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 1-A DECEMBER 1950 SIERRA BLANCA LIMESTONE IN SANTA BARBARA COUNTY, CALIFORNIA By GEORGE W. WALKER U. S. Department of the Interior, Geological Survey f 'BRARY UNIVEk.. . Y OK CALIFORNIA DAVIS SIERRA BLANCA LIMESTONE IN SANTA BARBARA COUNTY, CALIFORNIA* By George W. Walker * * OUTLINE OF REPORT Page ABSTRACT 8 INTRODUCTION .3 Acknowledgments 3 Location and accessibility 3 Topography and drainage 3 GENERAL GEOLOGY 3 SIERRA BLANCA LIMESTONE 4 Lithology and chemical composition 4 Economic evaluation 5 Illustrations Plate 1. Reconnaissance geologic map of part of the upper Santa Ynez River drainage basin, showing distribution of the Sierra Blanca limestone, Santa Barbara County, California 4-5 ABSTRACT Large bodies of pure and massive limestone crop out in the San Rafael Mountains, Santa Barbara County, California. Reconnaissance geologic mapping and a few chemical analyses of the limestone indicate large reserves of commercial-grade rock, but it has not been quarried because of the remoteness of the area, and because the potential value of the limestone is little known. The limestone bodies are faulted and folded seg- ments of the Sierra Blanca limestone, 1 which in this area is the basal member of a thick, marine, sedimentary section of Eocene age. Two widely separated groups of limestone outcrops are found in the map area ; the southern group occurring along the Santa Ynez River and Blue Can- yon and the northern group near the headwaters of Indian Creek. In the southern area the limestone ranges in thick- ness from 15 or 20 feet along Blue Canyon to a maximum of 50 feet, but in the northern area it attains a thickness of nearly 250 feet. Much of the limestone contains more than 90 percent CaC0 3 . The highest-grade rock occurs in the areas where the limestone is thickest. INTRODUCTION Acknowledgments During the summer of 1947 a part of the area con- taining the Sierra Blanca limestone was mapped by the Stanford University class in field geology, using as a base the Santa Barbara, Carpinteria, Hildreth Peak, Little Pine Mountain, and Big Pine Mountain quadrangle maps. Adjoining areas were mapped in October and November of 1947, by Dr. A. C. Waters and the author, as part of an investigation of possible water supplies for the City of Santa Barbara. This mapping was financed by the Santa Barbara Foundation, and it is with their sanction that this report has been released for publication. In December 1948, G. W. Walker revisited the area to make more detailed studies of the limestone and to collect addi- tional samples for chemical analysis. The work in Decem- • Published by permission of the Director, U. S. Geological Sur- vey. Manuscript submitted for publication December 19 49. ** Geologist, U. S. Department of the Interior, Geological Survey. 1 Nelson, R. N., Geology of the hydrographic basin of the upper Santa Ynez River, California : California Univ., Dept. Geol. Sci., Bull., vol. 15, no. 10, pp. 327-396, 1925. ber 1948 was done by the U. S. Geological Survey in cooperation with the California State Division of Mines. Location and Accessibility The Sierra Blanca limestone crops out as elongate strips in the drainage basin of the upper Santa Ynez River, principally in the vicinity of Mono and Indian Creeks and Blue Canyon. The limestone occurs in two distinct localities, one about 7 miles and the other approx- imately 18 miles north of the City of Santa Barbara. The northernmost outcrops are located on the south flank of Big Pine Mountain. The thickest and most continuous masses of limestone mapped are in the Big Pine Mountain quadrangle ; thinner and less continuous masses of lime- stone occur in the Santa Barbara, Carpinteria, Hildreth Peak, and Little Pine Mountain quadrangles. Poor accessibility has been the major factor prevent- ing exploitation of the limestone. The general area can be reached only by winding, Forest Service mountain roads, which are impassable, or nearly so, after rain storms. The limestone reaches its maximum thickness and CaC03 content in the northern and most inaccessible part of the area, in the vicinity of Indian Creek. From established roads these limestone outcrops can be reached only by walking, either a distance of 8 miles up Indian Creek from Camuesa road or a distance of 1% miles along the trace of the limestone from Big Pine Mountain road. Owing to the brush cover and cliffs either means of access is difficult. Topography and Drainage The maximum relief in the area containing limestone exceeds 3,000 feet. Most of the area is characterized by the steep-sided canyons and comparatively sharp ridges that are common in the Transverse Ranges of California. Cliffs as much as 150 feet in height are not uncommon where massive beds of sandstone and limestone crop out on canyon walls. Massive beds and major structural fea- tures control most of the topography and drainage ; the most pronounced structural feature of the area is the Santa Ynez