disinte- 
 gration occurred. Some samples were also powdered to 
 pass a 70-mesh sieve prior to calcination. The fired colors 
 were unchanged, but the powdered form enabled the 
 measurement of percentage reflectance values relative to 
 magnesia as a standard. Measurements were obtained 
 with a Photovolt intrument. The data obtained with a 
 green filter were used for correlation as green light most 
 closely approaches the perceptibility of the human eye. 
 
 Clays, being hydrous aluminum silicates, should fire 
 white, but the presence of iron oxide or minerals con- 
 taining iron oxide will result in some shade of brown or 
 rod. This information is valuable, for the appearance of 
 iron oxide in unfired samples is often masked in some 
 manner, usually by carbonaceous material. The fired color 
 can thus be used as an aid to correlation where the pres- 
 ence of iron oxide is a characteristic. 
 
 Pyromciric Cone Equivalent. The pyromotric cone 
 equivalent values were obtained according to the specifi- 
 cations of A. S. T. M. Standard Test C24-46 ^ using a 
 Remmey oxy-acetylene furnace. Briefly, the method con- 
 sists of comparing the deformation rates of tetrahedral 
 cones, about 1 inch in height, made from the clays to be 
 tested, with standard cones. Series of numbered stand- 
 ard cones are available whose deformation temperatures 
 are known for given rates of heating. 
 
 In a system of oxides reacting according to the phase 
 rule without any, or a small amount of solid solution, 
 exposed to increasing temperatures, liquid will first ap- 
 pear at a eutoctic temperature, the amount of liquid being 
 dependent upon the composition. As the number of oxides 
 in the system is increased the temperature at which the 
 liquid appears is lowered because the new eutectic temp- 
 erature is lower. As the temperature is further increased, 
 the amount of liquid increases iintil the crystals disappear 
 entirely. Complete molting at one temperature occurs 
 only for compositions corresponding to true compounds 
 or to the eutectic composition. In aluminous silicate sys- 
 tems the licjuids formed have high viscosities, or low 
 fluidities, resulting in slow deformation instead of rapid 
 collapse of the cone. Thus, time becomes a factor, but 
 the heat-work for deformation remains the same. A given 
 cone will, therefore, deform at a higher temperature if 
 heated at a faster rate and at a lower temperature if 
 heated at a slower rate. This method of determining 
 "temperature" and refractoriness is of value and used 
 
 ^Manual of A. S. T. M. standard.s on refractory materials: Am. See. 
 Testing Materials, pp. 69-72, 1948. 
 
 extensively because it offers an opportunity to compare 
 a number of ceramic mixtures iinder similar physical 
 conditions. 
 
 Thjfcrcnfial TJierinal Analysis. Differential thermal 
 analysis determines the temperatures at which ondo- 
 thermic (lieat-absorbing) and exothermic (heat-evolving) 
 effects take place by measuring the temperature difference 
 between an unknown and a standard (alumina) during 
 a constant rate of increase of the furnace temperature. 
 For a given mineral those effects are the same and there- 
 fore constitute a means of identification. Endothermic 
 effects are caused by vaporization, decomposition, crystal 
 inversion, and fusion; exothermic, by oxidation (usually 
 of carbonaceous material) and crystallization. Other re- 
 search tools and tochni(iuos, however, are used to identify 
 the causes for the various heat effects if the information 
 is desired. 
 
 The experimental arrangement used to obtain the 
 curves was similar to those described in the literature." 
 The main dift'oronco was in the use of a recording potenti- 
 ometer with a range of — 0.25 to +0.25 millivolts which 
 allowed a visible record of the differential temperature 
 between the alumina and the unknown throughout an 
 analysis. The thermocouples wore platinum vs. platinum 
 — 10 percent rhodium. The heating rate was constant at 
 8.45 mv./hr., ecpiivalont to approximately an average of 
 13^° C. or 24° F. per minute. The amount of material 
 per test was approximately 1.8 grams. Changes in heating 
 rates cause slight shifts in peak temperatures because the 
 heat-work for a certain reaction remains constant. In 
 instances where reactions are dependent upon the addi- 
 tion of gases, such as oxidation, or dissipation of gases 
 or vapors, such as decomposition, the shifts are generally 
 greater because they also are dependent upon the ease 
 of movement of the gases or vapors through the sample 
 and the experimental set-up. Peaks are deviations in the 
 curve, both above and below the zero line. 
 
 •Spiel, Sidney, Berkelhamer, L. H., Pask, J. A., Davies, Ben, Differen- 
 tial thermal analysis — it.s application to clays and other aluminous 
 minerals : U. S. Bur. Mines Tech. Paper 664, 81 pp., 1945. 
 
 4 Si 
 
 s y 
 
 c = 72A 
 
 \l/ \l/ 
 o o 
 
 V ^ xy 6 
 
 
 6 
 
 6 (OH) 
 
 4 Al 
 
 i_ 
 
 ^MNr-'&gNr so 
 
 4 0*2 (OH) 
 
 4 Si 
 
 -b-Axis- 
 
 Kaolinite (OH) Al SiO,^ 
 a 4 4 10 
 
 
 FiGiKK 2. Diagrammatic ropresentalion of (lie crystal structure: 
 of l<aolinite. (After Gruncr.) 
 
loNE Formation, Buena Vista Area 
 
 APPLICATION OF DIFFERENTIAL THERMAL ANALYSIS 
 TO CLAY MINERALOGY 
 
 Clay minerals and quartz predominate in the sediments 
 in the Buena Vista area, although other minerals are 
 present in smaller amounts. The accurate determination 
 of the minerals was desirable both for geolofjic logging 
 and for economic importance. Once curves are obtained 
 for representative type-clay minerals, the differential 
 thermal analyzer enables identification of unknown clays. 
 The analyzer also easily detects minor variations that are 
 difficult to discern by regular petrographic or X-ray 
 methods. 
 
 Hj'drous minerals, such as clay, mica, talc, amphibole, 
 and the serpentine-chlorite series, show a characteristic 
 endothermic peak at characteristic temperatures due 
 to the evolution of (OH) — ions as water molecules. 
 Sometimes subsequent endothermic peaks due to further 
 breakdown and exothermic peaks due to crystallization 
 become additional identifying characteristics. Character- 
 istic endothermic effects are also obtained for carbonate- 
 containing minerals. 
 
 Carbonaceous material is usually oxidized at relatively 
 low temperatures and over a wide range of temperatures 
 and produces a broad exothermic peak. Anhydrous or 
 undecomposable minerals usually are not discernible un- 
 less they undergo an inversion, such as quartz does in 
 changing from the alpha to the beta crystalline form at 
 573° C. or 1063° F. with an absorption of heat. 
 
 Standard Clay Minerals 
 
 The clay minerals are divided into three main groups: ' 
 kaolinite, illite or hydratcd mica, and montmorillonite. 
 A number of minerals, such as attapulgite and beidellite, 
 do not fit into this classification and are included in a mis- 
 cellaneous grouping. Most clay minerals are essentially 
 hydrous aluminum silicates and are layerlike in crystal- 
 line structure. A brief description of the structures will 
 offer a greater appreciation of the differences between the 
 minerals. 
 
 The sizes of the silicon, aluminum, and oxygen ions 
 are such that a compact packing of oxygen and hydroxyl 
 
 anions around each of the cations forms (Si04) 
 
 and (AlOo) or (Al(OH)o) groups. 
 
 The superscript refers to the valence charge remaining 
 because of more negative valences from four or six ~~ 
 or six (Oil ) - than can be .sati.sfied by Si * * * * or Al * * \ 
 These groupings persist although there are several in- 
 stances of structure where aluminum substitutes for 
 silicon and has only four oxygen neighbors forming Uw 
 ( AlOj ) group. 
 
 The (Si04) groups assemble to form a continuous 
 
 structure in two directions resulting in a silica sheet. Look- 
 ing at the edge of the sheet all of the oxygen valences on 
 one side have been satisfied Avhereas on the other side 
 unsatisfied oxygens exist that still have one negative 
 valence or charge. Looking down on the sheet the 
 oxygens are arranged in a hexagonal network. The 
 (Al (),j) groups likewise are packed to form 
 
 'Brindley, O. AV. (editor), X-ray idontification and cry.>?tal struc- 
 tures of clay minerals: Tlie Mineralogical Society (Clay Minerals 
 Croup), :H', pp., Lon<lon, 1!)51. 
 Grim, K. 10., Modern concepts of clay materials: Jour. Geology, vol. 
 
 50, pp. 22.5-275, 1942. 
 Marshall, C. E., The colloid chemistry of the silicate minerals, p. 14, 
 Academic I'ress, 1949. 
 
 500°C IOOO°C. 
 
 FiGiKE ;?. Differential thermal analyses of standard clay minerals. 
 
8 
 
 Special Report 10 
 
 a continnons assombla<i'o in two directions rosultinjj in a 
 strnctnre similar to a fjibbsite sheet. Lookin<i' at its edpe 
 the oxygen valences on both sides have not been satisfied 
 because of an insufficient number of positive charges from 
 the Al ■^ ■" ■". Thus, a step toward valence balance is taken 
 with each substitution of an (Oil)- ion for an -- ion. 
 
 Complete substitution results in (A^OIDc) p:roups. 
 
 A compact assembla<>e of these p;ronps so that each (OH)- 
 ion is shared between two Al + * * ions forms the mineral 
 •i'ibbsite. 
 
 Tlie sheets may assemble in several combinations with 
 isomorphous substitutions of Al * * * for Si ^ * * "■, and also 
 Mfr-^% Fq*% and Fe*** for Al-^"+ to form the several 
 groups of clay minerals. 
 
 Kaolinite Group. The recognized minerals of this 
 group are : kaolinite, dickite, nacrite, halloysite — hy- 
 drated halloy.site, and anauxite. They are referred to as 
 the 1 : 1 lattice type for they are made up of layers con- 
 taining one silica and one gibbsite sheet. The sheets are 
 joined by sharing oxygens wherever necessary to satisfy 
 valence charges. Layers are held together by van der 
 "Waals forces, which are not direct valence bonds. These 
 forces are weak and are responsible for the dominant 
 platy character of the crystals. As can be determined from 
 the schematic sketch of the kaolinite molecule (figure 2) 
 the formula is Ah.0.r2Si(), -211,0 or, structurally, (OH) 4 
 Ah.(Si20.-,). It is probable that very little or no isomor- 
 phous substitution occurs. 
 
 c = IO.OA 
 
 ^9V%R^ 
 
 yk 
 
 6 
 
 4- y Si yAl 
 
 A Q ^ A 9 ^ 2(0H).4 
 
 
 / 
 
 
 ■s \ / \ \ / 
 
 o o 
 
 'a (^ ^ w 
 
 ^t-o-^m-xf 
 
 2(0H)-i-4 
 
 4-y Si yAl 
 6 
 
 yk 
 
 ■ b- Axis- 
 
 Ill He (OH)^Ky(AI^ Fe^ Mg^ Mg^) (Sig_y Aly ) 0^^ 
 
 Figure 4. DiagramnLitic representation of the crystal structure 
 of illite. (After Grim, 1942.) 
 
 A differential thermal analysis of a typical kaolinite 
 is shown in figure 3. The endothermic peak at approxi- 
 mately 600° C. or 1112° F. results from driving off water 
 from the structure. Two theories exist for the appearance 
 of the sharp exothermic peak at 980° C. or 1796° F. One 
 states that it is due to the crystallization of gamma-alu- 
 mina and the other, to the microcrystallization of mullite 
 (SALO.i-SSiO,). Nevertheless, this peak, with the endo- 
 thermic one, are identifying characteristics of kaolinite. 
 
 Dickite and nacrite are similar to kaolinite in all re- 
 spects except in the degree of orientation of the layers 
 over one another.*^ The curve for dickite (figure 3) has 
 its endothermic peak at a higher temperature than 
 kaolinite ; and nacrite,^ for which a curve is not avail- 
 able, presumably would show a still higher endothermic 
 peak because of the less random packing of layers. 
 
 llallovsite has the formula A1..0:r2SiOo-2HoO and 
 liydrated halloysite Al2O.r2SiO2-4H2O.10 The latter is 
 formed by the addition of oriented layers of water be- 
 tween the kaolinite layers. A series exists between the two 
 forms. The chief differentiating characteristics of the hal- 
 loysite differential thermal curve (figure 3) are the ap- 
 pearance of a large endothermic peak at approximately 
 150° C. or 302° F. due to the vaporization of the inter- 
 layer water (the size of the peak depends upon the amount 
 of inter-layer water) and a sharp return to the neutral 
 temperature after the main endothermic peak at 600° 
 C, in contrast with a symmetrical endothermic peak as 
 exhibited by kaolinite. The particles of halloysite are rod- 
 shaped, formed by the curling of thin plates. 
 
 Anauxite is formed by the addition of oriented silica 
 layers between the kaolinite layers — the formula being 
 Al2O3-3SiO2-2H2O.11 A series can thus exist between 
 kaolinite and anauxite. The nature of the differential 
 thermal analysis is, as yet, not certain. Several analyses 
 of samples considered to be anauxite produced curves 
 similar to those for kaolinite but with smaller heat effects. 
 Work is in progress to settle this point. 
 
 IllHc or Hydratcd Mica Group. Sufficient work has 
 not been done on this group to classify its members under 
 specific mineral names. It is referred to as the 2 :1 lattice 
 type, for it is made up of layers containing a gibbsite sheet 
 sandwiched between silica sheets. These are joined by the 
 sharing of oxygens between alumina and silica sheets 
 wherever necessary to satisfy valence charges leaving only 
 a few excess charges at the sheet interfaces that have to 
 be satisfied with (Oil)- ions. The schematic sketch (figure 
 4) shows this arrangement. 
 
 It is essential for the constitution of this group to have 
 isomorphous substitutions of Al * '^ * for Si ^ '^ * * in the 
 silica sheets. The resv;ltant loss of the positive charge, and 
 thus unbalance, is made up by the introduction of K* 
 ions between the layers. In addition, isomorphous sub-, 
 stitutions of Mg **, Fe * *, and Fe + * ■" can easily occur for 
 Al "^ "^ * in the gibbsite sheet. A series of illites is formed 
 
 * Hendrick.s, S. B., On the crystal structure of the clay minerals: dick- 
 ite, halloysite and hydrated halloysite : Jour. Mineralog. See. 
 America, vol. 23, pp. 295-301, 1938. 
 
 " Hendricl<s, S. B., The crystal structure of nacrite Al20s-2Si02-2H:0 
 and the polymorphism of the kaolin minerals : Zeitschr. Krystal- 
 lographie, band 100, pp. 509-518, 1939. 
 
 >" Hendricks, S. B., Crystal structure of clay minerals, op. cit. 
 
 11 Hendricks, S. B., Concerning the crystal structure of kaolinite 
 Al203-2Si02-2H20 and the composition of anauxite: Zeitschr. 
 Krystallographie, band 95. p. 247, 1936. 
 
Tone Formation, Buena Vista Area 
 
 r 
 
 9.6-214 /i + 
 
 c-Axis 
 
 n HgO 
 
 ^^^^^^^^^^ 
 
 A Q ^ A Q 
 
 6 
 4 Si 
 
 2 (0H)+4 
 
 o o 
 
 /IN 
 
 nI/ 
 
 o 
 
 ^1^ 
 
 
 4^' 
 /i\ 
 
 4 Al 
 
 2 (0H)+ 4 
 
 -WN^^^^ To' 
 
 • b- Axis 
 
 Montmorillonite (OHl^ Al^ SigO^Q n H^O 
 
 Figure 5. Diagrammatic represpiitation of tlip crystal structure 
 of montmorillonite. (After Hoffman, Endcll, and Wilm.) 
 
 as Al*** is substituted for Si * * * * up to a maximum of 
 15 percent of the silicon ions. If 25 percent of the posi- 
 tions are replaced, mica results, showing the close rehi- 
 tionship of the group to mica. The resultant formulae 
 become : 
 
 Illite— K2O • 5A1..():, • 14SiO.> • 4H2O or 
 
 (On)4K,(Al4,Fe4,Mnr,,) (Sis-,-Al,) O,,,. 
 Mica— KoO • 3A1.,0., • 6SiO.. • 2II..0 or 
 
 (OH)4K,(Al4,Pe4,Mgo) (Sio-Al,) O,,,. 
 
 Differential thermal analyses of illites (figure 3) show 
 the presence of three peaks: two similar to those for 
 kaolinite but smaller and less sharp, and another small 
 endothermic peak at about 800° C. or 1472° F. The 
 smaller, broader peaks are due to a comparatively slow 
 rate of breakdown of the structure. 
 
 Montmorillonite Group. This group is also referred 
 to as the 2 :1 lattice type consisting of a gibbsite sheet 
 sandwiched between silica sheets.'- The isomorphous sub- 
 stitutions recognized in montmorillonites are Mg * *, Fe * *, 
 and Fe * * * for Al * * * in the gibbsite sheets. The generally 
 accepted structure suggested by Hoffman, Endell, and 
 Wilm ^^ is shown in figure 5; figure 6 pictures tlie .struc- 
 ture propo.sed by Edelman and Favejee,'^ which is favored 
 by some workers. 
 
 "Hoffman, IT., Knflell, K., and Wilm, D., Crystal structure and swell- 
 ing of montmorillonite: Zeitsclir. Kristallograpliie, band 86, pp. 
 .•i40-.'i48, 193:!. 
 
 "Edelman, C. H. and Favejee, ,1. Ch. I>., On the crystal structure of 
 montmorillonite and halloysite : Zeitschr. Kristallographie, band 
 102, pp. 417-431, 1940. 
 
 n HgO 
 
 C = ^I40A 
 
 A % 
 
 A 
 
 six \l/ 
 
 o o 
 
 /|\ /|N 
 
 / . \ / I \ 
 
 6 
 
 \l/ si /- 
 
 O O 
 
 / I N/ I \ 
 
 6 
 
 JL_ 
 
 b-Axis 
 
 2(0H) 
 
 2 Si 
 
 6 
 2 Si 
 
 g^Sao^Nx eo 
 
 4 (0H)+2 
 
 4 Al 
 
 4 (0H)+ 2 
 
 2 Si 
 
 2 Si 
 
 2(0H) 
 
 Montmorillonite (OHJi^AI^ ^'e^i6 " ^2^ 
 
 Fkhkk (i. Diagrammatic rcprcscnlalioii of tlio crystal structure 
 of niontmorillonitc. (After Eddnian and Favejee.) 
 
 Tlie group can be- represented by a composition tri- 
 angle with apexes of the oxides of the middle sheet ( AI2O3, 
 J\IgO,Fe20.i). The pure end members tlien are: 
 Pvrophvllite — - 
 
 ■Al,0;',-4Si(),-II,Oor (OIDjAUCSi.Or.), 
 Talc — Saponite — 
 
 3MgO-4SiO.-ir,Oor ( OH )4Mgc (81305)4 
 Nontronite — 
 
 Fe,.Oa-4.Si02-n.O or (OH)4Fe4(Si20.-,)4 
 
 The end members themselves do not exhibit such prop- 
 erties as high base exchange, plasticity, and expanding 
 lattice, that are cliaracteristics of this group. The typical 
 montmoriUonitic clays, such as beutonite, occur within 
 this composition triangle close to the AI2O3 apex and the 
 
10 
 
 Ri'EciAL Report 10 
 
 Al.O.rMpO side. The expandinp: lattice is associated with 
 the presence of additional water between the layers which 
 is driven off completely at dryinp: temperatures of about 
 200° C. or 392° F. The structural formula for the typical 
 montmorillonite becomes: (OH)4(Al4,FeG,Mg:o) (SioO.-,)4' 
 nlloO. 
 
 The differential thermal analysis shown (fijrure 3) is 
 representative of a typical montmorillonite. The reac- 
 tions <i:enerally occur more rapidly than in the illite *iroup, 
 resulting: in three sharper, more distinct peaks, and the 
 first endothermic peak is at a hip'her temperature (about 
 700° C. or 1292° F.). Chan<i-es in relative size and slight 
 shifts in position of all three peaks occur with chanp:cs in 
 composition, but the exact pattern is not known. 
 
 Miscellaneous Clay Minerals. Attapulpite and beidel- 
 lite are the best known of the clay minerals that do not 
 fall into one of the three main "roups. The structure of 
 attapulgite, as worked out by Bradley, ^^ is similar to the 
 2 :1 lattice type except that the silica sheets are arranjjcd 
 so that the silicon ions occur in strips alternately on either 
 side of the oxygens, and the gibbsite sheet occurs in cor- 
 responding strips, prodiTcing a fibrous structure. Sub- 
 stitutions of Mg * * for Al * + * occur extensively, the mag- 
 nesium end member being (OII)2lMg.-.Si,sOi>()-8Il20. 
 
 Beidellite is often included in the montmorillonite 
 group because of its close similarity. However, as it does 
 not exactly follow the structural pattern of the montmoril- 
 lonites, it should be listed separately. 
 
 Marshall ^^ suggests that the mineral is formed by sub- 
 stitutions of Al * + * for Si * + * * in the silica sheets of the 
 montmorillonite structure. The extra charges are, how- 
 ever, not balanced by introduction of K * ions between the 
 layers as in illite but by introduction of additional posi- 
 tive charges in the gibbsite sheet by simply adding Mg * * 
 ions or replacing an Al "■ * * ion by two Mg * * ions. This is 
 possible because not all of the available cation positions in 
 the gibbsite sheet are filled. 
 
 Pask ^^ suggests that the mineral is formed by an inter- 
 layer mixing of the montmorillonite and kaolinite-type 
 layers. Such a structure pattern can account for all beidel- 
 lites giving a series or partial series between kaolinite 
 and montmorillonite. 
 
 Variations in Kaolinite Group 
 
 The classifications of the main clay groups, as outlined, 
 are based on representative specimens from type areas. 
 During the present studies it became apparent that less 
 of the type mineral kaolinite was present than other mem- 
 bers of the kaolinite group. Practically all the Buena Vista 
 area clays examined with the differential thermal ana- 
 lyzer, however, gave kaolinitic-type curves — an endo- 
 thermic peak at about 500-600° C. or 932-1112° F. and an 
 exothermic peak at about 880-980° C. or 1616-1796° F.— 
 with variations in intensity and shape of the peaks, par- 
 ticularly of the exothermic. Future mineralogical studies 
 will probably .show that the variations are due to intcrlayer 
 mixtures. 
 
 " Bradley, W. F., The .structural scheme of attapulgite : Am. Mineral- 
 ogist, vol. 2S, p. 1, 1943. 
 
 ^''Marshall, C. E., Soil .science and mineralogy: Soil Sci. Soc. America 
 Jour., vol. 1, pp. 23-31, 1937. 
 
 '"Pask, J. A. and Davies, Ben, Thermal analysis of clay minerals and 
 acid extraction of alumina from clays : U. S. Bur. Mines llept. 
 Inv. 3737, 28 pp., 1943. 
 
 Type I 
 
 Type lo 
 
 Type I 
 
 Type Ho ;:= 
 
 Type HI 
 
 Type Ho 
 
 Type nib 
 
 500°C IOOO°C 
 
 KiGi'KE 7. Differential thermal analy.ses of kaolinitic-type minerals 
 from the Buena Vi.sta area. 
 
loNE Formation, Buena Vista Area 
 
 11 
 
 Type I 
 
 Type Ir 
 
 Type Ir 
 
 Type Ir 
 
 Type In 
 
 Type Ih 
 
 montmofillonife 
 
 Because classification desirable for purposes of the 
 study was based on the shape of the peaks of the differen- 
 tial thermal curves, the following types Avere differen- 
 tiated (fig. 7) : 
 Type I. Typical kaolinite. A sliarp and narrow exothermic peak 
 
 equal to, or greater in size than, the endothermic. 
 Type la. Between I and II. 
 Type II. A sharp and narrow exothermic peak one-half or less in 
 
 size than the endothermic. 
 Type I la. Between II and III. 
 
 Type III. Exothermic peak small, l)roa(l, and rounded; endo- 
 thermic peak smaller tlian that for I and II. 
 Type Ilia. Exothermic peak very small or non-existent. 
 Type Illh. Similar to III ; exothermic peak larger in area, and more 
 rounded; both peaks at a slightly lower temperature. 
 
 A sub-type of any of these, identified by the letter " h " 
 (as: Type Th), has a tendency toward a halloysite-type 
 endothermic peak. A sub-type identified by the letter "r" 
 (as: Type Ir) has the heights of the peaks reduced by 
 presence of quartz or other relatively inert minerals. 
 Types I, II, and III were differentiated early in the work 
 but many samples were found that had intermediate char- 
 acteristics that were responsible for establishment of 
 Types la. Ila, Ilia, and 111b. There are still some samples 
 that are obviously intermediate in structure and are listed, 
 for in.stance, as I (tending toward la). Indications thus 
 exist of a continuous series between Types I, and II, and 
 II and III. 
 
 As indicated, dilution of the quantity of clay mineral 
 by cpiart/ and other relatively inert minerals causes only 
 a diminution of both peaks. Figure 8 shows a selection of 
 Type 1 curves with decreasing peak sizes. The presence of 
 quartz was determined when desired by rerunning the 
 curve after the sample cooled below the P — a (piartz inver- 
 sion temperature of 573° C. or 1063° F. This procedure is 
 necessary because the quartz peak is normally masked by 
 the endothermic peak of the kaolinitic clay minerals, which 
 is not reversible. 
 
 Carbonaceous material in small amounts does not affect 
 the clay mineral peaks but causes the superposition of a 
 broad exothermic peak due to oxidation of the organic ma- 
 terial. The size and position of the peak varies with the 
 amount and nature of the carbonaceous nuiterial. 
 
 Several additional types of curves were encountered as 
 shown in figure 8. The minerals responsible for the differ- 
 ences have not been identified definitely and the curves 
 were u.sed onlj- for geologic correlation. 
 
 DESCRIPTIVE GEOLOGY 
 
 Earlier Work. Because the Buena Vista area was an 
 early source of minerals, it has been studied by several 
 geologists. Mason '" gave a general geological account, in- 
 cluding a .stratigraphic section of Buena Vista Peak. The 
 monumental geological survey of the Sierra Nevada, pub- 
 lished in the folio series of the IT. S. Geological Survey, 
 contained the first modern geologic stiuly of the area. The 
 Buena Vista area was included in the Jackson quadrangle 
 mapped by Turner.'** He considered the rhyolitic clay rock 
 to be in the lone formation. Liiulgren '" shoAved that the 
 
 Figure 8. DifTerentlal theniiMl analyses of kaolinite having in- 
 creasing: (luartz content, and diflfcreiiti.-il tiierni.-il analy.ses of non- 
 kaolinitic minerals from the Buena Vista area. 
 
 " Mason. J. D., op. cit., pp. 1 25-1 Sfi. 
 
 "Turner, H. W., U. S. Geol. Survey Gcol. Atlas, Jackson folio (no. 
 
