■ ■ aw H California Division of Mines Sfieccai TRefi&it 70 COVER — One of the most distinctive features of the Kern River gravels is the abundance of white, light-brown, and pink quartzite pebbles. The quartzite, unusual in Sierran-derived gravel, contributes to the high quality of the aggregate. SAND AND GRAVEL RESOURCES OF THE KERN RIVER NEAR BAKERSFIELD, CALIFORNIA by HAROLD B. GOLDMAN Geologist, California Division of Mines and IRA E. KLEIN Geologist, U.S. Bureau of Reclamation UNIVERSITY OF CALIFORNIA DAVi^ JUN26 1962 LIBRA R / Special Report 70 1961 CALIFORNIA DIVISION OF MINES FERRY BUILDING, SAN FRANCISCO 11 ,, rfi- :■■■■ ■-■' , ■'.■■■ ■■■:■.- STATE OF CALIFORNIA EDMUND G. BROWN, Governor DEPARTMENT OF NATURAL RESOURCES DeWITT NELSON, Director DIVISION OF MINES :AMPBELL, Chief Special Report 70 Price $1.00 CONTENTS Abstract Introduction __ Geography _.__ _ __ General geology and history of the Kern River basin Aggregate-making properties of the source rocks in the Kern River basin Petrographic techniques used in evaluating the Kern River deposits Quality of materials as determined by routine laboratory tests Economic possibilities _.. Appendix Standard laboratory acceptance tests General specifications for concrete aggregate References Page 5 7 7 10 13 14 17 24 31 31 32 33 Illustrations Plate 1. Generalized geologic map of the Kern River drainage area Plate 2. Geologic map showing aggregate resources of the Kern River near Bakersfield Figure 1. Index map showing Kern River basin and map area of this report Figure 2. Diagram showing composition of the sand and gravel in the Recent stream bed of the Kern River Figure 3. Diagrams showing physical quality classification and roundness classification of samples from the Kern River floodplain, ter- races, and Kern River formation Stream bed of Kern River near Kern Canyon Floodplain of Kern River near Kern Canyon Quaternary terrace deposit and close-up Kern River formation and close-up Outcrop of metamorphic rock Outcrop of granitic rock Method of collecting a field sample for petrographic analysis Comparison of two gravels of differing form Photomicrograph of the heavy mineral fraction Pit in the Kern River formation showing lenticular nature of over- burden Dicco Inc. plant and pit Cal Rock Co. (Rinker Rock Co.) plant and pit Kern Rock Co. plant and pit Kern River Rock Inc. (River Rock Co.) plant and pit Griffith Construction Co. plant Griffith Construction Co. pit and close-up Coarse aggregate grading machine - Fine aggregate sieve shaker Los Angeles abrasion machine (L.A. Rattler) Sand equivalent test equipment _ Petrographic analyses of aggregates in the Bakersfield area Mineralogical analyses of a sand sample from the Kern River stream bed 6 miles southwest of Bakersfield Results of standard acceptance tests on processed aggregate from commercial deposits in the Bakersfield area __ Results of standard acceptance tests on unprocessed material from deposits of sand and gravel in the geologic formations near Bakersfield Table 5. Gradations of some unprocessed sand and gravel samples taken from commercially worked geologic formations near Bakersfield Table 6. Alkali aggregate reactivity test on Quaternary terrace deposit Table 7. Commercial sand and gravel producers in I960... Photo 1 Photo 2. Photo 3. Photo 4. Photo 5. Photo 6. Photo 7. Photo 8. Photo 9. Photo 10, Photo 11. Photo 12. Photo 13. Photo 14, Photo 15. Photo 16. Photo 17. Photo 18. Photo 19. Photo 20. Table 1. Table 2. Table 3. Table 4. In pocket In pocket 8 19 22 9 10 11 12 13 14 15 16 20 25 26 26 27 27 28 29 30 30 30 30 18 20 23 23 23 24 28 (3) Digitized by the Internet Archive in 2012 with funding from University of California, Davis Libraries http://archive.org/details/sandgravelresour70gold ABSTRACT Extensive deposits of sand and gravel are concentrated along the Kern River in Kern County between the city of Bakersfield and the mouth of Kern Canyon. Gravelly strata amenable to economic exploitation are present in the Recent floodplain deposits, in the Quaternary terrace deposits, and in the Pliocene Kern River formation which is an alluvial fan of the ancestral Kern River. The Recent floodplain deposits are of highest physical quality for use as concrete aggregate; the terrace deposits are slightly inferior; Kern River formation deposits are generally of a lesser but suitable quality because of the effects of post-depositional weathering. Gravel in the deposits of all three ages, Recent, Quaternary, and Pliocene, consist of similar rock types; but the three deposits differ from one another in the proportions of the various rock types represented — granitic rocks, metavolcanic rocks, quartzitic metasedimentary rocks, and micaceous schist and gneiss — reflecting the progressive unroofing of the Sierra Nevada batholith. The quartzitic metasedimentary rocks, which include a distinctive quartzite unusual in Sierran-derived gravels, add to the good quality of the ancient and recent Kern River deposits. The sands are composed