fault, which creates a topographic low along its course across the area. All streams in the area are tributary to the Santa Ynez River. Most of the streams, including the Santa Ynez River, are intermittent, but nearly all of them have underground flow during a large part of the year. GENERAL GEOLOGY The mapped area is on the boundary between the Coast Ranges and the Transverse Ranges of California. Within this area extensive outcrops of Sierra Blanca limestone have been identified. The rocks of the region are almost exclusively of sedimentary origin and range in age from Jurassic (?) to Miocene. These rocks have been folded into broad synclines and anticlines, and locally are considerably faulted. Recent stream and ter- race gravels present in the area have not been delineated on plate 1. The sedimentary section in this area is probably more than 50,000 feet thick, including rocks of the Jurassic ( ?) (3) Special Report 1-A Franciscan group of unknown thickness. At no one local- ity is this thickness exposed in a continuous sequence of beds; however, the steeply plunging Agua Caliente anticline, extending across the southern half of the area mapped, provides good exposures of most of the rocks of t lie stratigraphic column. Along the trace of the axial plane of the Agua Caliente anticline, approximately 37,000 feet of Cretaceous sedimentary rocks in fault contact with Jurassic (?) rocks, are unconformably overlain by nearly 7,000 feet of sandstones and shales of Eocene age. The basal bed of these sandstones and shales is a 5-foot to 10-foot calcareous sandstone, middle Eocene in age, and paleontologically the equivalent of the Sierra Blanca limestone. In addition, rocks of Oligocene and Miocene age with a maximum thickness of nearly 4,500 feet are present in the western part of the area. North of the Santa Ynez fault (pi. 1), most of the faults and folds strike northwest, parallel to the regional trend of the Coast Ranges. The east-striking Big; Pine fault is a notable exception to the general trend. South- ward the trend of the main structural features changes and near the Santa Ynez fault it is almost east, parallel- ing the Santa Ynez fault and the structures of the Trans- verse Ranges south of the fault. The major faults in the area, northward from the Santa Ynez River, are respectively, the Little Pine, the Hildreth, and the Big Pine faults. The rocks north of the Santa Ynez River are strongly folded, with numerous drag folds on the flanks of major anticlines and synclines and considerable crushed and broken rock in the axial regions. The most strongly developed fold is the Agua Caliente anticline, which can be traced from the east to the west edge of the mapped area. North of the Agua Caliente anticline the folds are broad whereas to the south the folds are tighter and many faults are characteristic. Nearly all folds maintain a constant eastward plunge, though local flattening and steepening of the axes are common. SIERRA BLANCA LIMESTONE Iii the mapped area the Sierra Blanca limestone occurs in two separate elongate bands which are approxi- mately 8 miles apart. The thickest and purest limestone, in the northern area adjacent to Indian Creek, is nearly 250 feet thick and contains as much as 98 percent CaC0 3 . The limestone of the southern area, near the Santa Ynez River, ranges in thickness from 15 or 20 feet to a maxi- mum of 50 feet and has a higher percentage of impurities than the limestone to the north. At the type locality 2 on Indian Creek in the northern area the Sierra Blanca limestone is snow white to gray and is composed of abundant calcareous algae, forami- nifera, other calcareous organisms, finely crystalline cal- cium carbonate, some clay, and small amounts of other adulterating materials. The fossils, Discocyclina psila Woodring, TubulosHum tfjnnense Gabb, Eogryphus tol- mani ynezensis Hertlein and Grant, and others, 3 indicate that the age of the Sierra Blanca limestone is middle Eocene. South and east of the type locality, the Sierra Blanca limestone shows little change in fossil content or type of impurities present, though a gradual increase 2 Nelson, R. N., op. cit. s Fossils identified by J. G. Marks, Stanford University, Califor- nia, 1947. in the proportion by weight of contaminating materials takes place. To the east of Agua Caliente Creek and to the south of the Santa Ynez fault within the mapped area, calcareous sandstone represents a lateral facies of the limestone. The Sierra Blanca limestone, wherever it crops out, rests unconformably on rocks of Cretaceous age, and is overlain conformably by a thick sequence of middle and upper Eocene sandstone and shale. Within the area covered by the reconnaissance geo- logic map (pi. 1) Sierra Blanca limestone has been found only to the north of the Santa Ynez fault and to the south of the Big Pine fault. Dark-gray shale with lenses and beds of very impure limestone containing Discocyclina occur south of the Santa Ynez fault, but these rocks