 11), 1S94. 
 '» LindKren, Waldemar, The Tertiarv gravels of the Sierra Nevada of 
 
 California: U. S. Geol. Survey Prof. Paper 73, pp. 21-28, 196-197, 
 
 1911. 
 
12 
 
 Si'EClAL HePOKT id 
 
 Fi(;iRE 
 
 I'uoiui A'ista area frmii the top of Bueiia A'ista I'eak. Jackson A'alley in center. Camera facing north-northwest. 
 
 early Tertiary rivers were the source of the sediments de- 
 posited in lone time and delineated their courses. Dicker- 
 son,-" Clark, -^ and Clark and Yokes -- determined the a^e 
 of the lone formation during studies of the Eocene of Cali- 
 fornia. 
 
 An overall study of the Tone formation was made by 
 Allen -^ who paid particular attention to the Amador 
 County area. The lone formation was restricted to exclude 
 all of the rhyolitic sediments, which had previously been 
 included as the upper part of the lone, and to include 
 sediments of a specific litholoj.nc character. Stearnes ^* 
 published a freolojric map coverino' the Buena Vista area 
 that was essentially adapted from the Jackson folio. -•'• 
 Piper -''' remapped the entire lone area on a lar(>er scale, 
 usiufi' the restricted lone, set up by Allen, and introduced 
 the Valley Springs and Mehrten formations. The bed- 
 rock series, since it was mapped in the 1890 's, received 
 little attention until Taliaferro defined the Amador group 
 and its component formations.-" 
 
 Bates -"* made a detailed study of the commercial clays 
 
 20 Dickerson, R. E., Fauna of the P^ocene at Marysville Buttes, Cali- 
 fornia : California Univ. Dept. Geol. Sci., Bull., vol. 7, pp. 257-298, 
 
 1913. 
 Dickerson, R. K., Stratigraphy and fauna of the Tejon Eocene of 
 
 California : California Univ., Dept. Geol. Sci., Bull., vol. 9, pp. 
 
 387-417, 1916. 
 =1 Clark, B. L., The .stratigraphy and faunal relationships of the Mega- 
 
 noK group middle Eocene of California: Jour. Geology, vol. 29, 
 
 pp. 161-165, 1921. 
 — Clark, B. L., and Voke.s, H. E., Summary of the marine Eocene 
 
 sequence of western North America : Geol. Soc. America Bull. vol. 
 
 47, pp. 851-878, 1936. 
 ^-'i Allen, V. T., The lone formation of California: California Univ., 
 
 Dept. Geol. Sci., Bull., vol. IS, pp. 347-448, 1929. 
 2* Stearnes, H. T., Robinson, T. AV., and Taylor, G. H., Geology and 
 
 water resources of the Mokehimne area, California : U. S. Geol. 
 
 Survey Water-Supply Paper 619, 402 i)p., 1930. 
 25 Turner, H. W., op. cit. 
 2» Piper, A. M., op. cit. 
 2" Taliaferro, N. L., Manganese d(>posits of the Sierra Nevada, their 
 
 genesis and metamorphism : California Div. Mines Bull. 125, pp. 
 
 280-286, 306-307, 1943. 
 =» Bales, T. F., Origin of the Edwin clay, lone, California : Geol. Soc. 
 
 America Bull., vol. 56, pp. 1-38, 1943. 
 
 of the Tone area, including some of the clays discussed in 
 this paper. 
 
 General Geology. The oldest rocks in the area, the 
 bedrock series, consist of the Upper Jurassic Amador 
 group and Mariposa slates. They are folded metamorphic 
 rocks that are more resistant to erosion than the later 
 sediments of the area. 
 
 No Cretaceous rocks crop out in the area, although they 
 have been encountered during drilling of wells in the 
 Great Valley and at the surface at Folsom, 27 miles north. 
 
 Lying on the bedrock in the Buena Vista Basin are 
 gray and green shale and sand of probable Eocene age. 
 They are nowhere exposed at the surface but were pene- 
 trated in several of the drill holes. The Tone formation, 
 probably of Eocene age, overlies these earlier Eocene ( ?) 
 sediments, and is divided into the lower lone and upper 
 lone members. The lower Tone clay and sand beds are 
 exposed throughout most of the area north of Jackson 
 Valley ; the best expo.sures of upper Tone are on the lower 
 slopes of Buena Vista I'eak. The Valley Springs forma- 
 tion, possibly of Miocene age, was laid down on the 
 eroded surface of the Tone formation and is characterized 
 by unmetamorphosed rhyolitic debris. Tt forms the highest 
 part of Buena Vista T'eak and covers the region to the 
 west of the bedrock ridge. No evidence of the Mehrten 
 formation was found in the T>uena Vista area although it 
 rests on the ^'alley Springs formation in surrounding 
 regions. 
 
 Quaternary terrace gravel and sand from various 
 sources Avere deposited throughout the area, covering the 
 tops of many of the higher hills. Jackson Valley, and all 
 of the small valleys that drain into it, are blanketed with 
 Keceiit alluvium. The jiradients of most of the streams 
 are low and the alluvium reaches the heads of the valleys 
 in many places. 
 
loNK FOK.M 
 'J'iihlc I. Siniimni!/ of 
 
 \'riON, IJl'KNA A'iSTA AUVX 
 
 rock fornintioiix in the liiicnii yiisin urcii. 
 
 r.\ 
 
 Age 
 
 Grouj) and formation 
 
 Thickness 
 in feet 
 
 Cieneral character 
 
 >< 
 
 < 
 
 K 
 (6 
 (a) 
 H 
 
 < 
 
 C 
 
 Recent 
 
 Pleistocene 
 
 Miocene (7) 
 
 Middle (7) Eocene 
 
 Eocene (7) 
 
 Upper Jurassic 
 
 Alluvium (Qal) 
 
 -Unconformity- 
 
 Terrace Gravels (Qt) 
 
 -Unconformity- 
 
 Valley Springs formation (Tvs) 
 
 Unconformity- 
 Upper lone member 
 Unconformity 
 
 Lower 
 lone 
 
 momhcr 
 
 Unconformity- 
 
 Upper 
 lentil 
 
 Middle 
 lentil 
 
 Lower 
 lentil 
 
 Unnamed prc-Ione beds 
 
 -Unconformity- 
 
 Mariposa formation (.Im) 
 
 0- 
 50 ± 
 
 Silt, sand, and gravel in present stream beds and beneath flood plains. Includes 
 alluvial fan material. 
 
 0- 
 18 
 
 Auriferous sand, gravel, and water-worn cobbles on remnants of stream ter- 
 races at elevations of from 250 feet to 400 feet. 
 
 0- 
 458 
 
 Rhyolitc tuff, weathered rhyolite tuff ("clay rock"), and rhyolite-bearing 
 sands and conglomerates. 
 
 0- 
 225 = 
 
 White to brown sands and sandy clays. White to gray hard sandstone at top 
 of member. Includes the Chitwood clay. 
 
 0- 
 415 = 
 
 White, gray, tan, brown, and red clay, lignite, clayey sands, and reworked 
 
 laterite. 
 Upper lefitil includes the lone sand and Cheney Hill clay. 
 Middle lentil includes three lignite beds. 
 Lower lentil includes F^dwin clay. 
 
 0- 
 131-1- 
 
 Gray, green, Bn<l greenish white sands and clays (not exposed at surface). 
 
 BiifT to pink clay derived by weathering from black slate (not exposed at 
 surface). 
 
 .Amador 
 (jrou|) 
 
 Logtown Ridge 
 formation (Jlr) 
 
 Greenstone (augite ande.site flows and agglomerates with associated intru- 
 sivcs), weathered to laterite in many places. 
 
 Tlio Tertiary foniuitioiis liavo not botMi folded or faulted 
 since deposition, but the whole area wa.s tilted toward 
 the southwest as a unit durin<j: the Tertiary and Quater- 
 nary periods when the Sierra Nevada was bein-r elevated.-'' 
 The Tertiary sediments, however, were depcwited with 
 initial dips. The lower lone member, which was laid down 
 in a wide shallow valley, the Hnena Vista Basin, con- 
 formed to the slope of the sides of the basin and has since 
 been little disturbed. The lon^' axis of the valley seems 
 to be parallel to the strike of the iiiKlerlyin«; bedrock, 
 about X. 30° W., and a rid^'e of jrreenstone mav be traced 
 
 "" Lindgren, op. cit., iip. 4(')-4S. 
 Matthcs. K. V... CcDloKic history of the Ycsemite \';illev ; V. .S. Geol. 
 Survey Prof. Paper ICO, pp. ■l.'i-44, HtSO. 
 
 l-'Kil liK 10. (IiTi'iisloiic i-|(U'i' south uf .liicUsoii \ alli'v. < Ii-eeiistciiic 
 
 croiipiii}; out as roiiiidcd boulders in ;;i'ass.v meadow. Uneiui X'ista 
 
 I'eaUs in lia(k;;iduiiil. Ciinera beaiin^ east-southeast. 
 
 al(»iio- the west side of the basin and for many miles north 
 and .south. \\y upper lone time the basin was essentially 
 full and the sediments and volcanic rocks have a general 
 dip away from tlie crest of the Sierra Nevada. 
 
 Bedrock Series 
 The bedrock formations in the area are the Upper 
 Jurassic Logtown Ridge and associated feldsjiar por- 
 phyry intrusivcs of the Amador grouji, commonly called 
 greenstone, and the l'p])cr .Turassic Marijjosa slate. 
 
 Amador Group 
 
 Amador mctavolcanic rocks and Mariposa slate under- 
 lie the entire area, but only the Amador group has been 
 exposed by erosion. (Jreenstone crojis out as rough, rocky 
 hills ill the extreme northwest corner of the mapped area 
 and in a small area a third of a mile southwest of the 
 Chitwood pit. Several of the drill-holes reached green- 
 stone, as indicated on the cross-sections. Taliaferro-'" 
 found that the Logtown Kidge formation 'svas originally 
 com|)os(>d of augite andesite tuffs, agglomerates, and 
 flows that have since been metamorphosed to amphibolite 
 and chlorite schists.- 
 
 Three ditferential thermal analyses were run on the 
 greenstone; two were weathered samples from the bot- 
 toms of holes 7-1 and 24-4, and the third was an nnweath- 
 cred surface samiile collected on the greenstone ridge just 
 outside the boundaries of the area. Each of the curves was 
 very irregular but showed jieaks characteristic of chlorite. 
 Onlv in the liiiihlx' weathered gi-eenst(»ne from hole 7-1 
 
 ' Taliafen-o. .\". 1,., r.]). cit., pp. 2s:;-2S 1. 
 
]4 
 
 Si'KciAr. HLroKT If) 
 
 I'kukk 11. South i'ikI of main jji-eeiistonc oiiU'i-op area north 
 of Jackson Valley. Camera hearing east-northeast. 
 
 Avoro tlioro iiicipi(>iit peaks of tlic type eliaracteristic of 
 kaolinite. 
 
 In adjaeent areas wliere the base of tlio Loofown Ridjje 
 fonnation is exposed, it rests on the Cosumnes formation 
 of the Amador g-ronp. The Amador group rests with pro- 
 found angular unconformity on the highly metamor- 
 phosed Calaveras rocks of Paleozoic age. There is no 
 direct evidence that the Cosumnes formation and Paleo- 
 zoic rocks underlie the Buena Vista area but it is 
 probable that they do. T Upward, the Amador group grades 
 into the I\Iari])osa slates. 
 
 Taliaferro -'^ says that "the exact age of the Amador is 
 not known, but it is believed to extend from the upper 
 Middle to the lovi.or Upper Jurassic. . . . the best avail- 
 able evidence indicates that the Mariposa is Oxfordian 
 and, possibly, lower Kimmeridgian." 
 
 Climate, rate of erosion, or both, changed at the be- 
 ginning of lone time in such a way that intense tropical 
 weathering caused the formation of laterite on exposed 
 stable greenstone surfaces. Krumbein and Sloss ^'- de- 
 scribed the process of laterization as "the normal, soil 
 forming process in the tropics. It concentrates iron or 
 aluminum oxides, or both, in the B-horizon (zone of 
 reprecipitation below leached zone), at the expense of 
 the silica, which is leached out. Chemical weathering is 
 rapid. Kaolinitic clay minerals are normal end products 
 in some circumstances but, in others, the clay minerals 
 are not stable. AVhere clay breakdown occurs, silica is 
 removed, and the ahnniniim remains behind as a hydrate. 
 Soil formed by the process is laterite." 
 
 The weathering of the laterite is not known to have 
 progressed to the point of producing bauxitic material 
 anywhere in the Buena Vista area nor was highly piso- 
 litic laterite, such as that found near Jones Butte, ^^ 
 found in the area. Most of the laterite on the surface and 
 in the drill-hole cores is mottled smooth clay which is not 
 especially plastic. It is colored from nearly solid red to 
 combinations of red, yellow, purpl<^, gray, buff, and 
 Avhite. 
 
 The only outcrops of laterite are along the sides and on 
 top of the greenstone ridge, both north and south of 
 Jackson Creek. It is well exposed south of the Woolford 
 pit and arouiul hole 24-."), Avhere 63 feet of lateritic 
 
 =» Taliaffrro, N. !>., op. rit., p. 2S4. 
 
 ■'-Krumbein, W. ('., and Slosss, L. L., Stratigraphy and sedimentation, 
 
 pp. l.'iO-lol, San Francisco, W. H. Freeman and Company, 1951. 
 *•> Bates, T. F., op. cit., p. 15. 
 
 material was drilled throtigh. Nearly all the drill holes 
 on the sides of the greenstone ridge passed through at 
 h^ast some laterite before encountering unaltered bedrock. 
 In most places, however, the presence of sand grains and 
 water-worn pebbles suggests strongly that much of the 
 laterite has been reworked or transported a short distance 
 and has become part of the lower lone beds. For example, 
 hole 24-3 was drilled through lateritic material from 144 
 feet to 220 feet, where greenstone was encountered. The 
 interval from 214 feet to 220 feet contained pebbles of 
 greenstone and quartz indicating that the laterite was 
 transjiorted after its formation. Laterite in a stream bed 
 about 1000 feet south of the "Woolford pit is definitely 
 residual, however, because the original texture and struc- 
 ture of the parent rock are still visible, including pheno- 
 crysts and small faults. 
 
 Six differential thermal analyses were made of samples 
 of laterite. Four Avere of definitely residual material and 
 two of material rcAvorked in the loAver lone member. All 
 the curves Avere Type I, Avith a suggestion of halloysite 
 in the two sedimentary laterites. The residual laterites 
 Avere picked to represent a range in the degree of 
 Aveathering. The least Aveathered sample Avas brownish 
 yellow Avith residual texture quite evident and Avould 
 more properly be called lithomarge. The production of a 
 Type I curve from each of these samples indicates the 
 very early formation of kaolinite in the process of lateri- 
 zation. 
 
 Allen ^^ and P>ates ■"•'' both believed that the laterite Avas 
 formed in pre-Ione time. The evidence from the Buena 
 Vista area shoAving that the laterite Avas eroded into the 
 loAvest beds of tlie lone format ioii aiul that the lone forma- 
 tion rests on laterite in many places agrees Avith this 
 conclusion. The basal loAver Tone beds in holes 7-1 and 
 18-2 are highly colored by iron oxides and the thermal 
 analy.ses give Type Ta (tending toAvard Type II) curves 
 Avhich Avould suggest strongly that laterite Avas a source 
 of part of the material in the beds. On the other hand, the 
 pre-Ione Eocene (?) sediments (Avhich are more fully 
 discussed in a folloAving section) give no suggestion of 
 intense tropical Aveathering, as they have a higher per- 
 centage of fresh feldspar, contain micas and chlorite, 
 and give Type II and III thermal curves. Only at its 
 contact Avitii the lone formation in hole 18-1 does there 
 appear to have been Aveathering of the upper several feet 
 of the pre-Ione Tertiary after deposition. In hole 7-1, 
 Avhere it OA-erlies greenstone, the greenstone is Aveathered 
 but not in a manner Avhich suggests laterization. Appar- 
 ently the pre-Ione Eocene (?) sediments Avere derived 
 from a source Avhere mechanical Aveathering predominated 
 over chemical Aveathering. This helps shoAV that the laterite 
 formed after the pre-Ione Eocene ( ?) Avas deposited and 
 before the basal loAver lone at Buena Vista Avas deposited 
 because the formation of laterite does not normally take 
 place Avhere erosion is rapid ; on the contrary, the presence 
 of laterite implies a long period of surface stability Avith 
 little erosion or deposition. 
 
 Mariposa Slate 
 
 The IMariposa slate is lu-edominautly black slate Avith 
 lenses of sandstone and conglomerate, and characteristic- 
 ally contains no interbedded volcanics. The Amador group 
 grades upAvard into the ]\Iariposa slate in most places and 
 
 ^ Allen, V. T., op. cit., p. nfll. 
 3-'' Bates, T. F., op. cit., p. 27. 
 
Tone Fok.matiox, Buexa Vista Akea 
 
 15 
 
 the contact marks the end of the Jurassic volcanism. The 
 IMariposa slate in adjacent areas usually occurs intricately 
 folded in synclines. No Mariposa slate crops out in the 
 Buena Vista area but it was found at the bottom of 
 hole 18-8. Althoufih it was weathered to pink to <ireenish- 
 jrray clay, the ori<:inal slaty deavajre is still apparent. 
 The dejrree of weatherinj*' is not that of complete tropical 
 weatherinjr such as the weatherinjr which has altered the 
 Mariposa elsewhere in the lone area. At Irish Hill, about 
 '.] miles northwest of the town of lone, for example, the 
 Mariposa slate has been completely weathered to very 
 Avhite clay. 
 
 Differential thermal analyses were made on four sam- 
 ple.s of weathered Mariposa slate from the bottom of hole 
 18-3, one sample of fresh black Mariposa slate from 
 Chili Bar in El Dorado County, and a sample of white 
 residual clay derived from Maripo.sa slate at Irish Hill, 
 near the town of lone. Althou<rh the curve for the fresh 
 slate showed a little carbon and jiossibly some chlorite, it 
 showed no clay minerals. The Irish Hill clay fiavc a Type 
 IT (tendin<r toward ITa) curve. The curves for the Buena 
 Vista area samples were intermediate between Types III 
 and Ilia. It is sijiuificant that the Irish Hill clay is appar- 
 ently at the end point for weatherin^jr of the tyi)e that 
 acted on the pre-Ione surface, and yet jrives a poor Type 
 II curve. This sujrjrests that the weathered products of 
 the Mariposa slate did not contribute sifrnificantly to the 
 Cheney Hill and Edwin clays of the lone formation. 
 
 Tertiary System 
 Eocene (?) Pre-Ione Beds 
 
 In the lower i)arts of .several of the Buena Vista drill 
 holes, the drill iufr pas.sed throujrh .sediments with litho- 
 lofjie characteristics of the lower lone member and into 
 sands and shales showin<r no evidence of intense weather- 
 in<r except near their contact. These beds are distiufruished 
 from the lower lone member by the ]>resence of biotite, 
 chlorite, and clays of Type III. Th'ese beds ai)pear to be 
 present alon*.' the north(>ast side and bottom of the Buena 
 Vista Basin as indicated by holes 7-1, 13-1, 13-2, 18-1, 18-2, 
 and 10-1. In none of the holes were they encountered at 
 a depth of less than 231 feet. Oeolojric map])in<r in other 
 parts of the lone rej^ion has not yet revealed outcrops of 
 any rocks which appear to be part of these beds. 
 
 Typical sections of the pre-Ione Eocene ( ?) were those 
 in hole 7-1 from 231 feet 4 inches to 2n9 feet 6 inches, in 
 hole lH-1 from 311 feet to 375 feet, and in hole 18-2 from 
 235 feet to 254 feet. These sections are jriven in the aji- 
 pendix. The section in hole 7-1 represents the full thick- 
 ness at that point but the sections in holes lS-1 and lS-2 
 were not drilled to bedrock, and at the contact with the 
 lower lone member in hole 18-1 the top of the pre-Ione 
 Eocene (?) is not definite. 
 
 Silty clay is the predominant rock, with beds of sandy 
 clay, sandy silt, and clay. Conglomerate composes less 
 than 10 percent of the beds. The colors of the sediments 
 are larjrely prays and jrreens, but a few yellow, brown, and 
 red beds were present in the weathered section in hole 18-1. 
 Almost the entire section in hole 7-1 is hi<;hly carbonaceous 
 but very little carboiuiccous matter was seen in any of 
 the other holes. In the center of the basin the sediments 
 all ran<?e from <>reeu to white, excejit in the weathered 
 zone. 
 
 The ratio of feldspar jrrains to quartz grains is three 
 to four times greater than was found in the lower lone 
 sand, which would indicate less severe weathering or more 
 rapid erosion of the source rocks than occurred dviring 
 lone time. Chlorite, biotite, and muscovite were also com- 
 mon detrital minerals in the samples checked. 
 
 In spite of the rapid lateral and vertical variation in 
 appearance of the sediments of the pre-Ione Eocene ( ?) 
 the clay minerals show a remarkable similarity. Thirteen 
 differential thermal analyses were run and all gave kao- 
 linitic curves of Types I la and III. Of the four curves 
 that were Type Ila, three were approaching Type III. 
 This similarity was not only very useful in correlation 
 but also shows the lack of development of clays of Types 
 I and II and woidd indicate mild weathering due to 
 climatic conditions or rapid erosion before extensive 
 weathering could take place. The results of one differen- 
 tial thermal analysis suggested the presence of some 
 montmorillonite-type clay in a bed of very dense tough 
 green siltstone in hole 10-1 ; however, kaolinite was also 
 present and gave a Type III curve. 
 
 The 28-foot 2-inch section in hole 7-1 was the oidy thick- 
 ness of the pre-Ione Eocene ( ?) sediments that was 
 measurable from its lower contact with bedrock to its 
 upper contact with the lone formation; however, this 
 section is on the side of the basin and the surface may 
 have been eroded an unknown amount. The thickest sec- 
 tion is apparently in hole 10-1, from the questionable 
 upper contact at a de])th of 2f)5 feet (12 feet above sea 
 level) to the point where the drilling was stopped at a 
 depth of 306 feet (110 feet below sea level), a total of 
 131 feet. 
 
 The base of the pre-Ione Eocene ( ?) sediments rests 
 with a very low dij) on weathered greenstone in hole 7-1 
 but was apparently not reached in any of the other drill 
 holes in the area. It probably rests on greenstone and 
 Mariposa slate everywhere in the deeper parts of the basin 
 unless .some older post-Jurassic formation exists below it. 
 
 An unconformity between the pre-Ione Eocene (?) 
 sediments and the lower lone is indicated at several places 
 along the contact. In hole lS-1 the upper 12 feet of the 
 j)re-l<)ne Eocene ( ?) sediments are highly weathered, but 
 in hole 18-2 there is only a very thin weathered zone 
 at the top, and in hole 7-1 there is none. Weathering of 
 this type, suggesting the beginning of laterization, would 
 indicate a period of time with neither deposition nor 
 erosion. "Weathering would be either general or else more 
 active on the higher slojx's which were more exposed to 
 alternate moisture. and relative dryness. The absence of 
 a highly weathered zone in hole 7-1 indicates that there 
 may have been subse(iuent erosion before the overlap of 
 the lone sediments. Although the sediments of the pre- 
 Ione Eocene ( ?) were not derived from a source under- 
 going intense laterite-forming weathering, the laterite was 
 present at the beginning of lone deposition. The laterite 
 served as a source of material for the basal beds of the 
 lower lone, and re(piire(l an interval between the pre- 
 Ione Eocene (?) and lower lone deposition for devel- 
 opment. 
 
 The pre-Ione Eocene (?) beds cannot be correlated 
 definitely with any other geologic nnit on the basis of 
 our present knowledge. Howev(>r. the lone formation is 
 underlain in manv other areas bv units which bear a 
 
16 
 
 Sri:ciAL Kepoht 1!) 
 
 litholo<i-ic rcsemblanoo to tlie pro-Iono Eot-cno ( ?) bods 
 of the Bnena Vista aroa. Piper''" states that "wherever 
 the lone formation erops out in the Mokelumne area it 
 rests directly npon the pre-Cretaeeous crystalline rocks. 
 In a few deep wells, however, and in outcrops at several 
 districts in central California it appears to be underlain 
 by sray micaceous shale and sand that constitute a dis- 
 tinct stratigraphic unit." 
 
 The nearest point to the Buena Vista area that Piper 
 refers to is the well he calls Well 4712A1 (Allen's Clem- 
 ents well) which went through a sedimentary bed at a 
 depth of 1779 to 197,i feet, just below the lone. This bed 
 was "chiefly dark gray to brown shale and gray sand, 
 mostly fine, contained many fossils, and included carbona- 
 ceous streaks or flakes. " "*^ 
 
 Stewart ^^ describes the "Dry Creek" sandstone mem- 
 ber of the lone formation at Sutter Buttes as "a silty, 
 micaceous, fine sand.stone with plant remains and massive 
 fossils. ..." 
 
 Allen "'^ discusses the gray Walkup clays, below the lone 
 formation at Lincoln, and "the Dry Creek formation" at 
 Oroville Table Mountain, composed of gray shales overlain 
 by biotite sandstone. The age of the Walkup clay,'"' the 
 Marysville formation, ^^ the "Dry Creek" sandstone mem- 
 ber of the lone,'*- and the gray shale under the lone in the 
 Clements well ^-•' have been considered middle Eocene. 
 Paleontologic examination of a suite of samples of pre-Ione 
 sediments by Standard Oil Company of California showed 
 them to be barren of microfauna.*-'^ 
 
 No definite correlation between these middle Eocene 
 formations and the pre-Ione Eocene ( ?) beds of the Buena 
 Vista area can be made as no fossils Avere found in the lat- 
 ter but we believe that the stratigraphic aiul lithologic evi- 
 dence is sufficient to consider the beds tentatively to be 
 Eocene. 
 
 Eocene lone Formation 
 
 The lone Avas originally named by Lindgren,'*'' and the 
 type area around the toAvn of lone, including the Buena 
 Vista area, was described by Turner, ^^ who distinguished 
 three divisions in the formation. From oldest to youngest 
 they were : 
 
 1. White clay, some portions sandy, containing lignite. 
 
 2. Sandstone, passing into conglomerate in places. Us- 
 ually Avhite but red in one place. 
 
 3. Clay rock. 
 
 Allen "*"' restricted the name lone formation to the beds 
 along the foothills of the Sierra Nevada that have a min- 
 eral composition and history similar to the lower two mem- 
 bers of the formation at the type locality. The beds are 
 shown as Euc on the geologic map of California.^" 
 
 •■» Piper, A. M., op. cit, p. 85. 
 
 »' Ibid. 
 