predominantly of the disintegration products of the granodiorite of the Sierra Nevada batholith — feldspar, quartz, and lesser amounts of hornblende and mica. Although very minor amounts of reactive andesite volcanic rocks are present in the gravel and opaline coatings are locally noteworthy, the aggregates are, on the whole, chemically non-reactive. Field examination, petrographic studies, and laboratory tests indicate that high- quality concrete aggregate can be produced economically from Recent floodplain and Quaternary terrace deposits. Some are partially exploited and others are commercially undeveloped. The Kern River formation also makes acceptable aggregate, but large- scale development requires detailed exploration to avoid unsuitable areas. Commercial production of sand and gravel has centered in two areas, one in the floodplain of the Kern River and the Quaternary terraces northeast of Bakersfield; the other in the Kern River formation northwest of that city, in the western part of the West Front and Kern River oil fields. These deposits have been a source of concrete aggregate and roadbase materials for many years. Here is a remarkable case of large- scale aggregate production from a small area in which three different geologic forma- tions were mined. The formations (Recent floodplain, Quaternary terrace, Kern River formation), of different ages, represent three different stages in the geologic history of the Kern River. Operational problems vary with each formation depending upon the topography, status of industrial development, and the extent to which weathering has affected the older deposits. The total recorded value of sand and gravel producion in the Bakersfield area from 1915-60 approximates 12 million dollars. As a result of post- World War II expansion in construction activities, the value of annual production has steadily increased from a quarter of a million dollars in 1946 to over a million dollars in I960, when five sand and gravel operations were active. Pit operation coordinated with land' development offers possibilities for future ex- ploitation in the Kern River formation. (5) SAND AND GRAVEL RESOURCES OF THE KERN RIVER NEAR BAKERSFIELD, CALIFORNIA By HAROLD B. GOLDMAN and IRA E. KLEIN INTRODUCTION The California Division of Mines is conducting a min- eral inventory of the sand and gravel resources in the state in cooperation with federal and state agencies which have made detailed engineering geological investigations of construction materials for use in public work projects. One such investigation, which was made in 1949 by Ira E. Klein for the U.S. Bureau of Reclamation, was for sources of concrete aggregate along the lower reaches of the Kern River for use in the construction of the Friant-Kern Canal. Kern River drains a portion of the southern Sierra Nevada in Kern and Tulare Counties and, in the Bakersfield area, has deposited a great volume of gravelly alluvium which forms the basis of a thriving sand and gravel industry. Purpose. The purpose of this report is to present a general picture of the sand and gravel resources along the lower reaches of the Kern River near Bakersfield and their present state of development, and to call attention to those areas that might be of economic significance for future development. These sand and gravel deposits have been a source of concrete aggregate and road-base ma- terials for many years. Here is a remarkable case of large- scale commercial production of sand and gravel from a small area in which three geologic formations were mined. The formations, of different ages (Recent flood- plain, Quaternary terrace and Pliocene alluvial fan), represent three different stages in the geologic history of Kern River. Operational problems vary with each formation depending upon the topography, status of in- dustrial development, and the extent to which post- depositional weathering, generally of a mild character, has affected the older deposits. Because old terrace and Tertiary gravels are becoming increasingly important as sources of aggregate, an under- standing of the geological background in the Bakersfield area should stimulate the exploration and testing of an- cient gravelly alluvial deposits in other areas where stream bed and young terrace deposits are absent, de- pleted, or impractical to develop. Adverse weathering effects that require extra beneficiation and selective quar- rying can be more than offset by the advantages of bench-type pit operations. Scope. Samples from six commercial operations in the various types of deposits were subjected to systematic petrographic appraisal. Undeveloped terrace and flood- plain deposits were evaluated as potential sources of con- crete aggregate in a preliminary way. This evaluation included a field inspection in which such factors as depth of overburden, present land use, and weathering effects were considered. The materials may be evaluated by the reader for other less exacting purposes, such as bitumi- nous aggregate