have no economic importance. In the southern limestone area adjacent to the Santa Ynez fault the Sierra Blanca limestone is found along the south limb of a minor anticline exposed on the north wall of Blue Canyon. It also forms a nearly continuous belt around the western end of the small syncline crossing Mono Creek immediately north of the Santa Ynez River. In the area to the north, the limestone is found in the complexly folded Loma Pelona syncline. This syncline plunges east and in the axial region is complexly broken and folded into a series of small synclines and anticlines. The north limb of the Loma Pelona syncline has been cut off by the Big Pine fault. In most outcrops of the Sierra Blanca limestone, individual beds range in thickness from 4 inches up to 5 feet. Locally some of the thinner beds have been brec- ciated, especially along many of the bedding planes. In most places this broken material has been recemented by coarsely crystalline calcite and by caliche. The thicker beds of limestone are commonly massive and have not been brecciated. Jointing in the limestone is very irregular, but two sets of joints predominate. One set parallels the bedding, resulting in a platy structure in many outcrops. The other set is roughly normal to the bedding, though it apparently has no constant trend. Joints are spaced at intervals rang- ing from 1 inch to 2 inches in the thinner limestone beds to as much as 4 feet in the thicker beds. Locally, the less competent rocks immediately beneath the Sierra Blanca limestone have been sheared and crushed for distances of 10 to 20 feet from the con- tact. Scattered blocks of limestone, surrounded by the sheared sediments, occur in the zone of deformation, usually within a few feet of the main limestone beds. Lithology and Chemical Composition The Sierra Blanca limestone is composed largely of calcareous algae and foraminiferal remains. In many out- crops algae or clusters of algae are abundant and snow white and the surrounding carbonate material is gray or buff, giving the limestone a mottled appearance. In other outcrops the limestone is very fine-grained, and original textures cannot be resolved. Grains of quartz, feldspar, »;lauconite, and sparse rounded pebbles of chert and greenstone are found locally in the limestone. The pro- portion by weight of these impurities increases in rocks toward the south and east edges of the mapped area. On fresh surfaces the algal and foraminiferal lime- stone is usually white or light buff, but locally, where clay and other impurities are relatively abundant, it has a DIVISION OF MINES OLAF P. JENKINS, CHIEF ^° *^ ***' gK 1 UNITED STATES DEPARTMENT OF THE INTERIOR STATE OF CALIFORNIA GEOLOGICAL SURVEY DEPARTMENT OF NATURAL RESOURCES Monlerey tormolion Neor oose locolly includes thm beds equi- Lg volenl lo VoquerosH) ond Riocon VoquercsP) sondslont UNCONFORMITY EXPLANATION H icludes thin ■ VoquerosH) LZ1" iros(?) sonds 'CONFORM/ Sespe formolion UNCONFORMITY Cozy Dell shole Sierra Blonco limestone UNCONFORMITY □ "hin bedded shole ond ondstone. Neor lop massive if shole ond conglomerate. ofoss.c(?)inqge tonciscon group including n'rusive serpentine— Jsp Strike ond dip of beds Sirike ol vertical beds Conloci, occorolely locoled Contact, projected Conloci, inferred Fault, showing dip Fault, concealed UNIVERSITY OF CAUru SUmifo"* of types ond oges of r Anticline, showing trace of onol plane and bearing ond plunge ol a«is(Ooshed where approximately located) Syncline, showing trace ond dip ol oxial plone and bearing ond plunge ol oxis (Dashed where approximately located) Oeceaioer 1949 RECONNAISSANCE GEOLOGIC MAP OF PART OF THE UPPER SANTA YNEZ RIVER DRAINAGE BASIN SHOWING DISTRIBUTION OF THE SIERRA BLANCA LIMESTONE, SANTA BARBARA COUNTY, CALIF Sierra Blanca Limestone, Santa Barbara County 5 grayish cast. Limestone from some beds shows a mottled in the San Rafael Mountains. The markets of Los Angeles yellow staining caused by hydrated iron oxides. The iron have been amply supplied by Crestmore, Victorville, oxides may be derived from the abundant fragments of Riverside, and other easily accessible deposits. The excess limonite pseudomorphous after pyrite and glauconite ( ? ) carbonate materials produced have been sufficient to sup- found in the limestone. On weathered surfaces the Sierra ply Santa Barbara and other nearby towns. As long as Blanca limestone is gray to white. the limestone deposits near Los Angeles are actively pro- Mr. Leslie Larrieu, of Los Angeles, made quantita- ducing limestone products at low cost, the Sierra Blanca tive analyses of the Sierra Blanca limestone for M. F. limestone is not likely to be developed because of the Keenan, 4 and the data presented for samples 1, 2, 3, and 4 high cost of development and exploitation. A major item are taken from Keenan 's paper. These four samples of expense would be the extensive excavation of roads (probably grab) are from beds in the central part of the necessary to make the deposits