 '^ Stewart, Ralph, Lower Tertiary .stratigraphy of Mount Diablo, 
 
 Mary.sville Butte.s, and west border of Lower Central Valley of 
 
 California: U. S. Geol. Survey Oil and Gas Prelim. Chart 3 4, 
 
 Sheet 2, 1949. 
 ™ Allen, V. T., op. cit., pp. 3G4-368. 
 '" Ibid., p. 3G4. 
 " Ibid., p. 366. 
 
 *- I>icker.'<on, R. E., op. cit. 1916, p. 3X,S. 
 Clark, B. U, op. cit. 1921, p. 12.'.. 
 Stewart. Ralph, op cit. 
 <■-■< Allen, V. T., op. cit., pp. 402-403. 
 ^-'' Ha.stinf?.'^. D. D., and .Stone, Charity AL, personal coniinunication. 
 
 May 19.) 2. 
 ■••' Lindgren, W'aldemar. IT. S. Oeol. Survey Geol. Atlas, Sacramento 
 
 folio (no. 5), p. 3, 1894. 
 ■" Turner, H. AV., op. cit. 
 '■■ Allen, V. T., op. cit., pp. 353-35 4. 
 <" Jenkins, O. P., Geologic map of California: California Div. Mines, 
 
 scale 1 :500,000, 1938. 
 
 FiGi'RK 12. AVoolford clay pit. AVIiito jirpa in right center is 
 
 Cheney Hill clay. Overburden is white, hulT, and brown sandstone 
 
 and conglomerate. The pit is now idle. 
 
 During the Avork on the Buena Vi.sta area the geologic 
 mapping, the study of drill cores and thin sections, and 
 the ceramic tests shoAved that there are two major map- 
 pable units, separated by an unconformity and lithologic ; 
 differences, in the lone formation as described by Allen. 
 These two units are defined as members. The upper and 
 loAver boundaries of the Tone formation remain the same , 
 as the boundaries of the lone formation defined by Allen. 
 
 Lower lone Member. The older of the tAvo units in the 
 lone formation is characterized by a high proportion of 
 ({uartz to feldspar, and clay minerals that give dift'erential 
 thermal curA'es of Types I, la, II, and Ila ; and by the ab- 
 sence or rarity of biotite, chlorite, and clay minerals that 
 give differential thermal curves of Types III, Ilia, or Illb. 
 
 It is proposed that the name "loAver lone" member be 
 used for the loAver unit of the lone formation. ' 
 
 The loAver Tone member crops out over large areas north 
 of Jackson Valley, bwt continuous sections are not found 
 in most places and Avhatever sections are measurable usu- 
 ally yield data on relatively short stratigraphic sections 
 only. The most complete and typical sections available are 
 those shoAvn in the drill-hole logs published Avith this pa- 
 per. Lateral A'ariation prevents any section from bearing 
 more than resemblance to any other section but holes 18-1 
 and K-10 are together considered to giA'e the longest and 
 most representative section of the loAver lone. The type 
 section of the lower lone member Avas chosen as the inter- 
 vals from 10 feet to 42^ feet in hole K-IO and from 109 feet 
 to :511 feet in hole 18-1. The lignite at the bott(mi of hole 
 K-10 is believed to be the same lignite as the one at 109 
 feet in hole 18-1 and the t.vpe section tlierefore represents 
 a tliickness of 234 feet of loAver lone .sediments. 
 
 In the Buena Vista area there are three recognizable 
 units or lentils in the loAver lone. These are a loAver lentil 
 Avhicli consists in-edominantly of clayey sand, in many 
 l)lac('s colored gray by carbonaceous matter but con- 
 taining only a few A'ery thin partings of lignite ; an inter- 
 mediate lentil Avhich is made up largely of clay and 
 lignite Avith minor amounts of clayey sand and contain- 
 ing three distinct lignite beds; and an upper lentil of 
 clayey sand and sandy clay locally called the lone sand 
 and Cheney Ilill clay. The commercial lignite from this 
 area is all in the middle lentil ; the Fancher, Woolford, 
 and Kaolin-Fye clay and sand pits are in the upper lentil. 
 
loNE Formation, P>rENA Vista Ahka 
 
 17 
 
 l"'i(;i KK l.S. l'";iiicli('r cliiy pit. Cliciicy Hill •■Iji.v lar^jcly liidili'ii l>y caviiic. Overlnirdcn is lirciwn sniidstono of llio upper loiip member and 
 
 Quaternary terrace gravels. Camera l)earin}; northeast. 
 
 Tho niiiHM'Hl assciiiblajro of tlio lower loiic inoiiibor is 
 characterized by the ab.sence or rarity of Jiiiiierals .such 
 as biotite, plaj^Moclase, and chlorite that do not persist 
 throufrh intense weathcrintr. There are some nmscovitc 
 flakes in the lower part of the lower member, however. 
 The three clay types in the lower lone of the Buena Vista 
 area that have been {riven names by the local miners are 
 the Edwin clay, Cheney Hill clay, and lone sand. The 
 lone sand is a (jiiartz sand with 2.') to SO jx'rcent kaolinite 
 and anaiixite. The color of the lone sand raiifrcs from 
 white thron<rh brown to red because of iron oxide stains. 
 It crops out in the eastern part of the area and is re- 
 ported from wells in the central part of the arca.^' 
 Farther west, away from tlie source of the sediments, is 
 the sandy ("hcney Hill clay. The Cheney Hill clay and 
 the lone sand are apparently in the same strati{j:rai)iiic 
 position and all <;radations are found between the lone 
 sand of the Kaolin-Fye pit ami the Cheney Hill clay of 
 the Fancher pit. The (,'heney Hill clay seems to represent 
 a finer-g:raine(l phase of the Tone sand farther from the 
 source of sediment supply. Bates'*** points out the simi- 
 larities between the Etlwin and Cheney Hill clays aiul 
 considers the Edwin a nearly sand-free variety of tlie 
 Cheney Hill clay. Our work did not bear this out but 
 instead showed the Edwin clay of tliis area to be in the 
 lower lentil and the Cheney Hill clay to be in the up])er 
 lentil of the lower lone member. 
 
 Allen ^■' showed that the larjrc i)early tlakes of clay 
 mineral, which are almost r(>stricted in California to the 
 lone formation or its e(|uivalent, are anauxite. Anauxite 
 is present tlirou<jrhont the lower and upi)er lone but is 
 especially common in the lone sand in which it com- 
 prises a larfje proportion of the clay fraction. 
 
 Several beds in the lower lone are colored by iron 
 oxides. Some of the iron was ai)parently derived from 
 laterite eroded from the {greenstone rid{,'e or from {green- 
 stone and similar rocks in the hi{,dier Sierra Nevada. All 
 alon{? the flanks of the prreenstone ridgre lar{;e (piantities of 
 lateritic material have been reworked into the base of the 
 lower lone, and in many places it is distin{;'uishablc from 
 
 ''■ Faneher, Jack, personal comnuiiiication, r.i."il. 
 ■•- Hates, T. V., op. cit., pp. 2.'')-2(i. 
 <" Allen, v. T., o]). cit., pp. .•i77-.'!7S. 
 
 laterite still in place only by the sedimentary sand {grains 
 or pebbles in some beds or by non-lateritic beds lower in 
 the section. 
 
 A different type of iron-oxide colorin{j: is foiuid at the 
 upper surface of the lower Tone Avhere clays and sands 
 crop out or are overlain by terrace {jravels. Commonly at 
 these places there are heavy concentrations of iron oxides 
 as colorin*; material and as concretions. 
 
 A lar<,'e number of differential thermal analyses were 
 made on samples from all parts of the lower lone. These 
 showed the differences between the lower lone and other 
 formations of the area, and the less distinct but never- 
 theless si{rnificant differences between the three lentils 
 of the member. 
 
 The lower lone clay minerals consistently {rave Type T 
 and Ty])e 11 ctirves and variants of these curves. Only 
 one sample, from near the base of the formation, {jave a 
 Type 111 curve. Clays which {rave a Tyjie I curve were 
 common, especially the Edwin and Cheney Hill clays 
 Avliich almost invariably {rave Ty])e I curves. 
 
 Allen •■■" believed that the ])hysical and chemical prop- 
 erties of the Edwin Clay su{r{rested the presence of the 
 clay mineral halloysite. Bates,''^ after detailed study, 
 concluded that the Edwin clay was kaolinite. Differential 
 thermal analyses on several samples of ?]dwin and Cheney 
 Hill clays from the Buena Vista area showed kaolinite 
 with a tendency toward halloysite. 
 
 Tn the lower Tone the clays are usually Type T on the 
 southwest side of the basin and are. by comparison, a 
 mixture of Types I and 1 1 on the northeast side. In several 
 individual beds which were traced throu<rh a number of 
 holes the differential thermal analyses approached Type I 
 in the hi{rher parts of the basin and Type lla in the center 
 of the basin. Similarly, there is a <;reater thickness of 
 solid, pure li{rnite toward the mar{rins of the basin than 
 in the center. Clays close beneath li{rnite {lenerally {zave 
 differential thermal analyses api)r()achin<r Type I more 
 closely than did c-lays farther below li-rnite. This apparent 
 relation betw<M'n liouitc and clays approachin{:' Type I 
 su{r}rests that the clays w(>re altered by or{ranic solutions 
 from the ()verlyin<r- 1i<:nite after deposition. Evidence in- 
 
 •" Alhn. V. T., op. cit., pp. ."l.SO-SSS. 
 •■•' Bates, T. F., op. cit., p. 17. 
 
18 
 
 Special Report 10 
 
 dicates this alteration of lower lone sediments was an 
 important factor in producing the present assemblage of 
 clay minerals. 
 
 The lower lone member underlies most of the Buena 
 Vista area except along the crest of the greenstone ridge. 
 It crops out along the flanks of the greenstone ridge and 
 on the north side of Jackson Valley east of the Fancher 
 clay pit. The main outcrop area to the north is entirely in 
 the upper lentil of the lower lone. 
 
 No definite lower lone beds were found around the base 
 of Buena Vista Peak and the drill-holes there do not 
 seem to have reached it. The Buena Vista coal mine, at 
 an elevation of about 300 feet on the south edge of Jack- 
 son Valley, due south of Buena Vista, is reported ''^ to 
 have reached gray clay at a vertical depth of 50 feet and 
 lignite at 5fl^ feet. The gray clay is probably lower lone 
 and the lignite is certainly lower lone. 
 
 The thickest single section of the lower lone is in hole 13- 
 2 with an interval of 285 feet between the upper lignite and 
 the apparent contact with the pre-Ione Eocene ( ?) beds. 
 The upper lentil, which is not represented in hole 13-2, is 
 in places about 130 feet thick, although the measurement 
 of the section is an estimate because of lack of topographic 
 control in some of the area. This would give a total maxi- 
 mum thickness of 415 feet. The thickness of the type sec- 
 tion is 234 feet. There is a range of thickness due to thin- 
 ning along the margins of the basin and to removal of 
 portions of the upper lentil by erosion. 
 
 The sediments of the lone formation have been shown 
 by Lindgren ''^ to have originated from the basement 
 rocks of the Sierra Nevada. He was the first to show that 
 the pre-volcanic gravel channels represented the beds of 
 the rivers that had emptied into the lone sea and pointed 
 out the continuity of the auriferous gravels with the lone 
 sands and clays. Lindgren ''* traced the major Tertiary 
 pre-volcanic rivers and found that the Tertiary Mo- 
 kelumne River mouth was about 12 miles north of Buena 
 Vista and the Tertiary Calaveras River mouth was 9 
 miles to the south. These two large rivers phis many 
 streams, emptying into the sea at intermediate points, 
 probably furnished the lone sediments now found in the 
 Buena Vista area. One such small stream formed a gravel 
 delta about 3 miles north of the area. Jenkins •'••' has illus- 
 trated the relationship between the auriferous gravels 
 and the lone formation. Bates '"''"' studied quartz grain in- 
 clusions in the Cheney Hill and Edwin clays and felt 
 that a large proportion of the quartz grains were from 
 the granitic rocks of the Sierra Nevada. 
 
 The lower lone member rests with an api)arent un- 
 conformity on the pre-Ione Eocene ( ?) beds, as noted in 
 the previous section, and underlies the upper lone member 
 with a definite \inconformity. At the Fancher pit coarse 
 brown upper lone .sand with abundant biotite grains un- 
 conformably overlies the Cheney Hill clay. The contact 
 is irregular and dips to the south. In several places in 
 the area, such as in the drill holes west of the greenstone 
 ridge, southeast of the Woolford pit, and at the Fancher 
 pit, upper lone sediments occur in positions that are 
 
 ^' Logan, C. A., Sacramento field divi.sion — Amador County : California 
 
 Min. Bur. Kept. 2.3, p. 146, 11)27. 
 " T^indgren, Waldemar, Tertiary gravel.s, op. cit., p. 24. 
 s< Il)id., plate 1 and fig. .3. 
 s^ Jenkins, O. P., Geology of placer depcsit-s : California Div. Mines 
 
 Bull. 1.35, 2nd ed., fig. 64, p. 176, 1950. 
 "> Bates, T. P., op. cit., pp. 28-30. 
 
 topographically lower than adjacent or nearby lower lone 
 beds. The relationship is such as to indicate that the upper 
 lone beds were deposited on an irregular erosion surface 
 formed on the lower lone beds. 
 
 No direct evidence of the geologic age of the lower lone 
 was found in the Buena Vista area but the formation can 
 be correlated with lone exposures in other regions where 
 age determinations are possible. 
 
 The mineral analyses given by Allen ^"^ for lone forma- 
 tion samples from various points along the east side of 
 the Great Valley indicate that lower lone lithology is 
 found from Butte County to Madera County. INIineral 
 analyses ^'^ of the lone formation at Chalk Bluffs, Nevada 
 County indicate that the beds considered by MacGinitie 
 as lone are probably the lower lone member. They are 
 overlain unconformably by pre-volcanic sediments with 
 biotite and a high percentage of feldspar which are prob- 
 ably the upper lone member. 
 
 Stewart ^'^ considers a formation above the Meganos at 
 Rio Vista and north of Mount Diablo to be questionable 
 lone. 
 
 The lone formation sediments are largely deltaic or 
 lagoonal and fossils are rare. In the few localities where 
 marine fossils occur, the material is poorly preserved and 
 identifiable specimens are scarce. Fossils from the lone 
 formation at the Buena Vista stone quarry, about 3 miles 
 southeast of Buena Vista, have been identified by Clark *^^ 
 as IMeganos (middle Eocene) types. Stewart*"'^ considers 
 the Meganos as lower Eocene, however, and places the lone 
 above it in the middle Eocene. MacGinitie,"- on the basis 
 of work on the fossil flora of the Lower lone at Chalk 
 Bluffs, correlates the lower lone with the Capay of the 
 Coast Ranges. 
 
 Upper lone Member. The younger of the two units in 
 the lone formation is characterized by a generally higher 
 proportion of feldspar to quartz than in the lower lone 
 and by the presence of biotite, chlorite, and kaolinitic clay 
 minerals that give differential thermal curves of Types II, 
 Ila, III, and Illb; and by the absence of kaolinitic clay 
 which would give the differential thermal curve of Type I. 
 It is proposed that the name "upper lone" member be 
 used for the upper unit of the lone formation. 
 
 North of Jackson Creek, the upper lone member crops 
 out below the terrace gravels on the lower hills west of 
 Buena Vista. The lower slopes of Buena Vista Peak are 
 also composed of upper lone sediments. Upper lone was 
 intersected in several of the drill holes along the green- 
 stone ridge. The thickest section of definitely upper lone 
 beds is on the north slope of Buena Vista Peak but it is 
 so sandy and unconsolidated that surface exposures are 
 rare. Chosen as a type section of the upper lone, is the 
 section through which hole B. V. 5 was drilled, and ex- 
 tending above the hole to the base of the Valley Springs 
 formation. The vertical distance from the base of the 
 Valley Springs formation at an elevation of about 475 
 feet, to the bottom of hole B. V. 5 at an elevation of about 
 312 feet, represents approximately 163 feet of upper lone 
 
 •'■' Allen, V. T., op. cit, p. 375. 
 
 ^"MacGinitie, H. D., A middle lOocene flora from the central Sierra 
 
 Nevada: Carnegie In.st. Wa.shington Pub. 534, pp. 13-23, 1041. 
 ■"•" Stewart, Ralph, op. cit. 
 
 "" Clark, B. L., personal communication in Allen, V. T., op. cit., p. 358. 
 "' Stewart, Ralph, op. cit. 
 »2 MacGinitie, H. D., op. cit., pp. 28 and 91. 
 
loNE Formation, Buena Vista Akea 
 
 19 
 
 FiGiRJ-; 14. Kaoliii-Fye saiul pit. White Imie siiml with ovprbiirden 
 
 of buff lone saiul and Quaternary terrace gravel. Camera bearing 
 
 north-northwest. 
 
 sediments. The hole, however, does not reach the base of 
 the upper lone member. The upper lone, below tlie bottom 
 of hole H. V. 5 has poor surface e.xposure, and other holes 
 in the vicinity do not frive additional information, so these 
 lower beds are not included in the type section. 
 
 The upper lone member is predominantly sand and 
 clayey sand, with a little clay and minor amounts of 
 coufrlomerate. No lifrnite is present but some of the clays 
 contain enoujrh carbonaceous material to be chocolate 
 colored. The clays persistently have a <?reenish color that 
 is rare in the lower lone. 
 
 Biotite was almost universally present in the samples 
 checked, and chlorite was common. Feldspar comprised 
 i'rom 20 to 25 percent of the sand frrains and is, therefore, 
 two to three times as abundant as in the lower lone. 
 
 Two lentils in the upper Tone member are i)ersistent 
 over most of the area. One is the hard white or jrray sand- 
 stone at the top of the formation. This sandstone was re- 
 ferred to by II. W. Turner '■•' as the middle member of the 
 lone formation and by Piper "^ as the upper member of the 
 
 ■" Turner, H. W., op. oit. 
 
 •* Piper, A. M., op. cit., p. 80. 
 
 T(me formation. It crops out on the northwest side of 
 Buena Vista peak, on top of a hi<>h hill about 3000 feet 
 east of the Woolford pit, on top of Chitwood Hill, and on 
 a small hill about one-half mile Avest of Chitwood Hill. The 
 hard .sandstone is cross-bedded in places and has a typical 
 upper lone mineral assemblage except that the clay min- 
 eral matrix is largely anauxite in wormlike and fan- 
 shaped aggregates. The other persistent unit is the Chit- 
 wootl clay that was mined at the Chitwood pit. It also crops 
 out 500 feet .southeast of the Fancher Pit and in the can- 
 A-on on the west side of Buena Vista Peak. It is about 70 
 
 KIOCKK l.">. Wa.\-extraction plant for the removal of .Monlan wax 
 
 from lignite, o|)erate(l l).v American Lignite l'ro(lu<-ts Company. 
 
 Type section of the upper lone nieml»er is on the bill l)eyon<l the 
 
 plant. Camera bearing south-southwest. 
 
 l-'UMKK ](». Sec(iou at J'aii<-lier day pil in laved drift 
 at north end of main face. Cheney Hill clay overlain by 
 brown sandstone of the upper lone nieinlier and Quater- 
 nary terrace gravel. The pit is now idle. 
 
 percent sand, MO percent clay, contains no anauxite, and is 
 usually gray in color. The clays and sands between and 
 below these two members are so lenticular that only very 
 tentative correlation cotdd be made between the various 
 drillholes on the north slope of Buena A'ista Peak. 
 
 A large innnber of differential tiiennal analyses were 
 made of samples from various parts of the upper lone. Dif- 
 ferential thermal analyses of upi)er lone samples did not 
 ajiin-oach standard kaolinite closer than Type II (tending 
 toward la), and most of the samples gave differential 
 thermal analy.ses of Types III and Illb. 
 
 A tendency for the differential thermal curves to aji- 
 l)roacli Type I toward the top of the formation was indi- 
 cated, with the closest approach. Type II curves (tending 
 toward la) in the Chitwood clay and the hard sandstone. 
 
20 
 
 Special Report 19 
 
 This development of the kaoliiiitic minerals toward kao- 
 linite may be the result of weatherinp: on the upper part of 
 the formation durin<2; the interval between the close of the 
 deposition of the upper lone member and the beginning of 
 the deposition of the Valley Springs formation. 
 
 The surface on which the upper lone member was de- 
 posited was irregular, and extensive erosion has taken 
 place since it was deposited. Because of this, the upper 
 lone member has a large range in thickness throughout 
 the area. In the vicinity of the type section the base of the 
 upper lone member is not exposed but the shaft of the 
 Buena Vista coal mine, with the collar about 300 feet in 
 elevation, reached lower Tone lignite at a vertical depth of 
 59^ feet "'' and 9| feet of gray clay above the lignite is prob- 
 ably also in the lower lone member. The elevation of 250 
 feet is then the lowest probable elevation for the base of the 
 upper lone member. The thickness of the upper lone mem- 
 ber in the vicinity of the type section is thus more than 163 
 feet and less than 225 feet. At Chitwood Hill the upper 
 lone beds rise 130 feet above the valley floor with no evi- 
 dence of lower lone beds at the base. At the high hill 3000 
 feet east of the "Woolford pit, 70 feet of i;pper lone sedi- 
 ments rest on lower lone beds and in the valley to the 
 southwest there are an additional 50 feet of upper lone 
 sediments. 
 
 The source of the upper lone sediments was probably 
 the crystalline rocks of the Sierra Nevada. The effects of 
 weathering were not as prominent as in the lower Tone 
 member, either because the climate had become less trop- 
 ical or because erosion was proceeding too rapidly to allow 
 deep weathering. No marine upper lone beds were recog- 
 nized in the area, but there is a hard red sandstone con- 
 taining marine fossils a mile and a half east, which ap- 
 pears to be the same sandstone that is at the top of the 
 upper lone type section. 
 
 The contact between the upper and lower lone members 
 is irregular and obviously an unconformity. The maxi- 
 mum differential relief measurable on the erosion surface 
 is about 130 feet in the region east of the Fancher Pit. The 
 upper surface of the upper lone member was also deeply 
 eroded before the deposition of the Valley Springs forma- 
 tion. In the small canyon west of Buena Vista Peak the 
 base of the Valley Springs formation has a difference in 
 elevation of 85 feet over a distance of 400 feet. 
 
 Sands with upper lone lithology have been described in 
 or above the lone formation at several points on the east 
 side of the Great Valley and in the Sierra Nevada. Allen "" 
 described outcrops near Valley Springs and at Knights 
 Ferry as follows : 
 
 "One mile west of Valley Springs is a small sandstone 
 quarry. The sandstone contains, in addition to anauxite 
 and quartz, altered biotite and more feldspar than is in 
 the usual lone sandstone. It probably should receive a 
 separate name, as the mineral assemblage is not typical, 
 but the outcrop is small and hardly warrants it." In 
 describing a section at Knights Ferry, he says "^ "Sev- 
 enty feet of cross-bedded sandstone forms the upper part 
 of the section. This sandstone contains biotite and about 
 30 percent of orthoclase, and like the sandstone at Valley 
 Springs probably should have a separate name, but for 
 the same reason a name has not been given." 
 
 *•'• Logan, C. A., op. cit. 
 
 » Allen, V. T., op. cit., p. 3.59. 
 
 «' Ibid. 
 
 At Chalk Bluffs, MacGinitie "^ found about 100 feet of 
 ' ' biotite sands ' ' followed by 22 feet of conglomerate over- 
 lying sediments with lower lone lithology and under- 
 lying the rhyolite series. lie described them as rusty, 
 cross-bedded, quartz-biotite sands with fresh feldspar. 
 He also refers ''" to biotite sands below tuffaceous yellow 
 clay in the Cherokee hydraulic pit at Oroville Table 
 Mountain, Butte County, and correlates them with the 
 biotite sands at Chalk Bluffs. 
 
 The lithology and stratigraphic position of the biotite 
 sands at Valley Springs, Knights Ferry, Cherokee, and 
 Chalk Bluffs are the same as the lithology and strati- 
 graphic position of the upper lone member at Buena 
 Vista and there is no reason to doubt that they may 
 be correlated. 
 
 No direct evidence of the age of the upper lone member 
 was found in the area. However, Allen ""^ considered the 
 marine sandstone of the Buena Vista quarry to be part 
 of the upper member of his lone formation, which is ap- 
 parently the same as the sandstone at the top of the type 
 section of the upper lone member. This sandstone con- 
 tains fossils identified as of middle Eocene age.'^^ If this 
 fossil zone is at the top of the upper lone member then 
 that member is certainly Eocene in part, at least. 
 
 Miocene (?) Valley Springs Formation 
 
 The Valley Springs formation was defined ''- as rhyo- 
 lite-containing beds with no fresh andesitie material and 
 as being stratigraphically above the non-volcanic lone. 
 The type section is an exposure on the west slope of 
 Valley Springs Peak, near Valley Springs, Calaveras 
 County. The lower beds in the Buena Vista area are 
 altered to greenish-buff clay and are the clay rock origin- 
 ally included in the lone by II. W. Turner." A bed of 
 coarse, erosion-resistant conglomerate, not far above the 
 base of the formation, was originally mapped as part of 
 the Pleistocene shore gravels,'^ but Piper '^^ presented evi- 
 dence for its inclusion in the Valley Springs formation. 
 
 Sediments containing fresh rhyolitic material crop out 
 on Buena Vista Peak above an elevation of 400 to 450 
 feet. A regional di]) to the northwest carries the base 
 down to about 250 feet along the crest of the greenstone 
 ridge, and almost all of the hills west of the ridge are 
 composed of Valley Springs sediments. 
 
 On Buena Vista Peak the Valley Springs formation is 
 predominantly clay rock, with beds of coarse conglom- 
 erate, capped" by 60 to 70 feet of hard vitreous rhyolitic 
 tuff.'" To the west, only a small proportion of the for- 
 mation is clay rock, and the rest is unconsolidated 
 greenish-tan or greenish-buff sands and one bed of con- 
 glomerate. A mesa about 3000 feet long and 1000 feet 
 wide, just east of Buena Vista Peak, is capped by a bed 
 of coarse, hard conglomerate 10 to 20 feet thick. Neither 
 Piper '" nor we found any Tertiary andesite in this con- 
 glomerate, so apparently it is part of the Valley Springs 
 
 «s MacGinitie, H. D., op. cit., p. 14. 
 
 o» Ibid., p. 28. 
 
 •"Allen, V. T., op. cit., pp. 357-358. . 
 
 '" Clark, B. L., personal communication in Allen, V. T., op. cit., 
 
 '2 Piper, A. M., op. cit., pp. 71-72. 
 
 " Turner, H. W., op. cit. 
 
 " Ibid. 
 
 '■' Piper, A. M., on. cit., pp. 57 and 72. 
 
 '8 See Turner H. W., Further contribution.s to the geology 
 
 Sierra Nevada: V. S. Geol. Survey 17th Ann. Kept., pt. 1, 
 
 1896 for a chemical analysis of this rock. 
 " Piper, A. M., op. cit., pp. 57 and 72. 
 