or base course, for which they may meet specifications. The results of standard laboratory tests made by state and federal agencies to determine the quality of materials in these deposits are presented herein and evaluated. A general description of the laboratory procedures used to evaluate sand and gravel deposits is included in the ap- pendix to assist the reader who is unfamiliar with ag- gregate testing. Although the mineralogic composition of the sands is of no immediate interest to the aggregate industry, de- tailed information on the mineralogy of fine sand from the stream bed of the Kern River has been included. The sands are characteristic of the Tertiary arkosic sediments, which are widespread in the eastern San Joaquin Valley. The expanded use of industrial minerals may make by- product extraction of feldspar or other minerals from Sierran-derived sands economically feasible. Many of the data used in this report were adapted from Mr. Klein's memoranda and records prepared for project-planning studies of the U.S. Bureau of Reclama- tion. This agency kindly has made the material available for publication. Mr. Goldman, geologist with the Divi- sion of Mines, compiled these data, collected additional information, examined the commercial operations, pre- pared the text and the geologic map of the drainage basin, and assisted in preparing the plates. The comments and the remarks are the personal non- official opinions of the writers and do not represent the official position of the government agencies with which they are associated. Geography The Kern River drains an area approximately 90 miles long by 30 miles wide on the west flank of the Sierra Nevada in Kern and Tulare Counties. The North Fork of the Kern River heads in the Mt. Whitney region and flows south for almost 80 miles to join the South Fork and form the main river at Isabella. Below Isabella, the (7) California Division of Mines Figure 1. Index map showing Kern River basin and map area of this report. Photo 1. Stream bed of the Kern River near the mouth of Kern Canyon, east of Bakersfield. Note the abundance of rounded cobbles and boulders. The gravel contains a large proportion of granitic rock types derived from the Sierra Nevada batholith which can be seen in the background. Kern River flows southwest through a deep and rugged canyon for about 31 miles, emerges on the floor of the San Joaquin Valley at a point about 12 miles east of Bakersfield, and then flows west to Buena Vista Lake. The area covered in this report is along the Kern River from the mouth of Kern Canyon to the vicinity of Bakersfield. 10 California Division of Mines General Geology and History of the Kern River Basin The Kern River drains the southern part of the Sierra Nevada geomorphic province. The upper part of the Kern River basin is underlain by the granitic rocks of the Sierra Nevada batholith and to a lesser extent by metamorphosed pre-batholith sedimentary and igneous rocks, as shown on the accompanying generalized geologic map of the Kern River drainage basin. The metamorphic rocks are pedants within the granite, repre- senting remnants of Paleozoic and Mesozoic marine sedi- mentary deposits such as limestone, shale, sandstone, limv mudstone, and interbedded volcanic flow-rock and tuff. These rocks were folded and dynamothermally meta- morphosed into marble, slate, quartzite, hornfels, amphib- olite, and quartz-mica schist, prior to and during the invasion of the granitic rocks in late Mesozoic time. The granitic rocks are principally biotite-hornblende granodi- orite that grade locally into granite, quartz monzonite, quartz diorite, and gabbro. After the emplacement of the batholith, the southern Sierra Nevada was subjected to a long period of erosion, repeated uplift and westward tilting, late Cenozoic vol- canic activity, and Pleistocene glaciation. During the Cenozoic era sediments derived from the Sierra Nevada were deposited in marine basins in the San Joaquin Val- Photo 2. Floodplain of the Kern River near Kern Can- yon. The low, flat surface in the center of the photograph is a Quaternary terrace. The bluffs on the left are underlain by the Kern River formation. View downstream to the west. 4 i. 4r ley. The thick sequence of shale, silt, sandstone, and con- glomerate that accumulated is now consolidated and unconformably overlies the granitic and metamorphic basement complex along the eastern margin of the San Joaquin Valley, and is of importance as a source of pe- troleum. Continuing uplift and erosion in late Pliocene time resulted in the deposition of a large alluvial fan (the Kern River formation) by the Kern River. Tilting of the Sierra Nevada rejuvenated the Kern River, which be- came entrenched in the fan. The fan was subsequently deformed into a broad structural arch that plunges gently to the southwest and is broken by many small faults. As the Kern River formation was arched upward, the Kern River continued to flow through and to deposit uncon- solidated sediments on the