accessible, limestone sequence at the type locality of the Sierra On Indian Creek in the northern area, where the Blanca limestone. Sample 5 (composite grab) was taken thickest and purest CaC0 3 rock occurs, the relief is suf- from the outcrops of Sierra Blanca limestone along Big ficiently great to expose on the canyon walls large Pine Mountain road, and sample 6 (continuous channel) amounts of limestone above creek level. Locally, favorable from the limestone near the junction of the Santa Ynez quarry sites may be found and the extensive limestone River and Blue Canyon. outcrops may sustain large-scale development for many These six samples from the Sierra Blanca limestone years, contain in excess of 90 percent CaC0 3 (table 1), whereas, Another possible site for a quarry is west of Indian according to F. W. Clark, 5 average limestone contains Creek, where the limestone crosses Big Pine Mountain only 76 percent CaC0 3 . The CaC0 3 content in individual road. Here, the beds locally have flattened, and the lime- samples ranges from 90.60 percent to 98.80 percent, and stone forms a large surface plate. The overburden is thin ; the average of the six samples analyzed is 95.07 percent jointing and fracturing are prominent; and though the CaC0 3 . Manufacturers that require rock with a very high limestone is not at its maximum thickness, it is sufficiently CaC0 3 content for industrial processes would find much thick to sustain a large quarrying operation, of the Sierra Blanca limestone suitable for their uses. Outcrops of Sierra Blanca limestone in Blue Canyon Impurities are present in negligible quantities and would and near the Santa Ynez River are sufficiently high in not lower the commercial value of the deposits. The prin- CaC0 3 to be commercially valuable for some uses. These cipal impurities in the limestone, MgO, Si0 2 , Fe 2 3 , and outcrops are more accessible than those to the north ; A1 2 3 , are largely contained in grains of quartz, glauco- however, in most places, the limestone is less than 50 feet nite, chert, hydrated iron oxides, magnesite, and green- thick and dips are steep. stone, and in clay particles. Although not enough limestone is available for a _ . _ , .. large operation, two or three smaller quarries could oper- Econom.cEvaluafon ate for several years without exhausting the supply of 1 hough possible quarry sites can be found in the j • ^ „ rac | e roc k northern area both on Indian Creek and to the east and ' Jointg are pregent in most areas and ghould f acilitate west along the strike of the limestone beds, exploitation quarrying . i n localities where joints are absent or poorly of the Sierra Blanca limestone has never been attempted. developed, costs of operation would be higher because The inaccessibility of the Sierra Blanca limestone and a f the ^ a nse of additional blasting and crushing. local market that has gained importance only in the past „ , , „ „ « m CT +™^ ^f ™+*vr. few vears have hindered development of the limestone To summarize, large tonnages of limestone of poten- tewyears nave nmdered development ot tne limestone ^ yalue &re available f or quarry i ng w hen exploitation is * Keenan, M. F., The Eocene Sierra Blanca limestone at the economicallv feasible. Features of the limestone that point type locality in Santa Barbara County, California: San Diego Soc. auiiumitaiy icoaiuic. c *- Nat. History Trans., vol. 7, No. 8, pp. 53-84, 1932. to profitable development are purity, thickness, and quan- 6 Clark, F. W., The data of geochemistry: U. S. Geol. Survey ,•. . Bull. 770, pp. 30, 33, 1924. tlty. Table 1. Partial analyses of the Sierra Blanca limestone. Samples 12 3 4 5 6 CaC0 3 90.60 97.00 98.80 98.00 94.76 91.29 CaO 50.73 54.32 55.33 54.88 53.07 51.12 MgO _ _ _ 3.00 0.71 0.32 0.66 1.14 1.36 AloO, ) °- 37 052 ■wfcZIZZIIZlI^^^ °- 94 056 °- 66 °- 33 °- 45 Si0 2 160 0.96 0.24 0.42 2.01 4.76 p.05 trace trace trace none (not analyzed) Samples 1, 2, 3, and 4. (From Keenan, M. F., op. cit.) According to Keenan these samples were from the type locality of the Sierra Blanca lime- stone on Indian Creek. Samples are from central part of limestone sequence and represent approximately 55 feet of stratigrapnic tnicKnes.;,. Samples 5 and 6. (Analyzed by P. T. Bee, Chief Chemist, Abbot A. Hanks, Inc., San Francisco, Calif.) Sample 5 from Big Pine Mountain ^road where limestone crosses road. Composite grab sample collected at 2- to 3-foot intervals in cuts along road crossing limestone mass, aampie represents a stratigraphic thickness of 70 to 80 feet. Sample 6 from north bank of Santa Ynez River, U miles west of Fendola '-uara Station. Continuous channel sample represents a 35- to 40-foot stratigraphic thickness, which in this area is the total tnicKness oi tne sierra. Blanca limestone. O 30664 7-50 2M printed in California state printing office Digitized by the Internet Archive in 2012 with funding from University of California, Davis Libraries http://archive.org/details/sierrablancalime01walk