 358. 
 
 of the 
 p. 721, 
 
loNE Formation, Buena Vista Area 
 
 21 
 
 formation and not a Quaternary terrace gravel. Although 
 most of the rhyolitic glass in the lower beds has been de- 
 vitrified, a few small masses of rhyolite tuif are still 
 glassy. One such rock body crops out on the county road 
 about 700 feet south of hole 24-7. 
 
 Only four differential thermal analyses were made of 
 material from the Valley Springs formation. This was not 
 a sufficient number to establish any curve types as char- 
 acteristic of the formation. Three of the curves were Type 
 III (tending toward Ilia) and one was Type II (tending 
 toward Ila). 
 
 In most of the area the thickness of the Valley Springs 
 formation has been reduced by erosion so that only the 
 lower beds are present, but on Buena Vista Peak the base 
 of the Valley Springs formation ranges in elevation from 
 300 feet to 475 feet and the top of the highest bed is 848 
 feet. The maximum thickness is therefore about 458 feet. 
 The range of 85 feet in the elevation of the base in a small 
 area indicates differential erosion during the interval be- 
 tween lone and Valley Springs sedimentations, and the 
 l)resence of an unconformity. 
 
 The source of the rhyolite was considered by II. W. 
 Turner '^^ to lie to the east in the higher parts of the 
 Sierra Nevada ; Piper "^ traced the source from the 
 higher Sierra Nevada by way of channels that followed 
 the valley of Lindgren's Tertiary Calaveras River. ^" These 
 cliannels emptied into a basin at the present position of 
 \'alley Springs and the .sediments spread out north and 
 south. The Buena Vista area was on the northea.stern 
 edge of the area of original deposition as outlined by 
 Piper. 
 
 Gale^' ". . . feels that (the Valley Springs formation) 
 may be correlated tentatively with deposits of somewhat 
 similar composition that extend across the California 
 Trough into the Coast Ranges. Thus, although coinci- 
 dence has not been proved, it seems likely that the well 
 known marine Salinas shale of the ^Monterey group in the 
 Coast Ranges is not only derived from the siliceous rocks 
 and products of tliis epoch but throughout a wide area in 
 1he Pacific Border province actually includes tuffs that 
 represent the epoch of rhyolite volcani.sm." 
 
 MacGinitie,*^ on a basis of fossil flora, correlates the 
 Valley Springs with the San Pablo formation, and says it 
 is uppermost Miocene or possibly lower Pliocene. 
 
 Quaternary System 
 Terrace Deposits 
 
 Coarse-grained conglomerate eemented by clay, rests 
 on the tops and flanks of most of the hills north and north- 
 west of Buena Vista and on some of the lower hills south 
 of Jackson Creek. The cobbles in the conglomerate are 
 very well rounded and are as much as 12 inches in 
 diameter. Most of the cobbles are siliceous metamorjihic 
 rocks of the type present in the Calaveras formation, but 
 some are white vein quartz or, rarely, Tertiary andesite. 
 The matrix is usually greenish-brown to red-brown sandy 
 clay. The terrace gravels contain gold and have been 
 extensively mined wherever water was available. 
 
 « Turner. H. W., The rocks of the Sierra Nevada : II. S. Geol. Survey 
 
 14th Ann. Rept., pt. 2, p. 485, 1894. 
 '» Piper, A. M., op. cit., pi. 5. 
 "LindBren, Waldemar, The Tertiary Kravel.s of the Sierra Nevada of 
 
 California: U. S. Geol. Survey Trof. Paper 73, pi. 1, 1911. 
 "Gale, H. S., in Piper, A. M., op. cit, pp. 79-SO. 
 ""MacGinitie, H. D., op. cit., p. 28. 
 
 Figure 17. Chitwood clay pit and Chitwood Hill. Kntin- hill is 
 
 composed of upper lone sediments. The hard sandstone at the top 
 
 of the member is on the top of the hill. I'it is now idle. Camera 
 
 bearing northeast. 
 
 The conglomerates are a thin veneer on terraces whose 
 heights range from a few feet above the level of Jackson 
 Valley to over 400 feet to the north and on the flanks of 
 Buena Vista Peak. Measured thicknesses ranged from 
 1 foot to 18 feet. A much greater thickness was indicated 
 in many places by the mapping but this was usually the 
 result of sliding and creeping of the gravel down over 
 lower beds and of the complete covering and masking of 
 a number of terraces arranged in step-pattern on hillsides. 
 
 The area is in what Piper ^^ calls the Arroyo Seco 
 dissected pediment. The pediment was eroded to approxi- 
 mately its present form during the Victor epoch. The 
 terrace deposits of the area are not high enough, in most 
 places, to have rested on the original surface of the pedi- 
 ment nor are they low enough to be correlated with the 
 Victor formation which, in this area, is at the level of 
 the floor of Jackson Valley. They were probably formed 
 during the Victor epoch by the rivers which dissected this 
 portion of the Arroyo Seco pediment. 
 
 M Piper, A. M., op. cit., pp. 21-22, 28-29. 
 
 Fkjikk is. Cliilw I day south of Fancher |iit. Tiie clay is hard 
 
 enough to have been used l>y Indians for grinding nuts and seeds. 
 
22 
 
 Special Report 10 
 
 Recent Alluvium 
 
 Alluvium is constantly beinj-' deposited and reworkeil 
 alon<i- Jackson Creek and its tributaries, and durin": major 
 floods it is bein<i: added to the floor of Jackson Valley. It 
 is thin over most of the area but, from drill hole evidence, 
 it may reach a thickness of 25 to 50 feet in parts of Jack- 
 son Valley. At Buena Vista Bridjre on Jackson Creek 
 there is 5 feet to 10 feet of dark red-brown clayey allu- 
 vium immediately below the surface followed by 4 feet to 
 10 feet of auriferous red or preen sandy or clayey con- 
 jjlomerate with cobbles up to 6 inches in diameter. The 
 confrlomerate is like the present stream p-ravel and is cross- 
 bedded and channeled. There is little organic matter 
 compared to the soil above. 
 
 GEOLOGIC HISTORY 
 
 The oldest rocks that crop out in the area are the meta- 
 morphosed andesites and associated rocks of the Amador 
 group, which were deposited during the ITpper Jurassic 
 on the already folded and metamorphosed sediments of 
 the Paleozoic Calaveras formation. At the close of the 
 Amador volcanism, sedimentation contimied, forming the 
 Mariposa slate. These formations were folded in Tapper 
 Jurassic ^^ time to form the ancestral Sierra Nevada. Meta- 
 morphism took place during the folding and during the 
 subsequent batholithic intrusion. Erosion gradually re- 
 duced the height of the mountains and furnished sedi- 
 ments for Jurassic, Cretaceous, and early Tertiary beds to 
 the west. By Eocene time the mountains were low but the 
 rivers had sufficient gradient to carry cobbles and boul- 
 ders ; and, even in the Buena Vista area, there was a 
 relief of several hundred feet at the beginning of pre- 
 lone Eocene ( ?) sedimentation. 
 
 At the beginning of lone time conditions changed in 
 such a way that the sediments carried to the foot of the 
 mountains became highly weathered. In discussing the 
 reason for the change MacGinitie ^'' presented evidence 
 to show that the weathering took place during transporta- 
 tion and suggested that a rise in base level may have been 
 the main cause. However, the evidence presented earlier 
 in this paper concerning the development of the laterite 
 and its relation to the sediments of the pre-Ione Eocene 
 ( ?) and lower lone suggests that there was a change to a 
 more tropical climate after pre-Ione Eocene ( ?) time. 
 
 Deposition of the lone-type sediments continued with 
 minor interruptions until the major period of erosion 
 that closed lone time. Upper lone sediments do not show 
 as great a degree of weathering as do lower lone sediments. 
 This may have been due to a change to more temperate 
 climate or to a change in the conditions of erosion. 
 
 During the Tertiary the Sierra Nevada began to rise 
 and as a result the gradient of the southwestward flowing 
 rivers was increased. The first slight Tertiary uplift of 
 the Sierra Nevada may have come at the end of lone 
 time. Valley Springs <leposition began with the eruption 
 of rhyolite in the higher parts of Sierra Nevada. At the 
 close of the rhyolite period, or possibly simultaneously 
 with the last of the rhyolite eruptions, andesitic eruptions 
 began in the east which resulted in a series of mud flows 
 down the west slope of the mountains. The Buena Vista 
 area was flooded with andesite breccia and conglomerate 
 until the surface reached an elevation of about 800 feet.'*" 
 
 *« TaUaferro, N. L., op. cit., p. 285. 
 
 '*■'• MacGinitie, H. D., op. cit., pp. 17, 25-2G. 
 
 *> Piper, A. M., op. cit., pi. 4. 
 
 '.^■tfS0^l^ 
 
 Fku'RK in. Buena Vi.sta I?uttes. ForeRround i.s flat top of mesa 
 
 held up l)y hard conglomerate in A'alley Springs formation. Camera 
 
 bearing east. 
 
 The present drainage pattern of the Sierra Nevada 
 began to evolve in late (?) Miocene or possibly early 
 Pliocene time with the cessation of the andesite mud flows 
 and the initiation of consequent .stream patterns on the 
 Mehrten surface.**^ The land forms of the Buena Vista 
 area were the result of the late Pleistocene dissection of 
 part of the Arroyo Seco pediment. Erosion was acceler- 
 ated during these periods by further elevation of the 
 mountains. Lindgren ''^''* and Matthes *^ said that the major 
 elevation of the Sierra Nevada took place in the Pleisto- 
 cene, and estimated that the elevation of the crest of the 
 range was increased by 6000 feet at that time. 
 
 ECONOMIC GEOLOGY 
 Clay 
 
 The present production of clay in the area is limited to 
 a deposit of the lone sand with a low iron content for use 
 in the manufacture of white portland cement. Clay depos- 
 its occur in the area, however, that would furnish raw 
 material for the manufacture of refractories and white- 
 wares and for use as fillers in rubber and paper. Because 
 there is a critical need for clays with high deformation 
 temperatures for the manufacture of refractories, the in- 
 vestigation of deformation temperatures was emphasized 
 in the study of the clays in the area. 
 
 Technical Data on Refractor;/ Clays. Pyrometric cone 
 ecjuivalent (P. C. E.) is used as a measure of refractori- 
 ness of clays and fireclay refractories. The indu.stry ad- 
 heres to the following classification for fireclay brick on 
 the basis of refractoriness: 
 
 sujier duty — ecpial to or more than I'.C.E. .'53, 
 greater than ]74."i° (". or .S17."?° F. .-it a temperature increase of lOO" 
 (". per hour. 
 
 high heat dut.\ — r.C.F. .••.l-:'.2, 
 greiiter than 1()!S()° ('. or .'iOriCi" F. at a temperature increase of 100° 
 V. per hour. 
 
 medium heat duty — I'.C.K. 2!)-.'!0, 
 greater than 16-40° ('. or 2!)S4° F. at a temperature increase of 100° 
 C. per hour. 
 
 low heat duty— I'.C.K. 1!)-2S, 
 greater tiian l.Tl.-t" t". or 27r(!)° F. at .-i tenii>erature increase of 100° 
 ('. i)er hour. 
 
 •■■ Ibifl., pp. 24-25. 
 
 >* Lindpren, Waldemar, The Tertiary gravels of the Sierra Nevada of 
 
 California: U. .S. C.eol. Survey Prof. Paper 73, pp. 46-48, 1911. 
 ^'■' Matthes, F. E., Geologic history of the Yosemite Valley : U. S. Geol. 
 
 Survey Prof. Paper 160, pp. 43-44, 1930. 
 
loNE Formation, Cuena Vista Area 23 
 
 _, nn c< Li. ■ 1 c u ■ c in rv 1 f Type III no examples 
 
 Figure 20. South side of mesa shown in figure 10. Overhang of 
 
 hard conglomerate caused by erosion of soft clay and sandstone Reflectance of ^0%-(M% for green filter 
 
 below. Type I 20-28 
 
 Type II l,j-2,S 
 
 '/ ' "j. j^^^^Mti ''•^'**' ^^^ ■^■'^"■^ 
 
 i^^^^^K/^i Keflectance of 0%-80% for green filter 
 
 ''* J^^^^^BF rj^jjip^ J II III ^J9 
 
 * In general, the high reflectance values correspond to white or very 
 light tints or shades, usually of cream, buff, tan, and pink ; the 
 lower values to deeper colors. 
 
 A more specific' classififation is not possible \\\\\\ tlie 
 
 fe^^-j-!^^?*'** ■ ' ^^?^'^^!?F'^H^^tBtt3|^^B present available knoAvled<re of the structure and composi- 
 
 ^^B^^^^'-KA ~^^p^^ . ^S^^SI^^^H tion of the days. The marked dependence of refractoriness 
 
 '^^E^**' - ^v crdSJoS ^^r^ .^>>^j^BEs!y^m '*•! color is due to the fact that the iron oxide responsible 
 
 ^ - x^' "^^I^^ ' '*' ^' ^wRSB^^KS^^t^il^^^^^^^^^^ ^"^ *'^^ color is also a flux, an especially strong one if pres- 
 
 ^^i.-.^' • ^^r^'^^^^^^^^^B^Bp^^fe ent in the form of ferrous compounds. 
 
 ■f- \ ^^ S^^^^BP^W ^^^ important conclusion is that the only clays suitable 
 
 * / v^HbBrtv" F^ f*"" super duty are kaolinites with unmodified or halloy- 
 
 ^,/ * '-f i^fl^ff^ •• ■^' 1 ^ site-tendinp: Tyjie I curves and with fired color (1000° 
 
 l^--.^;-,' - ' •^"JAg|BB %'> /y ■■''■y^ C) reflectance values *rreater tlian 60 percent for preen 
 
 %j"j,*»- v ' - . . ,, ^nEK^jyy^^S filter as measured with a reflectometer tvpe of instrument. 
 
 „ „, ^ , ^. „, ,,.,, , ,, ,, Vlnu Pr()<h(ction. Four clay pits are in the area. 
 
 Figure 21. Terrace gravel resting on Cheney IIill day in old gold- _, •', ,,, w i ti i i t^ i- t:i -x 
 
 placer workings about 1000 feet northeast of Buena Vista. Camera ^hree, the ^Voolford, Rancher, and Kaohn-Fye pits, are 
 
 iicMririf; cist. ill the Upper lentil of the lower lone member, and the other, 
 
 the Chitwood pit. is in the Chitwood clay of the upper 
 
 ^.^ ■^r^ ' > ' V^^H ^one member. The Fancher pit has been described by Die- 
 
 ^* a'uJ- - t'^^B trich "" for the period duriiifr which it was operated by AV. 
 
 a',^ S. Dickey Clay Manufacturiiifr Company. I'ntil 1927 the 
 
 s operations were entirely open pit but in that year tunnel- 
 
 y ^ '^P'j^^^^i^Kk jli* '"f^ "^^'^^ started in order to get under a thick overburden. 
 
 — • _^ MT. * ' "HBBII^kH^ ^''^ ''^^^ production was from Cheney Tlill clay Avhich had 
 
 V r}X . if' HHR^HS a P.C.E. of :iS to;}4.°i The Woolfordpit isalsoin Cheney 
 
 * '\ NC^ '^aBfe'^^ Hill clay. At the Woolford locality the Cheney Hill clay 
 
 \ ' . ' ^'SC!^"- has a P.C.E. of 31 to 33."- The Kaolin-Fye pit is operated 
 
 ^ • ' 'sSL^s^JM^ by the Calaveras Cement Company and supplies a mixture 
 
 p^.^ ■ of nearly iron-free clay and quartz sand for the manufac- 
 
 .^^^^^^—^^ ^^"^-^ ■• ture of white Portland cement. Work on the pit was first 
 
 *]^ ^f^^^^^^j^^3r-^'' — ~~ ~~ begun in January 1050. The Chitwood pit Avas worked as a 
 
 "'^ ' J source of tlie upper Tone Chitwood clay. The clay is very 
 
 sandy and has a P.C.E. of 30 to 31.»^ 
 
 ™ Dietrich, "W. F., The clay resources and the ceramic industry of 
 (California: California Div. Mines and Mining Bull. 99, pp. 58-59, 
 1928. 
 
 »' Ibid., p. 280. 
 
 Figure 22. Channel cut into upper lone brown sandstone, filled „, ihid*^"' ^' ' " °"' "^" ^' '*' 
 
 ■with terrace gravel. East face of Fancher pit. oa Ibid! 
 
24 
 
 Special Report 19 
 
 Figure 23. 
 
 Old guld-placer workings in alluviui; 
 Fancher pit. Camera bearing east. 
 
 jusL east of 
 
 Table 2. Differeniial ihermal analysis, pyrometric cone equwalent, 
 
 and fired color for samples of clay from the Buena Vista area 
 
 and of commercial clays from near the town of lone. 
 
 
 
 
 
 Photometer data 
 
 
 
 
 
 (Clay calcined to 
 
 
 
 
 
 
 1,000° C.) 
 
 
 
 
 D.T.A. 
 
 
 Filter color 
 
 Hole no. 
 
 Depth 
 
 type 
 
 P.C.E. 
 
 
 
 
 
 Green 
 
 Amber 
 
 Blue 
 
 18-1 
 
 126' -129' 
 
 la 
 
 31 + 
 
 70.5 
 
 76.0 
 
 55.0 
 
 
 132' -138' 
 
 I-VIa 
 
 33 H 
 
 77.0 
 
 82.0 
 
 62.5 
 
 
 139' -143' 
 
 II 
 
 31 + 
 
 72.0 
 
 77.0 
 
 56.0 
 
 
 149' -151' 
 
 Ila 
 
 23 
 
 70.5 
 
 74.5 
 
 52.5 
 
 
 155' -155 '7" 
 
 I 
 
 33 
 
 81.0 
 
 85.0 
 
 66.0 
 
 
 l??'^ 
 
 II>Ia 
 
 33— 
 
 65.5 
 
 75.0 
 
 
 
 192' -193 '6' 
 
 II 
 
 20-23 
 
 39.0 
 
 48.0 
 
 31.5 
 
 
 217' -229' 
 
 la 
 
 31H 
 
 75.0 
 
 79.5 
 
 62.0 
 
 
 242'3''-246' 
 
 II 
 
 31H 
 
 77.0 
 
 83.0 
 
 64.0 
 
 
 250' 
 
 II 
 
 26 
 
 34.5 
 
 51.0 
 
 
 
 265'9''-269' 
 
 Ir 
 
 26 
 
 51.0 
 
 58.0 
 
 '"'42!5' 
 
 
 324' -325' 
 
 III 
 
 19— 
 
 47.0 
 
 55.0 
 
 35.5 
 
 
 326' -329' 
 
 III 
 
 19 + 
 
 48.5 
 
 56.5 
 
 36.5 
 
 
 329' -334' 
 
 III 
 
 18H 
 
 51.5 
 
 60.0 
 
 35.0 
 
 
 334' -338' 
 
 III 
 
 18H 
 
 49.5 
 
 58.0 
 
 32.0 
 
 
 366' 
 
 III 
 
 16 
 
 43.0 
 
 55.5 
 
 
 18-2 
 
 69' 
 
 II 
 
 31— 
 
 73.0 
 
 78.5 
 
 
 
 83' 
 
 II 
 
 31— 
 
 70.0 
 
 75.5 
 
 
 
 100' 
 
 Ilr 
 
 23 
 
 69.0 
 
 73.0 
 
 
 
 159' 
 
 Ir 
 
 31 — 
 
 83.0 
 
 86.5 
 
 
 
 225' 
 
 Ia->II 
 
 26 
 
 47.0 
 
 61.0 
 
 
 
 253' 
 
 IIa->-III 
 
 20 + 
 
 48.0 
 
 60.5 
 
 "27.0 
 
 18-3 
 
 168' 
 
 II->-Ia 
 
 28 
 
 61.0 
 
 70.0 
 
 46.0 
 
 
 216' 
 
 la 
 
 26 
 
 66.0 
 
 75.0 
 
 46.0 
 
 
 256' 
 
 ? (carbon) 
 
 14!3 
 
 21.5 
 
 31.0 
 
 11.5 
 
 
 274' -277 '4" 
 
 III 
 
 23— 
 
 50.5 
 
 65.5 
 
 24.5 
 
 
 287' 
 
 III 
 
 16 
 
 40.0 
 
 52.0 
 
 18.0 
 
 24-2 
 
 164 '6" 
 
 Ih 
 
 31H 
 
 67.5 
 
 76.0 
 
 56.0 
 
 24-3 
 
 36 '6" 
 
 III>IIIb 
 
 15H 
 
 49.0 
 
 60.0 
 
 24.0 
 
 
 103' 
 
 III 
 
 19 
 
 54.0 
 
 61.0 
 
 35.5 
 
 
 125 '6' 
 
 Ih 
 
 33 + 
 
 69.0 
 
 74.0 
 
 58.0 
 
 
 137' 
 
 Ih 
 
 34 + 
 
 72.0 
 
 77.5 
 
 62.0 
 
 
 202' 
 
 Ih 
 
 17 + 
 
 19.0 
 
 28.0 
 
 7.0 
 
 13-1 
 
 289' 
 
 I 
 
 23— 
 
 31.0 
 
 39.5 
 
 23.0 
 
 
 304' 
 
 Ila 
 
 14 
 
 18.0 
 
 25.0 
 
 9.0 
 
 7-1 
 
 40' 
 
 II 
 
 33— 
 
 74.0 
 
 79.0 
 
 
 
 57' 
 
 I 
 
 33 
 
 81.0 
 
 84.5 
 
 
 
 82 '6" 
 
 Ir 
 
 26 
 
 47.5 
 
 63.0 
 
 
 
 169' 
 
 Ir 
 
 26 
 
 80.5 
 
 84.0 
 
 
 
 221' 
 
 II->-Ia 
 
 15 
 
 40.0 
 
 48.5 
 
 
 No. 1* 
 
 
 Ih 
 I->-Ia 
 
 33— 
 31^ 
 34 
 33 
 
 81.0 
 74.0 
 
 85.0 
 79.5 
 
 
 No. 2* 
 
 
 
 No. 3* 
 
 
 Ih 
 I->-Ia 
 
 77.5 
 74.5 
 
 81.5 
 80.0 
 
 
 No. 4* 
 
 
 
 No. 5* 
 
 
 Ir 
 
 30H 
 34 + 
 
 83.5 
 
 86.5 
 
 
 No. 6* 
 
 
 I 
 
 70.0 
 
 77.0 
 
 
 No. 7* 
 
 
 Ih 
 Ilr 
 II>Ia 
 
 34 
 30 
 20 
 
 63.0 
 82.5 
 29.5 
 
 73.0 
 86.0 
 46.5 
 
 
 No. 8* 
 
 
 
 No. 9* 
 
 
 
 * Samples no. 1 to no. 9 are typical commercial clays from the lower lone member in the 
 vicinity of the town of lone. 
 
 No Edwin clay has been mined in the area, but the 
 p:eolo^ic mapping and the study of the drill cores re- 
 vealed the presence of Edwin clay at the surface and 
 at depth along both sides of the greenstone ridge south 
 of Jackson Creek. In every place where the Edwin clay 
 is found, it rests directly on sedimentary laterite. The 
 largest outcrop area of Edwin clay is in a stream bed 
 immediately east of the large greenstone outcrop south 
 of Jackson Valley. 
 
 Other Minerals 
 
 Lignite, gold, and building stone have been produced 
 in the area in the past. Lignite was mined from the 
 middle member of the lower lone for many years at the 
 Buena Vista coal mine, about a mile south of Buena 
 Vista.*** The American Lignite Products Company is 
 operating a plant at the location of the Buena Vista coal 
 mine for the extraction of Montan wax from lignite. The 
 plant started operations with raw material from the same 
 area but now uses lignite from near lone. Gold was dis- 
 covered in the area in 1854 or 1855,"^ and in 1856 a 15- 
 mile ditch was built to supply water for placer mining. 
 These operations continued until at least 1880 ^"^ and 
 covered most of the slopes and gulches that are below 
 deposits of terrace gravel. The latest gold production 
 was from dredge operations in the upper end of Jackson 
 Valley. 
 
 Stone was quarried from the hard sandstone member 
 of the upper lone, probably for local construction of 
 buildings and fences. The quarries still in evidence are 
 at the tops of Chitwood Hill and the hill 3000 feet east 
 of Woolford pit, and on the side of Buena Vista Peak. 
 Hard rhyolite tuff at the top of Buena Vista Peak has 
 also been quarried. 
 
 VALUE OF CERAMIC TESTS IN GEOLOGIC 
 INVESTIGATION 
 
 Each of the ceramic techniques employed in this study 
 was valuable in helping to interpret the geology and 
 mineralogy of the area and to indicate the economic 
 value of the clays. It is apparent that these techniques 
 would have many applications in other geologic studies 
 as well as in the search for clays u.seful in industry. 
 
 Clay mineralogy is complicated by the numerous pos- 
 sible isomorphous substitutions and, for that reason, a 
 breakdown of the kaolinite group minerals into a number 
 of types, as presented here, would be extremely difficult 
 based only on microscopic and X-ray diffraction analyses. 
 In contrast, the interpretation of a series of differential 
 thermal curves was relatively simple. It is therefore a 
 powerful aid in indicating the presence of minor varia- 
 tions in structure. Differential thermal analyses aid 
 greatly in the identification and determination of forma- 
 tions and strata and in correlating them from hole to 
 hole. The determination of the type of clay resulting 
 from the weathering of certain rock types provides valu- 
 able information for the interpretation of geologic his- 
 
 B< Tucker, W. B., Amador County: California Min. Bur. Kept. 14, 
 
 Logan, 'r.' a!*,' Auburn field division — Amador County : California Min. 
 
 Bur. Kept. 17, p. 413, 1921. , ^ x ^,w 
 
 Loean C A , .Sacramento field division — Amador County : California 
 
 Min. Bur. Kept. 23, pp. 146-147, ];t27. 
 Allen, V. T., op. cit., pp. 408-409. 
 Piper, A. M., op. cit., pp. 82-S'?. 
 »'■ Mason, J. D., op. cit., p. 2fi5. , ,,. . ^ 
 
 w Stretch, R. H., A report on the Amador Canal and Mining Companj, 
 p. 27, San Francisco, 1880. 
 
JONE FOKMATIOX, BUENA ViSTA AkEA 
 
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26 
 
 Special Report 19 
 
 tory. The fact that Type I kaolinitic clay resiilts from the 
 weathering of greenstone and Types II and III kaolinitic 
 clays are a product of the weathering of Alariposa slate is 
 indicative of sources of sedimentary clays of these types. 
 It is of economic value to know that only clays of Type I, 
 with very light shades of color (approaching white) are 
 known sources of super duty clays. It is therefore indi- 
 cated that the lower lone member is probably the only 
 commercial source of super duty clays in the Buena 
 Vista area. 
 