valley floor which was a half a mile to a mile wide. Renewed uplift of the Sierran block in Pleistocene time and the consequent entrench- ment and partial dissection of these deposits resulted in the formation of terraces along the lower reaches of the Kern River. Continued dissection of the ancient fan de- veloped the present topography. NATURE OF THE ALLUVIAL DEPOSITS Extensive deposits of sand and gravel are concentrated along the lower reaches of the Kern River from. Bakers- field to the mouth of Kern Canyon. Gravelly strata are present in Recent floodplain, Quaternary terrance, and the Pliocene Kern River formation,* which is an alluvial fan deposit of the ancestral Kern River. Recent Floodplain Deposits. Below Isabella Dam, the Kern River flows through a steep V-shaped canyon for about 31 miles, with an average gradient of 105 feet per mile, and debouches on the floor of the San Joaquin Val- ley about 12 miles east of Bakersfield. The regimen of the riven changes abruptly where it crosses the Kern Front fault at the mouth of Kern Canyon. Along this fault, crystalline bedrock formations on the east are in contact with Tertiary marine sedimentary rocks on the west. After leaving the canyon, the river flows with a gradient of 58 feet per mile. Along this reach, in flood stage, the river transports cobble- and boulder-size gravel which is deposited for a distance of about 3 miles below the mouth of the canyon. The terrace and present river deposits are highly bouldery in this interval. Below the tributary Cottonwood Creek (the only major tributary to join the river after it leaves the mountains), the Kern River flows with an average gradient of 9 feet per mile and transports relatively small amounts of gravel. In the 5-mile interval between Cottonwood Creek and Kern River Park the Recent floodplain of the Kern River con- tains sand and pebble-to-cobble gravel. These floodplain deposits range from half to three-quarters of a mile in width and are as much as 30 feet thick. Below Kern River Park, only sand is transported by the river. * The Kern River formation is widely regarded as Pleistocene to Pliocene in age. Recent work by Mr. Klein on cores taken from shallow drill holes in the San Joaquin Valley indicates that a more probable age designa- tion is Pliocene. Stratigraphic criteria establish the position of the Kern River formation below the Corcoran clay, which is considered to be Plio- Pleistocene on the basis of diatoms (Frink & Kues, 1954). Sand and Gravel Resources, Kern River 11 Photo 3. Quaternary terrace deposit of sand and gravel adjacent to the Kern River northeast of Bakersfield. The thick sandy layer overlying the gravelly layer is overburden that must be stripped off. The gravels, which are finer than those in the Kern River formation, contain pebbles, cobbles, and some boulders. The adjacent floodplain deposits of the Kern River are composed of coarse sand and little or no gravel. Inset: Close-up of the gravels in the terrace deposit. Note the high degree of rounding, a feature unusual in an alluvial deposit in California. Many of the cobbles are massive quartzite. Quaternary Terrace Deposits. River terrace deposits averaging half a mile in width border the Kern River for approximately 12 miles to the northeast of Bakersfield. These benchlike deposits above the level of the present floodplain are irregular in plan. In the vicinity of Bakers- field the terrace deposits are about ]/ 2 to 1 square mile in areal extent and average about 40 feet thick. The deposits contain irregularly stratified, uncemented layers of buff- colored sandy and gravelly material. The sand layers, which range from 2 to 20 feet in thickness, inter finger with weakly indurated conglomeratic layers of similar thicknesses. The gravels, which are finer than those in the Kern River formation, contain well-rounded pebbles, cobbles, and some boulders. Ordinarily the upper 5 to 10 feet contain sandy overburden that must be stripped off for commercial exploitation. Quaternary terrace deposits, now partially depleted as a result of commercial opera- tions, are also located along the tributary Cottonwood Creek. 12 California Division of Mines * it , & Jr'yW' %*} fikJ4 -i j. .. Photo 4. Kern River formation exposed in road cut on China Grade road near Bakersfield. Note irregular stratification of sandy and gravelly material in the conglomeratic portion of this relatively uncemented, weakly indurated formation. The gravels are coarser in this formation, which contains abundant boulders, than the gravels in the Quaternary terrace deposits. The Kern River formation is a commercial source of sand and gravel. Kern River Formation* The Kern River formation, first named by Anderson (1905, p. 187-190), is a series of nonmarine sediments of Pliocene age resting discon- formably on upper and middle Miocene sedimentary rocks in the low mesa area north and east of Bakersfield. The thickness of the formation ranges from 200 to 1000 feet. The top of the Kern River formation