 An indirect value of the differentiTil thermal analyzer 
 is the relative simplicity of the apparatus and the ease 
 with which curves can be obtained by untrained opera- 
 tors, in contrast with the amount of training necessary to 
 undertake petrographic and X-ray diffraction analyses 
 and the time required for P.C.E. determinations. 
 
 It is hoped that the paper has shown the value of 
 ceramic tests in the interpretation of geology, and that 
 they should be considered as an aid in geologic studies, 
 particularly of sedimentary areas. 
 
 SELECTED BIBLIOGRAPHY 
 
 Allen, V. T., The lone formation of California : Univ. California, 
 
 Dept. Geol. Soi., Bull., vol. 18, pp. :?47-448, 1029. 
 Bates, T. F., Origin of the Edwin clay, lone, California : Geol. Soc. 
 
 America Bull., vol. 56, pp. 1-H8, 104."(. 
 Bradley, W. F., The structural scheme of attapulgite: Am. Min- 
 eralogist, vol. 28, p. 1, 1!)4.'?. 
 Brindley, G. W. (editor), X-ray identification and crystal structures 
 
 of clay minerals : The Mineralogical Society (Clay Mineral Gronj)), 
 
 34.J pp., liondon, ID.jl. 
 Clark, B. L., The stratigraphy and faunal relationships of the 
 
 Meganos group, middle Kocene of California : Jour. Geology, vol. 
 
 29, pp. 12."., 161-16.-), 1921 . 
 Clark, B. L., and Yokes, H. E., Summary of the marine Eocene 
 
 sequence of AVestern Xorth America : (Jeol. Soc. America Bull., 
 
 vol. 47, pp. 8.-.1-878. 1936. 
 Dickerson, I{. E., Fauna of the ?]ocene at ^larysville Bnttes, Cali- 
 fornia : I'niv. California, Dept. (Jeol. Sci., Bull., vol. 7, pi). 2.->7- 
 
 298, 19i;?. 
 Dickerson, R. E., Stratiurai)liy and fauna <if tlie Tejon P^ocene of 
 
 California : I'niv. California, Dept. (Jeol. Sci., Bull., vol. 9, ji]). 
 
 .387-417, 1916. 
 Dietrich, W. F., The clay resources and the ceramic industry of 
 
 California : California Div. Mines and Mining Bull. 99, j.p. 58-,^, 
 
 280, 1928. 
 Edelman, C. H.. and Favejee, .T. Ch. T-., On the crystal structure of 
 
 montmorillonite and halloysite : Zeitschr. Kristallographie, band 
 
 102, pp. 417-4.31, 1940. 
 Grim, R. E., Modern concepts of clay materials : .Tour. (Jeology, vol. 
 
 50, pp. 22.-.-27.->, 1942. 
 Grim, R. E., Bray, R. II.. and Bradley, W. F., The mica in argillace- 
 ous setliments : Am. Mineralogist, vol. 22, pp. 813-829, 1937. 
 Gruner, .1. W., The crystal structure of kaolinite : Zeitschr. Kristal- 
 
 lographie, hand 8.">, pp. 7.')-88, 1932. 
 Hendricks, S. B., Concerning the crystal structure of kaolinite 
 
 Al-'O-v2SiO::-2H-0 and the composition of anau.xite : Zeitschr. 
 
 Krystallographie, hand O.j, p. 247, 19.36. 
 Hendricks, S. B., On the crystal structure of the clay minerals: 
 
 dickite, halloysite, and hydrated halloysite: .Jour. Miueralog. Soc. 
 
 America, vol. 23, pp. 29.-)-.301, 1938. 
 Hendricks, S. B., The crystal structure of nacrite Al-On-2SiO-'-2H-.;0 
 and the polymorphism of the kaolin minerals: Zeitschr. Kristal- 
 lographie, hand 100, pp. 509-.-.18, 19.39. 
 
 Hoffman, V., Endell, K.. and AVilm, D., Kristallstruktur und quellung 
 von montmorillouit (Crystal structure and swelling of montmoril- 
 lonite) : Zeitschr. Kristallographie, l)and 86, pp. 340-348, 193.3. 
 
 Jenkins, O. P., (Jeologic map of California : California Div. Mines, 
 scale 1 : .-.00,000, 6 sheets, 1938. 
 
 Jenkins, O. I'., (Jeology of i.lacer deposits, in Averill, C. V., Placer 
 mining for g<dd in California: California Div. Mines Bull. 13.5, 
 2nd ed., fig. 64, p. 176, 1950. 
 
 Krumhein, AV. C., and Sloss, L. L.. Stratigraphy and sedimentation, 
 pp. 150-151, San Francisco, AV. H. Freeman and Company, 1951. 
 
 Lindgren, AA'aldemar, V. S. Geol. Survey (Jeol. Atlas, Sacramento 
 folio (no. 5), p. 3, 1894. 
 
 Lindgren, AValdemar, The Tertiary gravels of the Sierra Nevada of 
 California : F. S. (Jeol. Survey Prof. I'aper 73, pp. 21-28, 46-48, 
 196-197, pi. 1, 1911. 
 
 Logan, C. A., Auburn field division — Amador County : California 
 Min. Bur. Rept. 17, p. 413, 1921. 
 
 Logan, C. A., Sacramento field division — Amador Countv : California 
 Min. Bur. Rept. 23, pp. 146-147, 1927. 
 
 MacGinitie, H. D., A middle Eocene flora from the central Sierra 
 Nevada : Carnegie Inst. AVashington I'uh. .534, 167 pp., 1941. 
 
 Manual of A. S. T. AI. standards on refractory materials: Am. Soc. 
 Testing Alaterials, j.p. 69-72, 1948. 
 
 Alarshall, C. E., Soil science and mineralogy : Soil Sci. "Soc. America 
 Jour., vol. 1, pp. 23-31, 1937. 
 
 Marshall. C. E., The colloid chemistry of the silicate minerals, p. 14, 
 Academic I'ress, 1!)49. 
 
 Mason, .T. D., History of Amador County, California, pp. 125-1.36, 
 189, 242-2.50, 265, Oakland, Thompson and AA'est, 1881. 
 
 Matthes. F. E., (Jeologic history of the A'osemite A'alley : U. S. Geol. 
 Survey I'rof. I'aper 160, pp. 43-44, 1930. 
 
 Pask. .1. A., and Davies, Ben. Thermal analysis of clay minerals and 
 acid extraction of alumina from clays: U. S. Bur. ]\Iines Rept. 
 Inv. 37.37, 2S pp., 1943. 
 
 Piper. A. M., (Jale, II. S., Thomas II. E., and Rol.in.sou, T. AV., 
 (Jeology and ground-water hydrology of the Mokelumne area, Cali- 
 fornia : V. S. Geol. Survev AVater-Supplv I'aper 780, 230 pp., 
 19.39. 
 
 Speil, Sidney, Berkelliamer, L. H.. I'ask, .7. A., and Davies, Ben, 
 I>ifferential thermal analysi.s — its application to clays and other 
 aluminous minerals: I'. S. Bur. Alines Tech. Paper 664, 81 pp., 
 1945. 
 
 Spragne, Malcolm, Climate of California, in Climate and man : V. S. 
 Dept. Agr. Yearbook 1941, pp. 793-795, 1941. 
 
 Stearnes, H. T., Robinson, T. AY., and Taylor, G. H., Geology and 
 water resources of the Mokelumne area, California: U. S. Geol. 
 Survey AYater-Supply I'aper 619, 402 pp., 19.30. 
 
 Stewart, Ralj.h, Lower Tertiary stratigraphy of Mount Diablo, 
 Marysville Buttes, and west border of Lower Central A'alley of 
 California : V. S. Geol. Survey Oil and Gas Prelim. Chart 34, 
 Sheet 2, 1949. 
 
 Stretch, R. IL, A rej.ort on the Amador Canal .-iiid Mining Company, 
 p. 27, San Francisco, 1880. 
 
 Taliaferro, N. li., Alanganese deposits of the Sierra Nevada, their 
 genesis and metamorphism : California Div. Mines Bull. 125, pp. 
 2W-28(i, 306.307, 1943. 
 
 Tucker. AA'. B., Amador Countv : California Min. Bur. Rept. 14, p. 
 11, 191.5. 
 
 Turner, H. AY., The rocks of the Sierra Nevada : I'. S. (Jeol. Survey 
 14th Ann. Rept., pt. 2, p. 485, 1894. 
 
 Turner, H. AY., V. S. Geo]. Survey Geol. Atlas, .lackson folio (no. 11), 
 1894. 
 
 Turner, II. AV., Further contributions to the geology of the Sierra 
 Nevada : V . S. CJeol. Survey 17th Ann. Rept., pt. 1, p. 721, 1896. 
 
loNE Formation, Buena Vista Area 
 
 APPENDIX 
 
 Record of drill holes in the Buena Vista area. 
 
 HOLE 7-1 
 
 220 feel S of Rinyer norlh property line, <!,!0 feet E of Ringer next 
 property line; IG.'iO feet ^^"S^\' of liuena Vistn. Elevation 309 feet. 
 
 27 
 
 No core 
 
 Thickness 
 feet inches 
 - '.',0 
 
 Eocene lone formation 
 Lower lone member 
 
 Krown lignite containing much clay 
 
 BiifF yellow-stained clay 
 
 I'ale brown, yellow-stained clay 
 
 Light cream-colored clay 
 
 Dark-gray carbonaceous clay 
 
 Lignite 
 
 Dark-gray carbonaceous clay 
 
 Oray-brown clay 
 
 IJgnite 
 
 Krown clay 
 
 White clay 
 
 White clay ; some sand grains 
 
 White sandy clay 
 
 lyight-gray sandstone and some c-lay 
 Conglomerate ; weathered to buff 
 
 color 
 
 White argillaceous sandstone con- 
 taining iron nodules 
 
 Buff sandstone ; very abundant iron 
 
 nodules 
 
 Light-buff coarse-grained sandstone. 
 Huff argillaceous fine-grained san<l- 
 
 stone 
 
 Ruff argillaceous medium-grained 
 
 sandstone 
 
 Coarse-grained sandstone containing 
 
 some clay ; iron-oxide cement 
 
 Fine-grained white, argillaceous 
 
 sandstone, some red stains 
 
 Huff clay 
 
 Huff conglomerate 
 
 Reddish-buff clay 
 
 Yellow-brown clay 
 
 Conglomerate 
 
 Dark gray carbonaceous clay 
 
 Very light-buff clay, some silty i)art- 
 
 ings, some carbonaceous streaks.. 
 
 Purplish clay 
 
 Very dark-gray clay containing lig- 
 nite seams 
 
 Very dark-gray sandy clay 
 
 Conglomeratic sandstone ; dark gray, 
 
 grading to light-brown 
 
 No core. (One piece of white <-lay) _ 
 Fine-grained white argillaceous 
 
 sandstone 
 
 Gray-white sandstone with clay 
 
 cement 
 
 Conglomeratic gray-white sandstone 
 
 with clay cement 
 
 Red and buff clay and pebbles 
 
 (Jray-white conglomeratic sandstone 
 Lignite 
 
 4 
 
 
 
 
 r» 
 
 7 
 
 7 
 
 ;» 
 
 r. 
 
 1 
 
 1 
 
 
 
 (5 
 
 4 
 
 
 1 
 
 1 
 
 1 
 
 11 
 
 
 
 (i 
 
 1 
 
 4 
 
 
 
 S 
 
 1 
 
 4 
 
 
 
 1) 
 
 3 
 
 4 
 
 •> 
 
 11 
 
 10 
 4 
 3 
 4 
 3 
 
 4 
 
 
 
 1 
 
 
 7 
 10 
 
 3 
 
 1 
 
 
 1 
 1 
 
 
 Depth 
 feet inches 
 30 
 
 34 
 
 
 34 
 
 5 
 
 42 
 
 
 4.-, 
 
 ." 
 
 4<; 
 
 
 
 47 
 
 
 r,i 
 
 
 52 
 
 1 
 
 54 
 
 
 54 
 
 
 
 (iO 
 
 .s 
 
 (>2 
 
 
 02 
 
 8 
 
 04 
 
 
 04 
 
 i) 
 
 (MS 
 
 1 
 
 71 
 
 
 73 
 
 
 74 
 
 81 
 
 S4 
 04 
 OS 
 101 
 105 
 10S 
 110 
 
 114 
 115 
 
 lie. 
 
 117 
 
 124 
 
 134 
 
 137 
 
 138 
 
 139 
 140 
 142 
 142 
 
 n 
 
 11 
 
 Thickness 
 feet inches 
 
 Fine-grained gray-white argillaceous 
 
 sjindstone 
 
 Dark gray carbonaceous sandy clay_ 
 Cray-white silty clay containing 
 
 pebbles 
 
 Fine-grained gray carbonaceous 
 
 sandstone 3 
 
 Dark-gray, carbonaceous, argilla- 
 ceous, medium-grained sandstone. 
 
 White clay: some silt 7 
 
 Conglomeratic white clay; some silt 
 Fine-grained, white, argillaceous 
 
 sandstone 15 
 
 (Jray carbonaceous clay 
 
 Sandy lignite 1 
 
 Carbonaceous sandy clay 
 
 Argilljiceous lignite 
 
 Carbonaceous clay 
 
 Argillaceous lignite 
 
 Cray carbonaceous sandy clay 10 
 
 Light-brown clay 1 
 
 Highly carbonaceous clay ',', 
 
 Dark-gray carbonaceous clay, saudy 
 
 lenses 4 
 
 Huff silty clay 
 
 (Jray cjirbonaceous clay 1 
 
 Huff silty clay ; iron nodules 3 
 
 Huff silty clay 
 
 Light -l)uff and red mottled sandy 
 
 clay 2 
 
 Red sandy clay, some buff mottling. 7 
 
 Red an<l buff mottled clay 2 
 
 Huff clay 1 
 
 Eocene (?) unnamed pre-lone beds 
 
 Cray argillaceous siltstone 4 
 
 Dark-gray carbonaceous argillaceous 
 
 siltstone , 
 
 Very light-brown argillaceous silt- 
 stone 
 
 liight-brown argillaceous siltstone ._ 1 
 Cray carbonaceous argillaceous silt- 
 stone (5 
 
 Dark-gray carbonaceous argilla- 
 ceous siltstone 12 
 
 Dark-gray carbonaceous conglomer- 
 atic line-graine<l sandstone 3 
 
 Quartz pebbles in greenish clay 
 
 matrix 
 
 Jurassic Amador group 
 
 Green day containing some lighter 
 
 colored areas 2 
 
 Highly altered greenstone 5 
 
 Fresh greenstone 2 
 
 (Jreenstone, partially altered to 
 
 clay 2 
 
 Fresh greenstone 1 
 
 Depth 
 feet inrhes 
 
 143 
 
 143 G 
 
 144 
 
 147 
 
 
 
 147 
 
 G 
 
 (i 
 
 155 
 104 
 
 170 
 1S5 
 
 ISO 
 
 
 
 3 
 
 ISO 
 1S7 
 
 9 
 
 !) 
 
 1S7 
 
 9 
 
 I! 
 
 ISS 
 
 
 
 204 
 
 
 5 
 
 205 
 
 5 
 
 7 
 
 200 
 
 
 
 
 
 21:: 
 
 214 
 215 
 
 G 
 
 
 
 21S 
 210 
 
 221 
 
 22S 
 
 9 
 
 *) 
 
 230 
 
 o 
 
 1 
 
 2:u 
 
 •• 
 
 
 235 
 
 3 
 
 
 
 235 
 
 9 
 
 G 
 
 23G 
 237 
 
 
 
 G 
 
 244 
 25G 
 2.59 
 
 
 G 
 
 2.59 
 
 6 
 
 
 
 2G2 
 
 
 207 
 
 3 
 
 2(i9 
 
 o 
 
 271 
 
 7 
 
 273 
 
28 
 
 Special Eeport 19 
 
 HOLE 13-1 
 
 20 feet E of Fancher trest property line, 110 feet N of Faiirher south 
 property line. Elexmtion 2JiJi feet. 
 
 Thickne.ts Depth 
 
 feet inches feet inches 
 
 Xo core 236 236 
 
 Eocene lone formation 
 Lower lone member 
 
 Ferruginous nodule 1 237 
 
 Yellow-stained clay 9 237 
 
 White clay 2 6 240 3 
 
 White sandy clay « 240 9 
 
 White clay 1 3 242 
 
 White, yellow-stained clay 1 5 243 5 
 
 White sandy clay ; yellow stain (> 243 11 
 
 White clay 1 244 
 
 White argillaceous sandstone ; yel- 
 low stain 1 24r> 
 
 White clay 3 24.". 
 
 Light gray clay 8 6 253 ' 9 
 
 I'ebbles, 2 inches in niaxiinum di- 
 ameter 3 2.'»4 
 
 Fine-grained cream colored sand- 
 stone 20 274 
 
 Light-gray silty clay 1 275 6 
 
 Ivight-gray silty clay ; iron nodules _ 8 6 2S4 
 
 White clay ; iron nodules 10 294 
 
 Eocene (?) unnamed pre-lone beds 
 Green silty clay ; iron nodules 
 
 (siderite) ^ 10 304 
 
 Gray-green silty clay ; siderite 
 
 nodules 9 313 
 
 Buff clay 1 314 
 
 HOLE 13-2 
 
 200 feet S. of county road, 30 feet "IT. of Fancher cast property 
 line. Elevation 2.jf) feet. 
 
 Thickness Depth 
 
 Quaternary alluvium (?) feet inches feet inches 
 
 Sand, gravel, and clay * 49 49 
 
 Eocene lone formation 
 Lower lone member 
 
 Lignite * -! 1 50 
 
 Sand, gravel, and clay * 40 90 
 
 Lignite* 17 107 
 
 Clay, sand, and gravel * 55 162 
 
 White medium-grained sandstone; 
 
 some clay 2 164 
 
 White medium-grained sandstone; 
 
 iron no<lnles and clay 1 165 
 
 Yellow to red sandy clay 3 168 
 
 Buff to red clay with a little sand 3 171 
 
 White sandy clay heavily stained 
 
 with red and yellow 12 172 2 
 
 Mottled red and yellow sandy clay 10 17.*'. 
 
 White clay 6 173 6 
 
 Reddish sandy clay 1 6 175 
 
 White sandy clay 9 175 9 
 
 I'ink and dark-red clay :'. 176 
 
 IMnk-stained sandy white clay 6 176 6 
 
 Coarse, very angular quartz grains 
 
 cemented with red iron compound 6 177 
 
 Thi 
 feet 
 
 AVhite clay M'ith red stains 7 
 
 Red and yellow banded clay 1 
 
 White clay 3 
 
 I^ight-brown clay 
 
 I>ight-l)rown fine sandy clay with 
 
 reddish streaks 1 
 
 liight-brown argillaceous sandstone. 
 Light-brown clay with some silt and 
 
 fine sand grains 1 
 
 Brownish-gray clay 4 
 
 Gray clay with scattered sand grains 2 
 
 Brownish-gray sandy clay 1 
 
 Medium-gray clay with some sand 
 
 grains; carbonaceous 2 
 
 Light-gray clay with some sand 
 
 grains 1 
 
 Gray clay 2 
 
 IMedium-gray clay with pieces of car- 
 bonaceous material 2 
 
 Tiight-gray clay 3 
 
 Sandy clay and silt ranging in color 
 
 from gray to l)lack * 51 
 
 Gray medium-grained sandstone; 
 
 yellow stain 10 
 
 Sandy clay and silt ranging in color 
 
 from gray to black * 26 
 
 Sandy red clay * 3 
 
 Deep-red conglomeratic material 
 
 with white fragments 2 
 
 Rnst-brown clay containing a few 
 
 pel)bles 2 
 
 AVhite clay with red stains and 
 
 l)el)bles 
 
 Rnst-l>rown sandy clay with small 
 
 pebl)les 4 
 
 Red clay with some sand grains 3 
 
 Buff-colored, weathered 
 
 conglomerate 2 
 
 Red and buff mottled argillaceous 
 
 sandstone 1 
 
 P.rown-bnff argillaceous sandstone — 1 
 Light-buff, weathered 
 
 conglomerate 
 
 Yellow, weathered conglomerate 1 
 
 Dull-red and yellow, weathered con- 
 glomerate 
 
 Coarse-grained yellow sandstone con- 
 taining much clay 
 
 Dull-red conglomerate 1 
 
 Dull-red and yellow, weathered con- 
 glomerate 1 
 
 Diirk-yellow banded siltstone 
 
 Fine-grained dark gray rotten silt- 
 stone 
 
 Dark-gray very coarse rotten sand- 
 stone 1 
 
 Rotten, chalky-white conglomerate. 1 
 
 Rotten, diirk-gray conglomerate 1 
 
 Rotten, white conglomerate 1 
 
 Eocene (?) Unnamed pre-lone beds (?) 
 (Jreen and white w(>athere(l conglom- 
 erate 1 
 
 * No core, description from driller's log. 
 
 ckness 
 
 Depth 
 
 inches 
 
 feet 
 184 
 
 inches 
 
 2 
 
 185 
 
 2 
 
 4 
 
 188 
 
 6 
 
 6 
 
 189 
 
 
 9 
 
 190 
 
 9 
 
 4 
 
 191 
 
 1 
 
 11 
 
 193 
 
 
 9 
 
 197 
 
 9 
 
 11 
 
 2(K) 
 
 S 
 
 1 
 
 201 
 
 9 
 
 204 
 
 205 
 
 207 
 
 210 
 214 
 
 265 
 
 
 301 
 
 
 304 
 
 
 306 
 
 o 
 
 308 
 
 9 
 
 309 
 
 6 
 
 313 
 
 6 
 
 317 
 
 319 
 
 6 
 
 .321 
 
 »> 
 
 .322 
 
 
 
 32.", 
 
 
 324 
 
 
 
 324 
 
 6 
 
 325 
 
 
 :'.26 
 
 .", 
 
 .327 
 
 ;; 
 
 .",27 
 
 .",28 
 
 9 
 
 :'.30 
 
 
 6 
 
 :!3i 
 
 6 
 
 
 .3.",2 
 
 6 
 
 6 
 
 3.34 
 
 
 335 
 
loNE Formation, Buena Vista Area 
 
 HOLE 18-1 
 
 Approximately 1213 feet X. 73' E. of top of Ckitwood Hill, approxi- 
 mately 50 feet south of Kovaccvich north property line. Elevation 
 2oli feet. 
 
 29 
 
 Quaternary alluvium 
 
 Caving sand and gravel *_ 
 
 Eocene lone formation (?) 
 Upper lone member (?) 
 Green clay * 
 
 Thickness 
 feet inches 
 . 26 
 
 83 
 
 Lower lone member 
 
 Lignite ♦ 
 
 Lignite 
 
 Dark-gray carbonaceous clay 
 
 Gray clay, some sand 
 
 AVhite clay 
 
 Pale-brown clay 
 
 Urown clay 
 
 Lignite 
 
 Brown clay 
 
 Lignite 
 
 Brown clay 
 
 I'ale-brown clay 
 
 Ijight-gray sandy clay 
 
 (Jray sandy clay 
 
 Gray-green argillaceous sandstone 
 
 AVhite clay witlvsonie sand 
 
 Light-gray clay 
 
 Fine-grained light-gray sandstone 
 
 with clay cement 
 
 Light-gray clay 
 
 Dark-gray clay 
 
 Carbonaceous clay, some lignite 
 
 Carbonaceous clay with some sand 
 
 Carbonaceous clay 
 
 I>ignite with abundant clay 
 
 Carbonaceous day 
 
 Ivignite with abundant clay 
 
 (^arbonaceous clay 
 
 Lignitic clay 
 
 Slightly silty carbonaceous clay 
 
 Lignite with a few clay partings 
 
 Gray argillaceous sandstone 
 
 AVhite clay 
 
 AVhite sand with clay cement 
 
 Cream-colored cliiy 
 
 Cream-colored clay with iron nodules 
 
 Cream-colored clay 
 
 liight-gray clay with some sand 
 
 grains 
 
 Light-gray clay 
 
 Light-gray sandy clay 
 
 Light-gray clay very little sand 
 
 AVhite clay 
 
 AA'hite clay with dark brown specks; 
 
 2" peblde at 21.T 
 
 AA'hite clay with a 4" dark brown 
 
 fragment of wood at 215' (5" 
 
 Gray sandy, day 
 
 Gray sand with clay cement 
 
 Light-gray clay and sand 
 
 Light-gray sandy day with slight 
 
 yellow stain 
 
 Light-yellow clay with some sand 
 
 grains 
 
 Light-yellow sandy clay 
 
 14 
 
 — _ 1") 
 ___ 
 -__ 3 
 
 Depth 
 feet inches 
 26 
 
 109 
 
 6 
 
 
 115 
 
 
 3 
 
 
 118 
 
 
 
 
 3 
 
 118 
 
 3 
 
 4 
 
 9 
 
 123 
 
 
 3 
 
 
 126 
 
 
 3 
 
 6 
 
 129 
 
 6 
 
 
 
 6 
 
 130 
 
 
 
 
 3 
 
 130 
 
 3 
 
 
 
 8 
 
 130 
 
 11 
 
 1 
 
 
 131 
 
 11 
 
 1 
 
 4 
 
 133 
 
 3 
 
 6 
 
 3 
 
 139 
 
 6 
 
 1 
 
 « 
 
 141 
 
 
 2 
 
 
 143 
 
 
 1 
 
 6 
 
 144 
 
 G 
 
 6 
 
 (> 
 
 ir.i 
 
 
 
 
 3 
 
 i.ji 
 
 3 
 
 1 
 
 9 
 
 153 
 
 
 2 
 
 
 ir,.-. 
 
 
 
 
 r, 
 
 ir,5 
 
 6 
 
 (> 
 
 6 
 
 162 
 
 
 2 
 
 
 1(W 
 
 
 1 
 
 
 165 
 
 
 
 
 8 
 
 nr. 
 
 8 
 
 
 
 .''. 
 
 166 
 
 1 
 
 
 
 .3 
 
 166 
 
 4 
 
 
 
 8 
 
 167 
 
 
 1 
 
 S 
 
 16H 
 
 8 
 
 2 
 
 7 
 
 171 
 
 3 
 
 2 
 
 (> 
 
 173 
 
 9 
 
 1 
 
 9 
 
 175 
 
 6 
 
 6 
 
 
 IKl 
 
 6 
 
 1 
 
 
 182 
 
 6 
 
 P- 
 
 
 187 
 
 6 
 
 
 
 
 
 18K 
 
 
 1 
 
 
 189 
 
 
 ."! 
 
 (i 
 
 192 
 
 6 
 
 1 
 
 (i 
 
 194 
 
 
 1 
 
 »> 
 
 195 
 
 «> 
 
 2 
 4 
 
 10 
 
 19K 
 212 
 
 
 215 
 
 217 
 
 232 
 232 
 236 
 
 237 
 
 2.39 
 242 
 
 Thickness 
 feet inches 
 
 Light-yellow clay 5 
 
 Buff sandy clay 1 
 
 AVhite and buff clay 1 
 
 AVhite day 2 
 
 Buff silty clay with red stain 3 4 
 
 Light buff clay 3 6 
 
 AA'hite sandy clay some buff stain 2 9 
 
 AA'hite quartz gravel * 5 3 
 
 Carbonaceous argillaceous sand- 
 stone 1 
 
 AVhite argillaceous sandstone with 
 day chips and iron nodules 4 
 
 AA'hite siliceous sandstone, clay ce- 
 ment 2 G 
 
 Gray carbonaceous sUty clay with 
 
 some sand 3 G 
 
 Gray sandy clay 6 
 
 AVhite clay with some silt and col- 
 ored pebbles 9 
 
 Red sandy clay with buff spots 4 3 
 
 Red and buff day with some silt 4 6 
 
 Re<l, yellow, and white mottled 
 
 sandy day 3 3 
 
 AVhite sandy clay with yellow 
 
 stains, iron nodules 1 9 
 
 Dark-yellow sjindy clay with red and 
 white areas 4 
 
 A'ellow and white argillaceous silt- 
 stone 1 
 
 Weathered conglomerate; various 
 colored pebbles in pink to brown 
 matrix with transition to white 
 matrix between 297' and 298' 8 
 
 AVhite day with sand grains, some 
 
 pale green areas 2 3 
 
 Deep-red day with quartz pebbles 
 
 and white ])atches 5 9 
 
 Eocene (?) unnamed pre- lone beds 
 
 Reddish buff silty clay with some 
 
 pebbles 2 
 
 Yellow-brown clay with some sand 
 
 grains 1 
 
 AVhite clay with sand grains, light 
 
 buff stains 1 
 
 Yellow to reddish-yellow clay with 
 
 sand grains 2 
 
 AVhite sandy day 9 
 
 Yellow to reddish yellow clay with 
 
 sand grains 2 .3 
 
 \\'hit<' sandy clay 4 
 
 White day 7 
 
 (Jreen day 4 
 
 Greenish day with scattered sand 
 
 and pebbles 9 
 
 Greenish day with some sand 2 6 
 
 (ireeuish sandy silt with iron nod- 
 ules 20 9 
 
 Greenish silty day 10 
 
 (Jreenish white sandy clay with yel- 
 lowish stains G 
 
 Depth 
 feet inches 
 247 
 248 
 249 
 
 249 2 
 252 6 
 256 
 
 258 9 
 264 
 
 265 
 269 
 271 
 
 27;; 
 
 275 
 
 276 
 
 280 
 285 
 
 288 
 
 290 
 
 294 
 
 295 
 
 303 
 305 
 311 
 
 313 
 314 
 315 
 
 317 
 
 
 317 
 
 9 
 
 .320 
 
 
 324 
 
 
 331 
 
 
 335 
 
 
 .335 
 
 9 
 
 338 
 
 3 
 
 359 
 
 
 369 
 
 
 375 
 
 ♦ No core, description from driller's log. 
 
30 
 
 Special Report 19 
 
 HOLE 18-2 
 
 190 feet east of Ringer west property line, JiOO feel north of Jackson 
 Creek. Elev(^tion 270 feet. 
 
 Quaternary alluvium (?) 
 
 Sand and gravel * 
 
 Eocene lone formation 
 Lower lone member 
 
 Lignite * 
 
 Dark-gray carbonaceous clay 
 
 Lignite 
 
 Light-brown fine sandy clay 
 
 Lignite 
 
 Transition to pale-brown clay 
 
 Pale-brown clay 
 
 Very pale-brown clay; 
 
 Lignite 
 
 Brown clay 
 
 Lignite 
 
 Pale-brown clay with some silt 
 
 AVhite clay with small red areas 
 
 White clay 
 
 Pale-brown argillaceous silt 
 
 Pale-brown clay 
 
 Fragments of clay and lignite 
 
 Lignite with clay 
 
 Dark-gray carbonaceous clay 
 
 Lignite 
 
 No core 
 
 Lignite 
 
 Brown clay 
 
 Lignite 
 
 Brown clay 
 
 Lignite 
 
 Dark-brown silty clay 
 
 Lignite 
 
 Clay 
 
 Lignite 
 
 Dark-gray carbonaceous sandy clay 
 
 Lignite 
 
 Dark-gray carbonaceous sandy clay 
 
 lyignite 
 
 Brown carbonaceous sandy clay 
 
 Lignite 
 
 Brown sandy clay 
 
 Lignite 
 
 White conglomeratic clay 
 
 Fine-grained white argillaceous 
 
 sandstone 
 
 Fine-grained white sandy clay 
 
 Fine-grained white argillaceous 
 
 sandstone 
 
 White argillaceous medium-grained 
 
 sandstone with some buff stains 
 
 Gray carbonaceous medium-grained 
 
 sandstone 
 
 Thickness 
 feet inches 
 . 51 
 
 Depth 
 feet inches 
 51 
 
 a 
 
 
 54 
 
 
 
 
 ') 
 
 54 
 
 2 
 
 
 
 2 
 
 54 
 
 4 
 
 1 
 
 4 
 
 55 
 
 8 
 
 6 
 
 
 61 
 
 8 
 
 
 
 7 
 
 62 
 
 3 
 
 1 
 
 •J 
 
 64 
 
 
 in 
 
 
 79 
 
 
 1 
 
 2 
 
 80 
 
 2 
 
 1 
 
 10 
 
 82 
 
 
 
 
 3 
 
 82 
 
 3 
 
 1 
 
 9 
 
 84 
 
 
 10 
 
 
 94 
 
 
 5 
 
 
 99 
 
 
 fi 
 
 
 105 
 
 
 8 
 
 
 113 
 
 
 1 
 
 
 114 
 
 
 
 
 3 
 
 114 
 
 3 
 
 
 
 9 
 
 115 
 
 
 1 
 8 
 
 
 116 
 119 
 
 
 2 
 
 
 121 
 
 
 1 
 
 
 122 
 
 
 1 
 
 
 123 
 
 
 
 
 3 
 
 123 
 
 3 
 
 5 
 
 3 
 
 128 
 
 6 
 
 2 
 
 3 
 
 130 
 
 9 
 
 2 
 
 1 
 
 132 
 
 10 
 
 
 
 2 
 
 133 
 
 
 1 
 
 
 134 
 
 
 1 
 
 5 
 
 135 
 
 5 
 
 
 
 7 
 
 136 
 
 
 
 
 2 
 
 136 
 
 2 
 
 
 
 2 
 
 136 
 
 4 
 
 1 
 
 2 
 
 137 
 
 (> 
 
 1 
 
 
 138 
 
 6 
 
 1 
 
 5 
 
 139 
 
 11 
 
 4 
 
 1 
 
 144 
 
 
 1 
 
 
 145 
 
 
 8 
 
 3 
 
 153 
 
 3 
 
 
 
 9 
 
 154 
 
 
 12 
 
 
 166 
 
 
 3 
 
 •-> 
 
 169 
 
 U 
 
 4 
 
 9 
 
 174 
 
 
 Thickness 
 feet inches 
 
 Gray carlwnaceous medium-grained 
 sandstone with some buff stains 10 
 
 Dark-gray micaceous fine-grained 
 
 sandstone 9 
 
 Dark brownish-gray sandstone with 
 clay, some pebbles and some plant 
 remains 1 
 
 Light-brown clay with scattered 
 
 pebbles 
 
 Light-brown clay with abundant fine 
 sand and plant remains 9 
 
 Brownish carl)onaceous clay with 
 
 some pebbles 2 
 
 I>ark-gray carbonaceous siltstone 3 
 
 Dark-gray carbonaceous argillaceous 
 sand 1 
 
 Dark-red sand with carbonaceous 
 material 
 
 Dark-gray carbonaceous 
 
 argillaceous sand , 
 
 Dark-red sand with carbonaceous 
 
 material . 
 
 Dark-gray sandy clay with carbon- 
 aceous material 3 
 
 Fine-grained dark gray carbonaceous 
 sandstone with much clay 5 
 
 Lignite 
 
 Fine-grained dark-gray carbonace- 
 ous sandstone with much clay 4 
 
 Buff clay with some sand and small 
 iron nodules 1 
 
 Gradation to red and buff mottled 
 clay with some sand and iron 
 nodules 
 
 Red and buff mottled clay with some 
 sand and iron nodules 3 
 
 Red clay with some mottling and 
 iron nodules 2 
 
 White and red mottled clay with 
 iron nodules 1 
 
 Red clay with some sand 1 
 
 Dark-red clay with iron nodules 1 
 
 Eocene (?) unnamed pre-lone beds 
 Transition to green unaltered con- 
 glomeratic material 
 
 Green conglomeratic material 3 
 
 AVhitish-green conglomeratic 
 
 material 5 
 
 Buff sandy clay 2 
 
 Olive-l)rown sandy clay, some 
 
 pebl)Ies 5 
 
 Grayish l)uff-i)rown silty clay 2 
 
 Depth 
 feet inches 
 
 184 
 193 
 
 194 
 
 
 194 
 
 9 
 
 204 
 
 
 206 
 209 
 
 
 210 
 
 3 
 
 210 
 
 6 
 
 210 
 
 8 
 
 211 
 
 
 214 
 
 
 219 
 219 
 
 4 
 5 
 
 224 
 
 
 225 
 
 4 
 
 225 
 
 9 
 
 229 
 
 
 231 
 
 3 
 
 232 
 234 
 235 
 
 10 
 
 6 
 
 235 
 
 6 
 
 239 
 
 
 244 
 
 6 
 
 246 
 
 6 
 
 252 
 
 
 254 
 
 • No core, description from driller's log. 
 
loNE Formation, Buena Vista Area 
 
 31 
 
 HOLE 18-3 
 
 200 feet N. of county road and 190 feet E. of Hart west property 
 line. Elevation 321 feet. 
 
 Thickness Depth 
 
 Quaternary terrace gravel feet inches feet inches 
 
 Sand and gravel * 15 15 
 
 Eocene lone formation 
 Upper lone member 
 
 White to gray-green clay * 52 67 
 
 Lower lone member (?) 
 
 Sand • 8 75 
 
 Clay* 3 78 
 
 Lower lone member 
 
 Lignite* 11 89 
 
 Clay, sandy clay, and silt * 27 116 
 
 Clay, silt, and gravel beds * 18 134 
 
 Brown ironstone, extremely hard ; 
 
 many quartz grains * 9 143 
 
 Rust-colored medium-grained sand- 
 stone cemented with iron oxide 
 
 and clay 20 163 
 
 Coarse-grained sandstone with heavy 
 
 iron-oxide cement 2 8 16.") 8 
 
 White clay with some silt 2 1 167 9 
 
 White clay with a few sand grains ; 
 
 heavy yellow stain 2 3 170 
 
 Buff silty clay with purple stain 2 172 
 
 Light-buff silty clay with red stains 1 6 173 6 
 
 Red and white clay G 6 180 
 
 A'ery light buff clay with red stains 3 183 
 
 Light-buff clay with red stains 1 184 
 
 Light-buff clay with sand grains, red 
 
 stains 1 185 
 
 Red, white, and buff mottled clay___ 2 1 187 1 
 Light-buff clay with sand grains, red 
 
 stains 11 188 
 
 Light-buff clay with red and dark 
 
 buff strains 2 1 190 1 
 
 Very light-buff sandstone, very little 
 
 clay cement 6 4 196 5 
 
 White clay 1 5 197 9 
 
 Sand parting 1 197 10 
 
 White clay 2 2 200 
 
 Light-buff clay with some sand 
 
 grains 1 6 201 6 
 
 Light-buff argillaceous sandstone 6 202 
 
 White silty clay 1 203 
 
 Cream-colored silty clay 9 203 9 
 
 Cream-colored fine-grained sandy 
 
 clay 1 6 205 3 
 
 Cream-colored' coarse-grained sandy 
 
 clay 1 5 206 8 
 
 Cream-colored clay 7 207 3 
 
 Cream-colored clay with red stain__ 9 208 
 Cream-colored clay with sand grains 
 
 and red stain 5 208 5 
 
 Light-buff sandstone with clay ce- 
 ment and red stains 7 209 
 
 Fine-grained white argillaceous 
 
 sandstone 20 5 229 5 
 
 Depth 
 feet inches 
 
 230 
 
 2 
 
 233 
 236 
 
 6 
 
 244 
 
 
 247 
 
 9 
 
 248 
 
 6 
 
 250 
 
 6 
 
 254 
 
 
 258 
 264 
 
 
 267 
 
 8 
 
 274 
 
 
 Thickness 
 feet inches 
 
 I-ignite with sand parting at 229' 10" 9 
 
 (Jray medium-grained sand with lig- 
 nite seams at 231' 2" and 231' 5"__ 3 4 
 
 Light-gray argillaceous siltstone 2 6 
 
 Fine-grained dark-gray carbona- 
 ceous argillaceous sandstone 8 
 
 Lignite and dark-gray clay 
 
 alternating 3 9 
 
 Gray argillaceous sandstone alter- 
 nating with lignite seams 9 
 
 Gray medium-grained sandstone 
 
 with yellow stain 2 
 
 Fine-grained gray standstone with 
 
 lignite as thin partings 3 6 
 
 Fine-grained gray carbonaceous 
 
 sandstone 4 
 
 Dark-gray carbonaceous sandy clay 6 
 
 Dark-gray carbonjiceous silty clay 
 
 with numerous lignite partings 3 8 
 
 Highly carbonaceous sandy clay 
 
 with lignite partings 6 4 
 
 Jurassic Mariposa slate 
 
 I'iiikish-stained clay grading to grav 
 
 clay "_ 3 6 
 
 Gray clay red-stained in places 1 
 
 Olive-colored clay with red stain 1 6 
 
 Pinkish-clay with iron specks 4 
 
 Olive-colored clay 7 6 
 
 Olive-colored clay, some sand grains 1 6 
 
 I'inkish clay, some sand 1 
 
 Olive-colored clay, some sand 10 
 
 • No core, description from driller's log. 
 
 HOLE 18-4 
 
 50 feet E. of range line hettceen If. 9 E. and l{. 10 E. (projected) : 
 2J,0 feet N. of north side of sec. 19, T. 5 .V., K. 10 E. Elevation 258 
 feet. 
 
 Thickness Depth 
 
 feet inches feet inches 
 Xo core 180 180 
 
 Eocene lone formation 
 Lower lone member 
 Clay * 14 194 
 
 Dirtv white clay with one 3-inch 
 
 pebble 4 198 
 
 White clay with abundant iron nod- 
 ules 3 201 
 
 White clay 3 204 
 
 White clay with fine to coarse sand 
 
 grains 6 210 
 
 White clay 10 210 10 
 
 White clay with iron veinlets 1 211 W 
 
 White day with some sand grains 1 11 213 9 
 
 Jurassic Amador group 
 
 Residual clay ; mostly white ; some 
 
 green 6 214 3 
 
 • Nil core, description from driller's log. 
 
 277 
 
 6 
 
 278 
 280 
 
 6 
 
 284 
 291 
 
 6 
 
 293 
 
 
 294 
 
 
 304 
 
 
32 
 
 Special Report 19 
 
 HOLE 19-1 
 
 60 feet E. of Ringer west property line, 100 feet S!. of south boundary 
 of Buena Vista Grant. Elevation 327 feet. 
 
 Thickness Depth 
 
 Eocene lone formation feet inches feet inches 
 Upper lone member (?) 
 
 Sand and frravel * 16 IG 
 
 Sand and clay * 74 90 
 
 Lower lone member 
 
 I-ignite * 5 9r» 
 
 Sand and day * 24 110 
 
 Lignite ♦ 14 l.SS 
 
 Clay * ir, 148 
 
 Lignite * 6 l."')4 
 
 Clay* 21 17r. 
 
 Sand and clay * 60 235 
 
 Sand and pebbles, increasing in 
 
 coarseness downward. Very coarse 
 
 at 265'* 30 265 
 
 Eocene (?) unnamed pre-lone beds 
 
 Gray medium-grained sandstone 
 
 with pebbles 265 9 
 
 Fine-grained olive buff micaceous 
 
 sandstone 4 3 270 
 
 Buff sand with lenses of biotite 5 275 
 
 Sand and pebbles * 9 284 
 
 Glauconitic green sand grading 
 
 downward into a gray plastic 
 
 clay * 30 314 
 
 Gray plastic clay * 11 325 
 
 (Jreen and brown dense siltstone 11 336 
 
 Gray plastic clay * 54 390 
 
 Jurassic Amador group 
 
 Greenstone 6 396 
 
 • No core, description from driller's log. 
 
 HOLE 24-1 
 
 2810 feet S. 1,0° 11'. from hole 18-1. Approximately 95 feet W. of 
 Hart east property line. Elevation 269 feet. 
 
 Thickness Depth 
 
 Eocene lone formation (?) feet inches feet inches 
 
 Upper lone member (?) 
 
 Sand and gravel * 82 82 
 
 Lower lone member (?) 
 
 Red clay * 4 6 S6 6 
 
 Jurassic Amador group (?) 
 
 Bed rock * 16 SS 
 
 * No core, description from driller's log. 
 
 HOLE 24-2 
 
 Approximately 1660 feet S. 12° E., from the top of Chittvood Hill. 
 Elevation 275 feet. 
 
 Thickness Depth 
 
 Eocene lone formation (?) feet inches feet inches 
 
 Upper lone member (?) 
 
 Sand and gravel * 32 32 
 
 Greenish silty clay * 12 44 
 
 Pale-buff clay 16 45 6 
 
 Thickness 
 feet inches 
 
 Yellow-brown clay with some silt__ 2 
 Yellow-brown argillaceous s a n d- 
 
 stone 7 
 
 Olive-brown silty clay 4 11 
 
 Eocene lone formation 
 Lower lone member 
 
 Fine-grained gray argillaceous sand- 
 stone 1 
 
 Gray medium-grained sandstone 
 
 with clay cement 1 
 
 Light-gray silty clay 6 
 
 Ijight gray clay with pieces of lignite 2 6 
 
 Lignite 8 
 
 Jjight-gray carbonaceous clay 4 
 
 liight-gray silty clay 1 4 
 
 Light-gray argillaceous medium- 
 grained sandstone 10 
 
 Fine-grained light-gray argillaceous 
 
 sandstone 5 
 
 Light-gray argillaceous medium- 
 grained sandstone 5 
 
 Light-gray clay 2 
 
 Fine-grained light gray argillaceous 
 
 sandstone : 3 10 
 
 Fine-grained gray argillaceous sand- 
 stone 9 
 
 Light-gray carbonaceous clay with 
 
 some silt 1 8 
 
 Lignite 2 
 
 Light-gray carbonaceous clay with a 
 
 little fine silt 3 2 
 
 Light-gray carbonaceous clay 2 
 
 liight-brown clay 4 
 
 Lignite 4 8 
 
 Dark-brown clay 5 
 
 liignite 3 
 
 Brown clay 7 
 
 Lignite 1 3 
 
 Dark-brown clay 2 
 
 I..ignite 4 6 
 
 Dark-brown carbonaceous clay 6 
 
 laght-brown clay 3 7 
 
 Pale-brown sandy clay 6 
 
 Very light gray silty clay with iron 
 
 specks 9 
 
 AVhite sandy clay with iron nodules 8 
 White sandy clay with red clay frag- 
 ments and iron nodules 2 
 
 White clay with red stain and iron 
 
 nodules 4 
 
 White sandy clay with iron nodules 2 
 
 White clay 2 
 
 AVhite clay with some silt 2 6 
 
 A'ery light buff silty clay 8 
 
 White clay with some silt 1 4 
 
 White clay with some silt and some 
 
 iron nodules 1 4 
 
 Very light buff silty clay 2 2 
 
 White clay, conchoidal fracture 1 
 
 AVhite clay with some silt 7 2 
 
 Jurassic Amador group 
 
 Altered greenstone 7 
 
 Fresh greenstone 2 1 
 
 • No core, description from driller's log. 
 
 Depth 
 feet inches 
 
 47 6 
 
 48 1 
 53 
 
 54 
 
 55 
 
 
 55 
 
 6 
 
 58 
 
 
 58 
 
 8 
 
 62 
 
 8 
 
 64 
 
 
 74 
 
 
 79 
 
 
 84 
 
 
 84 
 
 2 
 
 88 
 
 97 
 
 98 
 
 8 
 
 98 
 
 10 
 
 102 
 
 
 104 
 
 
 104 
 
 4 
 
 100 
 
 
 109 
 
 5 
 
 112 
 
 5 
 
 113 
 
 
 114 
 
 3 
 
 114 
 
 5 
 
 118 
 
 11 
 
 119 
 
 5 
 
 123 
 
 
 129 
 
 
 138 
 
 
 146 
 
 
 148 
 
 152 
 
 
 154 
 
 
 156 
 
 
 158 
 
 6 
 
 159 
 
 2 
 
 160 
 
 6 
 
 161 
 
 10 
 
 164 
 
 
 165 
 
 
 172 
 
 2 
 
 172 
 
 9 
 
 174 
 
 10 
 
loNE Formation, Buena Vista Area 
 
 33 
 
 HOLE 24-3 
 
 50 feet ir. of county road and 100 feet «S'. of Kidd north property line. 
 Elevation 213 feet. 
 
 Eocene lone formation 
 Upper lone member 
 
 Light-buff sandy day * 14 
 
 Red ferruginous conglomeratic sand- 
 stone 
 
 White, iron-stained, coarse sand- 
 stone 
 
 White, iron-stained, sandy clay, 
 sand grains becoming coarser and 
 more al)undant after V.V (i" 5 
 
 White, iron-stained, argillaceous 
 sandstone 1 
 
 Greenish-tan silty clay with almost 
 no sand grains 
 
 Ferruginous sandstone 1 
 
 Olive-brown clay 
 
 White, iron-sfaiiied, argillaceous 
 fine-grained sandstone 
 
 Light-brown silty clay 
 
 Light olive-brown clay with some 
 silt 1 
 
 Reddish-brown ferruginous sandy 
 clay 1 
 
 Dark-buff sandy clay 
 
 Fine-grained' greenish argillaceous 
 sandstone with yellow stain 2 
 
 Fine-grained greenish argillac-eous 
 sandstone 7 
 
 Greenish medium-grained sandstone 
 
 Greenish coarse-grained angular 
 sandstone, poorly cemented with 
 clay 
 
 Buff medium-grained sandstone 
 with a little day cement 4 
 
 Fragments of buff coarse-grained 
 sandstone with a little clay cement 
 (poor core recovery) 10 
 
 Huff medium-grained argillaceous 
 sandstone with yellow stains .'{ 
 
 Buff clay with a few sand grains 2 
 
 Olive-buff clay with some sand 
 grains 2 
 
 Greenish-buff fine-grained argilla- 
 ceous sandstone 1 
 
 Clay with abundant sand grains 1 
 
 Medium-grained argillaceous sand- 
 stone 1 
 
 Coarse-grained sandstone with 
 brown stain 1 
 
 Gray-buff sandy day 
 
 Coarse-grained sandstone with 
 brown stain 
 
 Gray-buff sandy day with sand 
 grains more abundant after 79' 3" .'$ 
 
 Sand and clay fragments (poor core 
 recovery) 3 
 
 Dark-buff sandy clay \^ 
 
 Dark-buff day 1 
 
 liight-buff day with small red areas 2 
 
 Silty day 
 
 Fine sandy clay 1 
 
 Clayey sandstone 1 
 
 Buff clay with some silt 
 
 Thickness 
 feet inches 
 
 11 
 
 10 
 
 10 
 
 Depth 
 feet inches 
 
 14 
 
 14 {) 
 
 15 6 
 
 20 
 21 
 
 2H 
 24 
 
 80 
 
 :{() 
 
 32 
 
 3:! 
 34 
 
 30 
 
 43 
 44 
 
 no 
 
 54 
 
 04 
 
 07 
 6U 
 
 71 
 
 M 
 
 
 S4 
 
 
 87 
 
 
 88 
 
 
 
 !)() 
 
 
 
 !)l 
 
 
 02 
 
 
 03 
 
 
 
 93 
 
 10 
 
 1 
 
 4 
 
 10 
 
 Thickness 
 feet inches 
 
 
 
 F 
 
 Dark-buff medium-grained sandy 
 
 clay 
 
 Hard, gray, medium-grained sand- 
 stone with buff stains 
 
 Soft, dark-buff medium-grained 
 
 sandstone 
 
 Dark-buff clay 
 
 White clay 1 
 
 AVhite clay with sand grains 
 
 Greenish-gray sand with clay 
 cement, grades from fine- to 
 coarse-grained 7 
 
 Lower lone member 
 
 Gray coarse-grained (|uartz sand- 
 stone with clay grains that re- 
 semble weathered feldspar grains 
 ine-grained white sand with buff 
 stains and a few partings of 
 
 coarse sand 
 
 Gray-brown carbonaceous clay 
 
 Carbonaceous brown clay 
 
 Gray-brown carbonaceous clay 
 
 Lignite 
 
 Brown clay grading downward to 
 
 white clay 
 
 Wliite clay with some sand grains__ 
 White silty clay with some yellow 
 
 stains 
 
 Light-brown clay 
 
 White clay with some sand grains 
 
 White day 
 
 White day with iron nodules 
 
 AVhite clay with a few large iron 
 
 nodules 
 
 Reddish buff and gray mottled clay, 
 some iron nodules (reworked 
 
 laterite) 
 
 Red and white clay with s|)ecks of 
 
 iron oxides (reworked laterite) __ 
 
 Red and white mottled clay with 
 
 abundant iron nodules (reworked 
 
 laterite) ' 
 
 Red with some white areas (re- 
 worked laterite) 
 
 A\'hite day mottled with some red 
 
 day (reworked laterite) 
 
 Red, gray, and cream clay (re- 
 worked laterite) 
 
 Yellow and red clny 
 
 Brown clay 
 
 Red smooth clay with conchoidal 
 
 fracture 
 
 Dark-buff and purple mottled clay__ 
 Yellowish day with red stain and 
 
 white spots 
 
 Red and white clay 
 
 Claylike material with pebbles of 
 greenstone and quartz 
 
 Jurassic Amador group 
 
 Greenstone 
 
 4 
 
 
 3 
 
 5 
 
 
 
 1 
 
 
 
 S 
 
 
 
 s 
 
 10 
 
 
 11 
 
 
 G 
 
 
 3 
 
 s 
 
 
 
 5 
 
 1 
 
 1 
 
 
 
 (! 
 
 
 
 5 
 
 13 
 
 11 
 
 10 
 
 
 10 
 
 
 Depth 
 feet inches 
 
 04 
 
 04 4 
 
 04 
 05 
 96 
 97 
 
 104 
 
 110 
 
 144 
 
 220 
 
 222 
 
 8 
 
 4 
 
 10 
 
 114 
 
 
 117 
 
 5 
 
 117 
 
 6 
 
 118 
 
 2 
 
 118 
 
 10 
 
 124 
 
 
 127 
 
 
 131 
 
 3 
 
 133 
 
 
 130 
 
 
 138 
 
 
 141 
 
 7 
 
 147 
 
 
 157 
 
 
 168 
 
 
 174 
 
 
 177 
 
 8 
 
 178 
 170 
 170 
 
 1 
 2 
 
 8 
 
 l.so 
 
 104 
 
 1 
 
 204 
 214 
 
 
 * No core, description from driller's log. 
 
34 
 
 Special Report 19 
 
 HOLE 24-4 
 
 UiO feet W. of Churchman east properly line and 380 feet N. of 
 Churchman south property line. Elevation 290 feet. 
 
 2 
 
 8 
 
 16 
 
 10 
 3 
 
 Thickness 
 feet inches 
 Miocene (?) Valley Springs formation 
 Bright blue-green clays, silts, and 
 sands * 100 
 
 Eocene lone formation (?) 
 Upper lone member (?) 
 
 Green sand, silt, and siliceous clay 
 and some gravel beds * 26 
 
 Olive-buff fine-grained sandstone 
 
 with some well-rounded pebbles. _ 4 6 
 
 Olive-buff sandstone with a very few 
 small pebbles, some pebbles weath- 
 ered to clay 8 
 
 Olive-buff siltstone and some pebbles o 
 
 Conglomerate with buff silty matrix, 
 dark-colored siliceous pebbles less 
 than 3" in diameter 6 
 
 Olive-buff fine-grained sandstone 
 
 Conglomerate with buff-colored silty 
 matrix, dark-colored siliceous peb- 
 bles 2 
 
 Yellowish fine-grained sandstone 
 with brown stains 1 
 
 Cream-colored silty clay with buff 
 stains 4 
 
 Cream-colored silty clay with buff 
 stains and some pebl)les 5 
 
 Light-brown conglomerate 4 
 
 Light-brown silty clay ; color grades 
 downward to brown 4 
 
 Mixed fragments of olive-brown silt 
 and clay 2 
 
 Olive-colored silty clay -1 10 
 
 Light olive-brown argillaceous sand- 
 stone 8 
 
 Conglomerate with olive-colored 
 matrix 1 
 
 Green-gray fine-grained argillaceous 
 sandstone with some black cari)oii- 
 aceous matter 7 
 
 Green-gray silty clay 2 
 
 Green-gray silty clay with sand 
 grains 
 
 liight olive-buff siltstone 
 
 Light olive-buff fine-grained sand- 
 stone 
 
 Gray-brown fine-grained argillaceous 
 sandstone 
 
 I>ight olive-gray fine-grained sandy 
 clay 
 
 Light olive-gray fine-grained silty 
 clay with finely disseminated 
 Iiyrite 
 
 liight olive-gray fine-grained silty 
 clay 
 
 Olive-brown clay with some silt 
 
 Olive-brown finer-grained argilla- 
 ceous sandstone 
 
 Olive-brown coarse-grained sand- 
 stone 
 
 Olive-colored fine-grained sandy clay 
 
 Eocene lone formation 
 
 Lower lone member (?) 
 
 Light buff argillaceous sandstone, 
 
 coarsest at top of bed 2 6 
 
 Light-buff clay 9 
 
 6 
 6 
 
 10 
 2 
 
 6 
 6 
 3 
 
 Depth 
 feet inches 
 
 100 
 
 126 
 
 130 
 
 131 
 134 
 
 141 
 141 
 
 143 
 
 14;-) 
 
 149 
 
 154 
 158 
 
 162 
 
 104 
 174 
 
 182 
 
 184 
 
 191 
 193 
 
 196 
 
 204 
 
 207 
 224 
 227 
 
 231 
 
 10 
 
 5 
 
 6 
 
 236 
 
 
 
 2 
 
 
 
 239 
 
 
 3 
 
 6 
 
 242 
 
 6 
 
 
 
 6 
 
 243 
 
 
 1 
 
 6 
 
 244 
 
 6 
 
 247 
 247 
 
 Thickness Depth 
 
 feet inches feet inches 
 Light-huff argillaceous sandstone, 
 
 coarser toward the l)ase 4 3 252 
 
 Light-buff clay 2 254 
 
 Lower lone member 
 
 Purple-brown cari)onaceous clay 
 with some lignite 
 
 I^ight gray clay 
 
 I-ignite with some clay 
 
 Gray clay ; some plant fragments 
 
 I>ight-gray clay 
 
 I^ight-gray sandy clay 
 
 Gray sandy clay with plant frag- 
 ments 
 
 Lignite 
 
 liight-gray clay 
 
 Light-gray argillaceous sandstone__ 
 
 Olive-brown sandy clay 
 
 IJght-gray argillaceous sandstone 
 
 Brr)wn carl)onace<)us clay 
 
 I^ight-gray silty clay — 
 
 Krown carbonaceous clay with lig- 
 nite partings 
 
 IMack highly carbonaceous clay 
 
 Light-gray sandy clay 
 
 I>ight-gray clay with coarse sand 
 
 Light-gray clay with iron nodules 
 and sand 
 
 Jjight-gray sandy clay 
 
 Tan argillaceous medium-grained 
 sandstone 
 
 Lignite 
 
 Brown medium-grained sandstone 
 with clay cement 
 
 Medium-grained brownish-gray ar- 
 gillaceous sandstone 
 
 Highly carbonaceous coarse-grained 
 sandstone 
 
 Xo core 
 
 Brownish-gray medium-grained 
 sandstone with much carbona- 
 ceotis material 
 
 Dark-brown highly carbonaceous 
 shale and lignite 
 
 Brownish-gray coarse-grained sand- 
 stone with carbonaceous material 
 
 Fragments of coarse-grained, pel)bly 
 sandstone, dark carlionaceous clay, 
 and sandstone (poor core recov- 
 ery) 
 
 Brown carbonaceous clay 
 
 I>ight-brown clay with some sand 
 and many jilant fragments 
 
 Gray sandy clay with many plant 
 fragments 
 
 Gray argillaceous sandstone with 
 plant fragments 
 
 J>ight-gray conglomerate 
 
 Light-gray argillaceous sandstone 
 
 Light-gray argillaceous sandstone 
 with rust-brown stain 
 
 Medium-grained argillaceous sand- 
 stone 
 
 Jurassic Amador group 
 
 Green, gray, red, and yellow weath- 
 ered agglomerate ; some pyrite 5 344 
 
 3 
 
 
 257 
 
 
 
 
 6 
 
 257 
 
 6 
 
 •> 
 
 3 
 
 260 
 
 9 
 
 1 
 
 
 261 
 
 9 
 
 *> 
 
 o 
 
 264 
 
 
 
 
 7 
 
 264 
 
 7 
 
 
 
 S 
 
 265 
 
 3 
 
 
 
 3 
 
 265 
 
 6 
 
 1 
 
 4 
 
 266 
 
 10 
 
 3 
 
 7 
 
 270 
 
 .5 
 
 
 
 :>, 
 
 270 
 
 8 
 
 .-{ 
 
 3 
 
 273 
 
 11 
 
 1 
 
 2 
 
 275 
 
 1 
 
 o 
 
 8 
 
 278 
 
 9 
 
 1 
 
 10 
 
 280 
 
 7 
 
 
 
 (> 
 
 281 
 
 1 
 
 *} 
 
 11 
 
 284 
 
 
 4 
 
 6 
 
 288 
 
 6 
 
 1 
 
 
 289 
 
 6 
 
 1 
 
 2 
 
 290 
 
 8 
 
 3 
 
 •» 
 
 293 
 
 11 
 
 1 
 
 2 
 
 295 
 
 1 
 
 6 
 
 11 
 
 302 
 
 
 O 
 
 
 305 
 
 
 
 
 
 
 ,305 
 
 G 
 
 
 
 U 
 
 312 
 
 
 1 
 
 7 
 
 313 
 
 7 
 
 
 
 8 
 
 314 
 
 o 
 
 
 
 9 
 
 315 
 
 
 10 
 
 
 325 
 
 
 
 9 
 
 325 
 
 1 
 
 8 
 
 327 
 
 1 
 
 7 
 
 329 
 
 1 
 
 8 
 
 330 
 
 
 
 4 
 
 .331 
 
 2 
 
 5 
 
 333 
 
 
 
 7 
 
 334 
 
 5 
 
 
 339 
 
 * No core, description from driller's log. 
 
loNE Formation, Buena Vista Area 
 
 35 
 
 HOLE 24-5 
 
 180 feet E. of county rond and t^O feet S. of north aide of sec. 2//, 
 T. 5 N., K. 9 E., Elevation 260 feet. 
 
 Thickness Depth 
 
 Eocene lone formation feet inches feet inches 
 
 Lower lone member 
 
 I^aterite ( rfworked ) * 4 4 
 
 Ked aiul l)iiff mottled clay ( reworked 
 
 laterite) 8 12 
 
 Red, huff, and purple mottled clay 
 
 (reworked hiterite) S 20 
 
 Red and buff mottled clay (reworked 
 
 laterite) 10 30 
 
 Red clay with some mottling (re- 
 worked laterite) 10 40 
 
 Red, yellow, and purple mottled clay 
 
 with some sand grains (reworked 
 
 laterite) 14 54 
 
 Red and buff mottled clay (reworked 
 
 laterite) 4 58 
 
 Jurassic Amador group 
 
 Red and buff mottled day (laterite) .") 63 
 
 Fresh greenstone 1 64 
 
 • No core, description from driller's log. 
 
 HOLE 24-6 
 
 30 feet W. of Churchman east property line, 1,')H feet S. of 
 Church man north property line. Elevation 277 feet. 
 
 Thickness Depth 
 
 Quaternary soil feet inches feet inches 
 
 Surface sand and gravel * 6 6 
 
 Miocene (?) Valley Springs formation 
 
 (Jreen clays, silts, and sands * ."iT Kj 
 
 Olive-brown tinc-grained sandstone 
 
 with clay cement 21 84 
 
 Olive-brown coarse-grained sand- 
 stone with clay cement 1 85 
 
 Olive-lirown conglomeratic fine- 
 grained sandstone 5 00 
 
 Olive-brown silty clay 7 97 
 
 P Olive-buff silty clay 7 104 
 IJght olive-buff silty clay with clay 
 
 fragments 4 108 
 
 Thickness 
 feet inches 
 Eocene lone formation (?) 
 Upper lone member (?) 
 
 Light-buff coarse-grained sandstone 
 
 with some clay cement 1 
 
 Greenish-buff coarse-grained sand- 
 stone with much l)iotite 1 7 
 
 Buff argillaceous fine-grained sand- 
 stone 10 
 
 (Ireenish-buff silty clay 4 7 
 
 Light-greenish-white clay san<l 1 (? 
 
 Light-olive-buff mixed sand and clay 2 ."> 
 
 Light-olive-buff silty clay 1 3 
 
 liight-olive-buff sandy clay 2 10 
 
 Grey biotitic sandstone with a little 
 clay cement and disseminated 
 
 pyrite 9 1 
 
 I-ight-buff clay with disseminated 
 
 pyrite 11 
 
 Light-olive-buff silty clay with 
 
 patches of disseminated pj'rite 4 
 
 I-ight-olive-buff sandy clay with oc- 
 cjisional siliceous and clay lu'bbles. 
 
 Patches of disseminated i)yrite (i 
 
 Olive-brown silty clay with biotite, 12 
 
 Light -brown silty clay 1 1 
 
 Light-l)rownish-buff clay with hiotite 4 11 
 Liglit-l)rown fine-grained sandy clay 2 G 
 
 Fine-grained olive-buff argillaceous 
 
 liiotitic sandstone 2 3 
 
 Olive-buff conglomerate with clay 
 and sand matrix. Weathered and 
 siliceous pebbles up to 2" in diam- 
 eter 7 3 
 
 Olive-brown conglomeratic clay 7 
 
 Red and white mottled clay with oc- 
 casional ])ebbles 3 
 
 Olive-buff medium-grained sandstone 
 
 with biotite 7 
 
 Clay-pebble conglomerate G 
 
 Lower lone member 
 
 Red, white, and buff coarsely mot- 
 tled clay (reworUeil laterite) S 1 
 
 Red anil buff mottled clay (reworked 
 laterite I. A 1" pebble iit 10.3' 1(1 
 
 Re<l, white, and buff mottled clay 
 (reworked laterite | 5 
 
 Red clay with small white patches 
 (reworked laterite). A 1)/' water 
 worn i)ebble at 214' 22 
 
 Jurassic Amador group 
 
 Highly weathered greenstone G 
 
 Fresh greenstone G 
 
 • No core, description from driller's log. 
 
 Depth 
 feet inches 
 
 109 
 
 110 
 
 111 
 
 5 
 
 116 
 
 
 117 
 
 G 
 
 119 
 
 11 
 
 121 
 
 2 
 
 124 
 
 
 133 
 
 1 
 
 134 
 
 
 138 
 
 
 144 
 
 
 156 
 
 
 157 
 
 1 
 
 1G2 
 
 
 1G4 
 
 6 
 
 1(>G 
 
 174 
 174 
 
 174 
 
 175 
 175 
 
 1S4 
 194 
 199 
 
 221 
 
 221 
 
 10 
 
 n 
 11 
 
 I 
 
 I 
 
36 
 
 Special Report 19 
 
 HOLE 24-7 
 
 Approximate!!/ 50 feet W. of county rond and I 'lOO feet K. of hole 2'i-3. 
 Elevation 300 feet. 
 
 Thicknesx 
 Quaternary terrace gravel feet inches 
 
 Gravel with boulders * 8 
 
 Miocene (?) Valley Springs formation 
 
 Yellow clayey silt * 7 
 
 Gray siliceous clay * 10 
 
 Eocene lone formation (?) 
 Upper lone member (?) 
 
 Buff siliceous clay * 10 
 
 Buff clay * 10 
 
 Greenish-gray clay and silt * 10 
 
 Gray sandy silt * 10 
 
 Greenish silty clay * 10 
 
 Greenish-Kray silt grading down- 
 ward into sand * 20 
 
 Clay and sand * 98 
 
 Lower lone member 
 Lignite * 
 
 Clay* 
 
 Gray medium-grained micaceous 
 sandstone with carbonized plant 
 
 fragments 
 
 Gray clay with carbonaceous mate- 
 rial 
 
 lagnite 
 
 Gray clay with carbonaceous mate- 
 rial 
 
 I>ight gray fine-grained sandstone 
 
 Light-gray argillaceous medium- 
 grained sandstone 
 
 Light-gray medium-grained sand- 
 stone with some clay 
 
 Light-gray argillaceous medium- 
 grained sandstone 
 
 Light-gray medium-grained sand- 
 stone with some clay 
 
 Light-gray clay with red stains and 
 
 some sand 
 
 Ligiit-buff clay with red and purple 
 s])<its (weathered conglomerate). 
 I-ight-buff coarse-grained argilla- 
 ceous sandstone with some red 
 
 stain 
 
 AVhite medium-grained argillaceous 
 
 sandstone with some red stains 
 
 White sandy clay 
 
 Brown silty clay with white and yel- 
 low areas 
 
 No core 
 
 AVhite sandy clay 
 
 (Jreenish-gray clay with coarse sand 
 
 grains 
 
 White clay with coarse sand grains 
 
 lirown clay 
 
 Green-l)rowu conglomerate with clay 
 
 matrix 
 
 Chalky white conglomerate and clay 
 
 mixture 
 
 P.rown clay with some red stain 
 
 (Jray argillaceous sandstone 
 
 Yellow-brown clay 
 
 Coarse-grained angular quartzose 
 sandstone with red cementing min- 
 eral 
 
 Red and yellow l)rown silty clay 
 
 Gray weathere<l conglomerate 
 
 Olive buff silty clay with iron 
 nodules, fewer iron nodules below 
 
 White sandy clay with red and yel- 
 low stains and a few iron nodules 
 'White sandy clay with red stains 
 
 (1 
 1(5 
 
 10 
 
 2 
 
 fi 
 
 1 
 
 l(t 
 
 1 
 
 »> 
 
 
 
 5 
 
 
 
 3 
 
 
 
 4 
 
 
 
 4 
 
 4 
 
 G 
 
 
 
 S 
 
 Depth 
 feet i)tchcs 
 
 ir. 
 25 
 
 65 
 
 75 
 
 95 
 193 
 
 100 
 215 
 
 2 
 
 
 227 
 
 1 
 
 2 
 
 228 
 
 1 
 
 11 
 
 230 
 
 *> 
 
 11 
 
 233 
 
 ;} 
 
 
 230 
 
 4 
 
 
 240 
 
 1 
 
 
 241 
 
 1 
 
 5 
 
 242 
 
 
 
 7 
 
 243 
 
 4 
 
 10 
 
 247 
 
 2 
 
 1 
 
 249 
 
 2 
 
 1 
 
 252 
 
 5 
 
 7 
 
 2(!1 
 
 1 
 
 2 
 
 2G2 
 
 2 
 
 4 
 
 2(!4 
 
 (1 
 
 (! 
 
 2(;5 
 
 1 
 
 5 
 
 260 
 
 208 
 
 280 
 
 2sn 
 2S3 
 
 10 
 
 11 
 
 271 
 
 
 272 
 
 10 
 
 274 
 
 
 274 
 
 5 
 
 274 
 
 8 
 
 275 
 
 4 
 
 11 
 
 'rhicknexx 
 feet inches 
 I'nrple, red. and buff mottled clay 
 
 (reworked (?) laterite) 1 
 
 Red-buff clay (reworked (?) late- 
 rite) 4 
 
 Jurassic Amador group 
 
 Greenstone 1 
 
 Depth 
 feet inches 
 
 285 
 280 
 
 2'.)0 
 
 * No core, description from driller's log. 
 
 HOLE 24-8 
 
 !>00 feet due S. of Hole 2.'i-2. Elevation 213 feet. 
 
 Eocene lone formation 
 Upper lone member 
 
 (Jreen sands and clay * 235 
 
 B.uff clay 
 
 Gray clay 
 
 Gray clayey silt with biotite 4 
 
 Xo core 1 
 
 Jurassic Amador group 
 
 Fresh greenstone 
 
 Thickness 
 feet inches 
 
 Depth 
 
 feet inches 
 
 10 
 11 
 
 235 
 235 
 23(i 
 240 
 242 
 
 243 
 
 10 
 9 
 
 11 
 5 
 
 * No core, description from driller's log. 
 
 HOLE 24-9 
 
 'lO feet ir. of llfiit eaxt property line, lO.lO feet K. of Hart south 
 property line, and 1000 feet iS'. of hole 2Jf-]. Elevation 273 feet. 
 
 Eocene lone formation 
 Upper lone member 
 
 Sand* 2(1 
 
 (ireen clay * 19 
 
 Lower lone member 
 
 Gray clay gradually becoming lighter 
 
 in color * 30 
 
 Gray clay * (! 
 
 White clay with some sand and buff 
 
 .stains. '(I'el)ble bed at 81' 4".)___ 4 
 White clay with some sand and red 
 
 stains 4 
 
 Red and white banded clay with 
 
 some silt 2 
 
 I'ink and white silty clay 
 
 Pink silty clay with red spots :! 
 
 I'ink sandy clay 1 
 
 White argillaceous siltstone with 
 
 iron nodules 1 
 
 White argillaceous fine-grained sand- 
 stone 3 
 
 Buff argillaceous fine-grained sand- 
 stone 1 
 
 White argillaceo\is siltstone with 
 
 some yellow stains 
 
 I'.uff argillaceous siltstone 
 
 White argillaceous fine-grained 
 
 sandstone 2 
 
 Pinkish l)uff clay 1 
 
 Banded red, yellow, and white clay. .'» 
 
 Reddi.sh clay 2 
 
 Red and white sandy clay 1 
 
 Yellowish argillaceous sandstone 1 
 
 Yellow ;irgillace<>us sandstone with 
 
 iron nodules 
 
 Pink silty clay with white spots 1 
 
 Jurassic Amador group 
 
 I'ink to red gritty clay (residual) __ 2 
 
 Green gritty da.v (residual) 1 
 
 A\'eathere<l greenstone , 
 
 Fresh greenstone 1 
 
 Thickness 
 feet inches 
 
 Depth 
 feet inches 
 
 26 
 45 
 
 
 <•> 
 81 
 
 
 
 85 
 
 
 
 89 
 
 
 10 
 
 7 
 
 91 
 91 
 95 
 
 10 
 
 5 
 
 7 
 
 97 
 
 98 
 
 101 
 
 102 
 
 
 1 
 10 
 
 108 
 lOS 
 
 1 
 11 
 
 1 
 
 n 
 1(1 
 
 111 
 112 
 11.-. 
 117 
 IIS 
 120 
 
 S 
 (i 
 
 
 
 121 
 122 
 
 
 *> 
 
 10 
 
 124 
 125 
 125 
 127 
 
 o 
 
 * No core, description from driller's log. 
 
loNE Formation, Buena Vista Area 
 
 37 
 
 HOLE B.V. 1 
 
 Approjimutely 900 feet S. l.C W. of the power plant at the liuena 
 Vista wax plant. Elevation 362 feet. 
 
 Thickness Depth 
 
 Recent soil feet inches feet inches 
 
 Red soil with cobbles 2 2 
 
 Eocene lone formation 
 Upper lone member 
 
 I'alp-green clay l-*? C 35 fi 
 
 dray to Kreenish-grny loose sand 8 23 (i 
 
 Yellowish-gray sand 1 24 
 
 Grav-white sand 2 26 G 
 
 Huff sand 16 28 
 
 Creenish-gray clayey sand 8 36 
 
 (Jreenish-gray clay 4 40 
 
 (Jreenish-gray clayey sand 4 44, 
 
 I.ight-gray loose sand 15 50 
 
 Tan coarse-grained loose sand 2 61 
 
 Huff coarse-grained loose sand 6 61 6 
 
 Tan clayey sand 2 6 64 
 
 Blue-gray clayey sand 1 65 
 
 HOLE B.V. 2 
 
 On top of small hill approximately IHOO feet «S'. 7.7° W. of the power 
 
 plant at the Buena Vista wax plant. Elevation 392 feet. 
 
 Thickness Depth 
 
 Eocene lone formation feet inches feet inches 
 Upper lone member 
 
 Not cored but included gray silt- 
 stone, chocolate-colored clay, and 
 
 .some buff-stained white sand 44 6 44 6 
 
 Tan to white clayey .sand 4 11 49 5 
 
 Loose grayish sand 6 7 56 
 
 (Irayish white clayey sand 3 ,59 
 
 I>oose grayish sand 6 65 
 
 Grayish-white clayey sand 1 66 
 
 I-oose grayish sand 4 70 
 
 Tan sand with sotne clay 7 77 
 
 Tan sand with pebl)les and some clay 1 78 
 
 Buff sandy clay to clay 2 80 
 
 HOLE B.V. 3 
 
 On crest of ridge ahout 900 feet Si. 33" W. of the poirer plant at the 
 liuena ri.t/o wax plant. Elevation Jf 20 feet. 
 
 Thickness Depth 
 
 Eocene lone formation feet inches feet inches 
 
 Upper lone member 
 
 Buff, brown, and tan clays and sands 20 20 
 
 Buff, greenish-tan, and lavender 
 
 clays and sands 50 70 
 
 Ferruginous sand 1 71 
 
 Light-gray sand with some pebbles 29 100 
 
 .Light-gray quartz conglomerate 1 101 
 
 Greenish-gray clay 9 110 
 
 HOLE B.V. 4-A 
 
 On top of .imall hill ahout 2>,00 feet ^\' . of the power plant at the 
 liuena Vista wax plant. Elevation 3//! feet. 
 
 Approximate Approximate 
 Eocene lone formation thickness depth 
 
 Upper lone member /f' inches feet inches 
 
 Grayish-white sand .30 30 
 
 Brown sand 1 ,31 
 
 Buff to greenish silty clay 39 70 
 
 HOLE B.V. 4-B 
 
 On crest of ridge ahout (I.IO feet »S'. 7° W. of the power plant at the 
 liuena Vista tcax plant. Elevation 380 feet. 
 
 Thickness Depth 
 
 Quaternary terrace gravel feet inches feet inches 
 
 Brown conglomerate, large cobbles 5 5 
 
 Eocene lone formation 
 
 Upper lone member 
 
 Greenish-buff sandy clay 3 30 8 10 
 
 J-ight-gray sand 112 20 
 
 Linxmite-stained sand 20 
 
 Light greenish-gray sand 9 29 
 
 Greenish-gniy to greenish-buff clay- 10 6 40 
 Light greenish-gray sand with some 
 
 clay 6 46 
 
 Light grayish-tan sand 3 49 
 
 Light gray quartz conglomerate with 
 jiebbles less than 1 inch in diam- 
 eter 2 .51 
 
 Hard limonite-rich streak 2 51 2 
 
 Greenish-gray cl;iy 7 •"> .58 .5 
 
 (Jreenish-brown clay 11 59 6 
 
 Gray-green clay 4 6 64 
 
 Greenish-gray clay with rust-colored 
 
 stains 2 60 
 
 HOLE B.V. 5 
 
 In loir saddle on crest of same ridge as Hole li.V. 1 ahout 1500 feet S. 
 .'i.i" ir. of the power house at the liuena ^'isla wax plant. Elevation 
 .',17 feet. 
 
 Eocene lone formation Thickness ^Depth 
 
 Upper lone member /<"«' inches feet inches 
 
 Buff, greenish-buff, and brown sand 
 
 and silt 19 4 19 4 
 
 fJreenish-white sand 5 8 25 
 
 Buff-brown clayey sand 3 28 
 
 Buff, brown, and light-gray clay 
 
 with some sand lenses .' 6 .34 
 
 Light-brown clay 3 37 
 
 Brown clay 1 38 
 
 Light blue-gray clay 4 42 
 
 Hard light-brown sandy clay 16 43 6 
 
 Hard light-gray sandy clay 2 6 46 
 
 White clayey sand 4 .50 
 
 Buff sand 3 .50 3 
 
 White clayey sand 4 5 54 8 
 
 White sand 11 4 66 
 
 Fine-grained conglomerate with 
 nianv black pebbles and white 
 
 sand matrix 14 9 80 9 
 
 Tan sandy clay with limonite con- 
 cretions, a lense of fine-grained 
 
 conglomerate at about 83 feet 4 .3 85 
 
 Buff and tan sandy clay grading to 
 
 greenish color toward the base 1.3 98 
 
 Light gray-green clay 2 100 
 
 (Jray-green clay 2 8 102 8 
 
 HOLE K-10 
 
 At present site of Kaolin-Fije clay pit ahout 12.') feet northeast of 
 Calaveras Cement Company southwest property line and 250 feet 
 northwest of stream. Elevation ■i5t< feet. 
 
 Quaternary terrace gravel Thickness 
 
 and alluvium /'■'' '■"'•''<■« 
 
 ("oarse reddish-brown conglomerate 10 
 
 Eocene lone formation 
 Lower lone member 
 
 White clayey sand stained yellow for 
 
 about 2 feet at bottom 22 6 
 
 Dark-grav clayey sand and lignite 
 
 below .32 6 
 
 Depth 
 feet inches 
 
 10 
 
 32 
 
38 
 
 Special Report 19 
 
 HOLE K-11 
 
 About loO feet E. of K-10. Elevation 3/,.J feet. 
 
 Eocene lone formation Thickness Depth 
 
 Lower lone member /^<^* inches feet inches 
 
 AVIiite clayey sand with yellow stain 
 
 for about 2 feet at bottom 25 25 
 
 Dark-gray clayey sand and lignite 
 
 below 25 
 
 HOLE K-12 
 
 About 300 feet E. of K-10. Elevation 360 feet 
 
 Quaternary terrace gravel Thickness 
 
 and alluvium feet inches 
 
 Keddish-brown conglomerate 18 
 
 Eocene lone formation 
 Lower lone member 
 
 White clayey sand, stained yellow 
 
 for about 2 feet at bottom IG 
 
 Dark-gray clayey sand and lignite 
 
 below 34 
 
 Depth 
 feet inches 
 
 18 
 
 34 
 
 Chemical analyses * 
 
 ' Analyses released for publication on condition that name of analyst remain confidential. 
 
 
 
 
 
 
 
 Analysis 
 
 
 
 1 
 
 
 Analysis 
 number 
 
 Hole 
 num- 
 ber 
 
 Depth in 
 feet 
 
 
 
 
 
 
 
 1 
 
 Formation 
 
 
 
 
 
 Loss on 
 
 Free 
 
 Lithologic description 1 
 
 
 
 
 
 AljOa 
 
 Fes03 
 
 SiOs 
 
 TiOj 
 
 ignition 
 
 Si02 
 
 1 
 
 Greenstone 
 
 7-1-0 
 
 7-1 
 
 263-264 
 
 33.30 
 
 11.60 
 
 45.80 
 
 .79 
 
 8.51 
 
 1.29 
 
 Highly altered greenstone. J 
 
 
 24-lA 
 
 24-1 
 
 88 
 
 20.80 
 
 17.00 
 
 39.00 
 
 .84 
 
 8.1 
 
 
 Greenstone. fl 
 
 Pre- lone Eocene (?) sediment 
 
 7-1 -M 
 
 7-1 
 
 232-233 
 
 24.93 
 
 5.00 
 
 61.88 
 
 1.02 
 
 7.17 
 
 6.57 
 
 Gray argillaceous siltstone. 1 
 f 235 '-235 ' 3 " Gray argillaceous siltstone. T 
 l235' 3 "-235' 9" Dark-gray carbonaceous argilla- 
 
 " 
 
 7-1-N 
 
 7-1 
 
 235-236 
 
 27.43 
 
 3.55 
 
 59.51 
 
 1.10 
 
 8.41 
 
 2.74 
 
 ) ceous siltstone. 
 
 [235 ' 9 ' '-236 ' Very light-brown argillaceous siltstone. 
 
 " 
 
 18-1-Ll 
 
 18-1 
 
 311-313 
 
 22.58 
 
 5.45 
 
 65.91 
 
 .34 
 
 5.72 
 
 2:76 
 
 Reddish-buff silty clay with some pebbles. 
 
 " 
 
 18-1-01 
 
 18-1 
 
 373-374 
 
 24.34 
 
 3.80 
 
 65.37 
 
 .47 
 
 6.02 
 
 4.26 
 
 Greenish-white sandy clay with yellow stains. 
 
 " 
 
 18-2-F 
 
 18-2 
 
 253-254 
 
 26.18 
 
 7.15 
 
 55.71 
 
 1.18 
 
 9.78 
 
 4.91 
 
 Buff-brown silty clay. 
 
 lone formation, Lower lone 
 
 
 
 
 
 
 
 
 
 
 
 member 
 
 7-1 -A 
 
 7-1 
 
 35-36 
 
 23.37 
 
 1.80 
 
 64.99 
 
 1.81 
 
 8.03 
 
 3.34 
 
 Pale-brown clay with yellow stains. 
 
 " 
 
 7-1 -B 
 
 7-1 
 
 41-42 
 
 24.26 
 
 1.75 
 
 63.90 
 
 1.66 
 
 8.43 
 
 1.92 
 
 Pale-brown clay with yellow stains. 
 
 " 
 
 7-1-D 
 
 7-1 
 
 139-140 
 
 28.17 
 
 6.00 
 
 56.15 
 
 1.22 
 
 8.46 
 
 3.90 
 
 Red and buff clay with pebbles. 
 
 " 
 
 7-1-E 
 
 7-1 
 
 215-216 
 
 27.34 
 
 7.90 
 
 52.09 
 
 1.16 
 
 11.51 
 
 4.42 
 
 Buff silty clay with siderite nodules. 
 
 " 
 
 7-1 -F 
 
 7-1 
 
 220-221 
 
 24.03 
 
 13.40 
 
 48.34 
 
 1.20 
 
 13.03 
 
 3.11 
 
 Light-buff and red mottled sandy clay. 
 
 " 
 
 7-1-G 
 
 7-1 
 
 222-223 
 
 25.97 
 
 10.80 
 
 51.51 
 
 1.14 
 
 10.58 
 
 5.36 
 
 Red sandy clay, .some buff mottling. 
 
 " 
 
 7-1-H 
 
 7-1 
 
 224-225 
 
 25.77 
 
 14.55 
 
 46.35 
 
 1.26 
 
 12.07 
 
 5.41 
 
 Red sandy clay, some buff mottling. 
 
 " 
 
 7-1 -J 
 
 7-1 
 
 226-227 
 
 24.45 
 
 21.30 
 
 38.41 
 
 1.22 
 
 14.62 
 
 1.68 
 
 Red sandy clay, some buff mottling. 
 
 " 
 
 7-1-K 
 
 7-1 
 
 228-229 
 
 27.79 
 
 12.35 
 
 47.04 
 
 1.20 
 
 11.62 
 
 .91 
 
 Red and buff mottled clay. 
 
 " 
 
 7-1-L 
 
 7-1 
 
 230-231 
 
 29.54 
 
 5.15 
 
 55.01 
 
 1.22 
 
 9.08 
 
 3.16 
 
 Buff clay. 
 
 " 
 
 13-2-A 
 
 13-2 
 
 169-169.5 
 
 31.95 
 
 18.55 
 
 34.. 52 
 
 2.45 
 
 12.. 53 
 
 
 Buff to red clay with a little sand. 
 
 " 
 
 18-1-A 
 
 18-1 
 
 276-277 
 
 27.48 
 
 6.40 
 
 56.86 
 
 .85 
 
 8.41 
 
 3.95 
 
 Red sandy clay with buff spots. 
 
 " 
 
 18-1-B 
 
 18-1 
 
 277-278 
 
 29.62 
 
 6.70 
 
 55.13 
 
 .79 
 
 7.76 
 
 9.10 
 
 Red sandy clay with buff spots. 
 
 " 
 
 18-1-C 
 
 18-1 
 
 278-279 
 
 24.73 
 
 4.10 
 
 64.64 
 
 .67 
 
 5.86 
 
 8.42 
 
 Red sandy clay with buff spots. 
 
 u 
 
 18-1-D 
 
 18-1 
 
 279-280 
 
 29.30 
 
 5.40 
 
 57.86 
 
 .64 
 
 6.80 
 
 11.10 
 
 Red sandy clay with buff spots. 
 
 
 18-1-E 
 
 18-1 
 
 280-281 
 
 27.20 
 
 6.10 
 
 58.09 
 
 .67 
 
 7.94 
 
 6.10 
 
 280'-280' 5" Red sandy clay with buff spots. 
 280' 5"-28r Red and buff clay with some silt. 
 
 " 
 
 18-1-F 
 
 18-1 
 
 281-282 
 
 27.55 
 
 7.15 
 
 56.29 
 
 .67 
 
 8.34 
 
 6.21 
 
 Red and buff clay with some silt. 
 
 " 
 
 18-1-G 
 
 18-1 
 
 282-283 
 
 26.54 
 
 7.40 
 
 56.49 
 
 .75 
 
 8.82 
 
 4.73 
 
 Red and buff clay with some silt. 
 
 " 
 
 18-1-H 
 
 18-1 
 
 283-284 
 
 29.09 
 
 6.50 
 
 55.82 
 
 .64 
 
 7.95 
 
 6.93 
 
 Red and buff clay with some silt. 
 
 " 
 
 18-1-J 
 
 18-1 
 
 284-285 
 
 30.15 
 
 5.05 
 
 57.78 
 
 .53 
 
 6.49 
 
 11.93 
 
 Red and buff clay with some silt. 
 
 " 
 
 18-1-K 
 
 18-1 
 
 285-286 
 
 24.62 
 
 9.05 
 
 57.57 
 
 .83 
 
 7.93 
 
 3.45 
 
 Red, yellow, and white mottled sandy clay. 
 
 " 
 
 18-1-L 
 
 18-1 
 
 286-287 
 
 25.42 
 
 6.70 
 
 59.51 
 
 .67 
 
 7.70 
 
 4.14 
 
 Red, yellow, and white mottled sandy clay. 
 
 " 
 
 18-1-M 
 
 18-1 
 
 287-288 
 
 26.27 
 
 5.70 
 
 59 . 85 
 
 ..56 
 
 7.62 
 
 5.74 
 
 Red, yellow, and white mottled sandy clay. 
 
 
 18-1-N 
 
 18-1 
 
 288-289 
 
 26.95 
 
 7.70 
 
 55.92 
 
 ..53 
 
 8.90 
 
 7.96 
 
 288'-288' 2" Red, yellow, and white mottled sandy 
 
 clay. 
 288' 2 "-289' White sandy clay with yellow stains 
 
 and iron nodules. 
 
 " 
 
 18-1-0 
 
 18-1 
 
 289-290 
 
 26.06 
 
 5.35 
 
 60.63 
 
 .45 
 
 7.51 
 
 5.23 
 
 White sandy clay with yellow stains and iron 
 
 nodules. 
 Dark-yellow sandy clay with red and white areas. 
 
 « 
 
 18-1-P 
 
 18-1 
 
 290-291 
 
 21.32 
 
 9.75 
 
 61.. 56 
 
 .60 
 
 6.77 
 
 4.16 
 
 " 
 
 18-1-Q 
 
 18-1 
 
 291-292 
 
 23.69 
 
 10.70 
 
 57.70 
 
 .64 
 
 7.27 
 
 5.06 
 
 Dark-yellow sandy clay with red and white areas. 
 
 " 
 
 18-1-R 
 
 18-1 
 
 292-293 
 
 24.62 
 
 9.45 
 
 58.47 
 
 .60 
 
 6.86 
 
 6.64 
 
 Dark-yellow sandy clay with red and white areas. 
 
 " 
 
 18-1-S 
 
 18-1 
 
 293-294 
 
 25.66 
 
 6.95 
 
 59 . 1 5 
 
 .56 
 
 7.68 
 
 5.54 
 
 Dark-yellow sandy clay with red and white areas. 
 
 " 
 
 18-1-T 
 
 18-1 
 
 294-295 
 
 27.79 
 
 3.30 
 
 63.03 
 
 .49 
 
 5.39 
 
 11.97 
 
 Yellow and white argillaceous siltstone. 
 
 " 
 
 18-1-U 
 
 18-1 
 
 295-296 
 
 26.53 
 
 1.70 
 
 64.96 
 
 .53 
 
 6.28 
 
 7.75 
 
 Weathered conglomerate; various colored pebbles 
 in pink to brown matrix. 
 
 " 
 
 18-1-V 
 
 18-1 
 
 296-297 
 
 27.81 
 
 1.25 
 
 64.18 
 
 .51 
 
 6.25 
 
 8.61 
 
 Weathered conglomerate; various colored pebbles 
 in pink to brown matrix. 
 
 " 
 
 18-1-W 
 
 18-1 
 
 297-298 
 
 29.96 
 
 2.05 
 
 58.99 
 
 .51 
 
 8.49 
 
 5.23 
 
 Weathered conglomerate; various colored pebbles 
 in pink to white matrix. 
 
 " 
 
 18-1-X 
 
 18-1 
 
 298-299 
 
 30.83 
 
 2.65 
 
 56.75 
 
 .89 
 
 8.88 
 
 5.55 
 
 Weathered conglomerate; various colored pebbles 
 in white matrix. 
 
 " 
 
 18-1-Y 
 
 18-1 
 
 299-300 
 
 30.20 
 
 2.15 
 
 58.31 
 
 .73 
 
 8.61 
 
 5.10 
 
 Weathered conglomerate; various colored pebbles 
 in white matrix. 
 
 
 18-1-Z 
 
 18-1 
 
 300-301 
 
 31.47 
 
 1.60 
 
 58.28 
 
 .71 
 
 7.94 
 
 8.77 
 
 Weathered conglomerate; various colored pebbles 
 in white matrix. 
 
loNE POKMATION, BUENA VlSTA ArKA 
 
 39 
 
 Cliriniral analyses * — continued 
 
 Formation 
 
 Lower lone member — cont. 
 
 I 
 
 (?) 
 
 ppcr lone member (?) 
 " (7) 
 
 Analysis 
 number 
 
 18-1-Al 
 
 18-1-Bl 
 
 18-1-Cl 
 18-1-DI 
 18-1-EI 
 
 18 1-n 
 
 I8-1-C;i 
 
 I8-1-III 
 
 18-l-.n 
 
 18-1-Kl 
 
 I8-I-MI 
 
 18-1-Nl 
 
 18-2- A 
 
 18-2-B 
 24-2-A 
 24-2-B 
 24 -3- A 
 24-3-B 
 24-3-C 
 
 24-3-D 
 
 24-3-E 
 
 24-3-K 
 
 24-3-G 
 
 24-3-It 
 24-3-J 
 
 24-3-K 
 
 24-3-L 
 24 -5- A 
 24-5-B 
 24-5-C 
 
 24-5-D 
 24-5-E 
 24-5-F 
 
 24-5-t; 
 
 24-fi-C; 
 
 24-6- D 
 
 24-6-E 
 
 24-6- F 
 
 24-6 (; 
 24-6-H 
 
 24-6 -J 
 
 24-6-K 
 
 24-6 L 
 
 24 6M 
 
 24 -6- A 
 24-6-B 
 
 Hole 
 num- 
 ber 
 
 18-1 
 
 18-1 
 
 18-1 
 18-1 
 18-1 
 
 18-1 
 18-1 
 18-1 
 18-1 
 18-1 
 18-1 
 18-1 
 18-2 
 
 18-2 
 24-2 
 24-2 
 24-3 
 24-3 
 24-3 
 
 24-3 
 
 24-3 
 
 24-3 
 
 24-3 
 
 24-3 
 24-3 
 
 24-3 
 
 24-3 
 24 -.■) 
 24-3 
 24-5 
 
 24-5 
 24-5 
 24-5 
 
 24 -5 
 
 24-6 
 
 24-6 
 
 24-6 
 
 24-6 
 
 24-6 
 24-6 
 
 24-6 
 
 24-6 
 
 24-6 
 
 24-6 
 
 24 6 
 24 6 
 
 Depth in 
 feet 
 
 301-302 
 
 302-303 
 
 303-304 
 304-305 
 305-306 
 
 306-307 
 307-308 
 308-309 
 309-310 
 310-311 
 1.54-155 
 187-188 
 228-229 
 
 234-235 
 164-165 
 167-168 
 124-125 
 129-130 
 144-145 
 
 145-146 
 
 156-157 
 
 159-160 
 
 174-175 
 
 178-179 
 180-181 
 
 202-203 
 
 210-211 
 5-6 
 10-11 
 15-16 
 
 20-21 
 31-32 
 40-41 
 
 45 46 
 
 176-177 
 
 178-179 
 
 180 181 
 
 182 183 
 
 184-194 
 196-197 
 
 199 200 
 
 201 202 
 
 204 214 
 
 218-219 
 
 114-115 
 157-158 
 
 Analysis 
 
 AhOj 
 
 26.44 
 
 26.50 
 
 25.. 54 
 24.91 
 26.52 
 
 23 . 72 
 23.06 
 24.23 
 22.28 
 23.31 
 .36.06 
 28.93 
 25.76 
 
 23.19 
 31.52 
 22.63 
 38.83 
 39.05 
 34.85 
 
 32.90 
 
 32.66 
 
 27.60 
 
 32.98 
 
 30.16 
 27.80 
 
 27.28 
 
 26.88 
 28.05 
 31.23 
 32.05 
 
 .34.97 
 31.67 
 29.39 
 
 28.71 
 
 28.00 
 
 28.73 
 
 30. 14 
 
 23.91 
 
 25 . 76 
 30.. 53 
 
 29.72 
 
 27.44 
 
 30.10 
 
 27 . 55 
 
 29.49 
 29.10 
 
 FesOa 
 
 1.25 
 
 1.20 
 
 1.40 
 1.40 
 3.90 
 
 4.95 
 4.70 
 4.65 
 4.30 
 4.. 50 
 2.60 
 8.75 
 14.25 
 
 18. .50 
 1.60 
 3.75 
 1.60 
 1.90 
 
 10.45 
 
 13.85 
 
 14.95 
 
 27.85 
 
 14.70 
 
 18.75 
 19.30 
 
 21.10 
 
 20.20 
 24 . 05 
 17.85 
 14.85 
 
 11.25 
 17. 50 
 21.75 
 
 12.45 
 
 21,80 
 
 22.75 
 
 17.. 55 
 
 25.75 
 
 26.30 
 17.. 50 
 
 19.10 
 
 23 . 75 
 
 16.20 
 
 20.65 
 
 3.75 
 10.15 
 
 SiOj 
 
 TiOj 
 
 65.03 
 
 64.49 
 
 66.07 
 6(5.89 
 62 . 45 
 
 64.58 
 65.91 
 65. 15 
 67 . 65 
 66.03 
 45.77 
 47.67 
 47.37 
 
 45.. 58 
 54.81 
 64.40 
 43 . 34 
 42.70 
 37.31 
 
 35.31 
 
 35.15 
 
 27.46 
 
 39.70 
 
 37.82 
 40.86 
 
 38.14 
 
 40.08 
 33.05 
 36.00 
 37 . 52 
 
 39.10 
 35.93 
 34.95 
 
 46 . .56 
 
 36.13 
 
 34.68 
 
 36.98 
 
 32.18 
 
 30.82 
 37.12 
 
 37 . 39 
 
 34 . 92 
 
 39.88 
 
 37.85 
 
 56.76 
 51.53 
 
 ..56 
 
 .56 
 
 ..58 
 
 .49 
 
 .34 
 
 2.05 
 
 1.72 
 
 1.18 
 
 1.24 
 .42 
 .91 
 2.71 
 2. 54 
 2.59 
 
 2.57 
 
 3.03 
 
 2.45 
 
 1.62 
 
 1 .95 
 1.45 
 
 1.38 
 
 1.38 
 2.19 
 2.00 
 1 .66 
 
 .98 
 1.60 
 1.51 
 
 1.12 
 
 2.37 
 
 2.45 
 
 1.81 
 
 1.62 
 
 2.42 
 1.38 
 
 1 . 54 
 
 2. 19 
 1.84 
 2.12 
 
 .85 
 1.20 
 
 Loss on 
 ignition 
 
 6.77 
 
 7.23 
 
 6.46 
 6.. 36 
 6.62 
 
 6.19 
 
 5.77 
 
 5.39 
 
 5.28 
 
 5.82 
 
 13.52 
 
 12.93 
 
 11.44 
 
 11.49 
 11.65 
 8.31 
 13.. 52 
 13.81 
 14.80 
 
 15.37 
 
 14.21 
 
 14.64 
 
 10.94 
 
 11.32 
 10.59 
 
 12.10 
 
 11.46 
 12.66 
 12.92 
 13.92 
 
 13.70 
 13.30 
 12.40 
 
 11.16 
 
 11.70 
 
 11.39 
 
 13.. 52 
 
 16.54 
 
 14.70 
 13.47 
 
 12.25 
 
 11.70 
 
 1 1 . 98 
 
 11.83 
 
 9.15 
 8.02 
 
 Free 
 SiOj 
 
 6.04 
 
 5.96 
 
 6.49 
 5.66 
 6.22 
 
 5.55 
 4.35 
 6.95 
 5.57 
 4.28 
 
 2.23 
 1.89 
 
 1.35 
 1.21 
 1.02 
 
 4.25 
 .85 
 
 Litiiologic description 
 
 .64 
 
 .63 
 
 Weathered conglomerate; various colored pebbles 
 in white matrix. 
 
 White conglomerate with spots of carbonaceous 
 material. 
 
 White clay with sand grains, some pale-green areas. 
 
 White clay with sand grains, some pale-green areas. 
 
 305'-305' 3" White clay with sand grains, some 
 pale green areas. 
 
 305' 3"-306' Deep red clay with quartz pebbles, 
 white patches. 
 
 Deep red clay with quartz pebbles, white patches. 
 
 Deep red clay with quartz pebbles, white patches. 
 
 Deep red clay with quartz pebbles, white patches. 
 
 Deep red clay with ijuartz pebbles, white i)atches. 
 
 Deep red clay with quartz pebbles, white patches. 
 
 Light-gray clay. 
 
 Cream- colored clay with siderite pellets. 
 
 Red and buff mottled clay with some sand and iron 
 nodules. 
 
 Dark-red clay with iron nodules. 
 
 White clay, conchoidal fracture. 
 
 White clay with some silt. 
 
 White clay with some sand grains. 
 
 White silty clay with some yellow stain. 
 
 Reddish- buff and gray mottled clay, some iron 
 nodules (siderite?) (reworked laterite). 
 
 Reddish-buff and gray mottled clay, sonic iron 
 nodules (siderite?) (reworked laterite). 
 
 Red and white mottled clay with specks of iron 
 oxides, (reworked laterite). . 
 
 Red and white niuttird clay with abundant iron 
 nodules (.siderite?) (reworked laterite). 
 
 White clay with some red clay, mottled, (reworked 
 laterite). 
 
 Yellow and red clay (reworked laterite). 
 
 Dark bi'ff and purple mottled clay (reworked 
 laterite). 
 
 Yellowish claylike material with red stain, white 
 spots, (reworked laterite). 
 
 Rtd and white claylike material (reworked laterite). 
 
 Red and buff mottled clay (reworked laterite). 
 
 Red and huff mottled clay (reworke<l laterite). 
 
 Red, buff, and pur|)le mottled clay (reworked 
 laterite). 
 
 Red and buff mottled clay (reworked laterite). 
 
 Red clay with some mottling (reworked laterite). 
 
 Red. yellow, and purple mottled clay with some 
 sand grains (reworked laterite). 
 
 Red. yellow, and purple mottled clay with some 
 .sand grains, (reworked laterite). 
 
 Red, white, and buff coarsely mottled clay (re- 
 worked laterite). 
 
 Red. white, and buff coarsely mottled clay (re- 
 worked laterite). 
 
 Red. white, and buff coarsely mottled clay (re- 
 worked laterite). 
 
 Red, white, and buff coarsely mottled clay (re- 
 worked laterite). 
 
 Red and buff mottled clay (reworked laterite). 
 
 Red, white, and buff mottled clay (reworked 
 laterite). 
 
 Red clay with small white patches (reworked 
 laterite). 
 
 Red clay 
 laterite). 
 
 Red clay 
 laterite). 
 
 Red clay with small white patches (reworked or 
 residual laterite). 
 
 Greenish-buff silty clay. 
 
 Light brownish-buff clay with biotite. 
 
 ith small white patches (reworked 
 with small white patches (reworked 
 
 Analyses rclea.sed for publication on condition that name of analyst remain confldenliiil. 
 
 S350 2-52 2M 
 
 printed in caliiornia stail printing otricE 
 
DIVISION OF MINES 
 OLAF P. JENKINS, CHIEF 
 
 STATE OF CALIFORNIA 
 DEPARTMENT OF NATURAL RESOURCES 
 
 SPECIAL REPORT 19 
 PLATE I 
 
 
 ] area warked 
 
 
 Hi 
 
 ?7^ 
 
 £^ 
 
 
 TVS 
 
 bs, Is, brs, hts 
 
 rhy 
 
 c-rk 
 
 gsc, qc, grc 
 
 eg 
 
 ws 
 
 gis, gc, ggrc 
 ggrs, gbc, gbs 
 
 ws, wsc, hws 
 
 wc, grc 
 
 be, bsc 
 
 bs, Is, brs 
 
 eg, wcg, grcg,fcg 
 
 Tli-UfTli-l 
 wc, grc, w-ffc 
 
 be, y+ w 
 gr+bre 
 
 brtfc, btfc, be, 
 ye, bre, re 
 
 lot. 
 brcg, fcg 
 
 EXPLANATION 
 
 Alluvium 
 Terroees 
 
 Undifferentiated 
 
 Buff, ton, brown sends, hord Ion sond 
 
 Rtiyolite ond rhyolite luff 
 
 Cloy rock 
 
 Green sandy cloy, groy and green cloys 
 
 Conglomerate 
 
 White sond 
 
 Undifferentioted 
 
 Grecn-groy, green-buff, green-Ion sonds 8 cloys 
 
 While sonds a sondy cloy, hard white sond 
 
 White, groy clays 
 
 Buff cloy a sandy cloys 
 
 Buff, ton, brown sond 
 
 Conglomerotes, white, gray a ferruginous 
 
 Undifferentioted 
 
 White, gray ond whrte and ferruginous cloys 
 
 White sond ond sandy clays 
 
 Buff, yellow a white, groy a brown cloys 
 
 Brown sondy cloy 
 
 Buff, brown, a ferruginous sonds 
 
 Yellow, buff, brown, ferruginous a red cloys 
 
 Loterite 
 
 Brown ond ferruginous conglomerates 
 
 e 
 
 >^3 
 
 E Q- 
 
 e 
 
 Jurassic fl^^l^/' Jir 
 
 o 
 
 Greenstone ond slate 
 
 Confoet, dashed where uncertoii 
 Contoet inferred 
 
 Cloy pit 
 
 Mine or quorry 
 
 Gold plocer operation 
 
 Drill hole 
 
 Moriposo slote a 
 Amador group 
 
 Bose mop from Bureou of Reelomotion 
 lone Reservoir Area, Sheet 2, 1946 
 
 Geologic mopping 1950 to 1951 
 
 GEOLOGIC MAP OF THE BUENA VISTA AREA, AMADOR COUNTY, CALIFORNIA 
 
 By Mort D. Turner 
 
 SCALE 
 2000 
 
SPEClfll. flEPORT I 
 
LOG OF HOLE 18-1 BUENA VISTfl AREA, AMADOR COUNTY, CALIFORNIA