is a surface of deposition sloping gently into the San Joaquin Valley and is now elevated and dissected. The Kern River for- mation is composed of indistinctly bedded, light gray- buff gravels, sands, and light reddish-buff to greenish silts and clays. Boulders averaging one foot to several feet in diameter are present at the base. The formation tends to become finer downdip to the west. * Information from unpublished manuscript by T. W. Dibblee, Jr. Photo 4 inset: Close-up of the conglomeratic por- tion of the Kern River formation. The sand and gravel show slight to moderate weathering effects. The fracture in the pebble in the center of the photo- graph is a result of post-depositional weathering. Sand and Gravel Resources, Kern River 13 In the Bakersfield area, the Kern River formation crops out over a vertical interval of about 100 feet on both sides of the Kern River. Crudely stratified, weakly cemented, well-rounded cobbly and bouldery lenticular beds 10 to 15 feet thick, dipping gently to the west, are in the formation in this area. Sand lenses 1 to 12 feet thick are interbedded with the conglomeratic layers. The formation coarsens to the east and becomes excessively bouldery— from the standpoint of aggregate production— 5 miles east of Bakersfield. To the north of Bakersfield the formation becomes less gravelly, and in the Poso Creek area about 5 miles to the north consists predom- inantly of sand and silt. Post-depositional weathering of a mild character has affected some portions of the for- mation. Soft, deeply weathered gravel and caliche layers are occasionally encountered. Opaline or calcareous coat- ings are present on some of the gravel in local areas. The ancient Kern River, which deposited the Kern River formation, was a more competent stream than the present Kern River or the river which formed the terrace deposits. This is borne out by the comparison of the rel- ative coarseness of these deposits at any given distance from the mountain front. The ability of the Kern River to transport coarse detritus appears to have diminished, probably progressively, since the Kern River formation was deposited. Thus, at a point about a mile upstream from Bakersfield, the present stream bed is sandy and devoid of fine gravel, the terrace deposits contain coarse pebble gravels, and the Kern River formation contains cobble gravels. AGGREGATE-MAKING PROPERTIES OF THE SOURCE ROCKS IN THE KERN RIVER BASIN The nature of the sediments in a stream is determined in a large part by the source rocks within the drainage area. The aggregate-making properties of the lithologic units drained by Kern River are discussed below. Although the geology of the Kern River basin has not been completely mapped, it is fairly well known and is presented in a generalized form on plate 1. Metamorphic Rocks (Map Symbol m). Metamorphic rocks crop out randomly throughout the basin as pen- dants within the granitic mass. The largest pendant that has been mapped is in the vicinity of Isabella Lake and trends north along Kern Canyon. Smaller pendants are in the foothills along Cottonwood Creek. The non-schistose metavolcanic rocks, hornfels, and quartzitic metasedimentary rocks contribute hard, dense, tough pebbles, which are characteristically well rounded and very sound, and which add to the good quality of the Kern River gravel. The micaceous schist and gneiss contribute some less sound pebbles, which tend to have flat shapes. The quartzitic metasedimentary rocks, which make hard, dense, tough, well rounded, very sound pebbles, include much true quartzite— a rock type which, although common elsewhere, is rather localized in its occurrence in much of California. One of the most distinctive fea- tures of the Kern River gravels is the abundance of white, light-brown, and pink quartzite pebbles and cob- bles. In that respect, these gravels are readily distinguish- able from other Sierran-derived gravels. Aggregate derived from the metamorphic rocks is satis- factory for use in concrete. Granitic Rock (Map Symbol gr). Plutonic igneous rocks of the Mesozoic Sierra Nevada batholith are ex- posed over the bulk of the drainage basin. The dominant rock type is biotite-hornblende granodiorite. More sili- ceous types such as alaskite, aplitic and porphyritic gran- ite, and the more basic diorite and gabbro, are also pres- ent. The diorite and gabbro are chiefly border facies. During weathering and fluvial transport, the grano- diorite distintegrates more readily into finer particles than the siliceous and basic rocks. These particles comprise the characteristic hornblendic arkosic sand that typifies the Sierran fluvial deposits. The finer-grained siliceous granitic rocks are more durable than the more micaceous, coarser-grained granodiorite and although less wide- spread, are selectively concentrated. Thus, in the pebble fraction the siliceous granitic types are more abundant than the granodiorite; the sand is derived almost wholly from the granodiorite in the drainage basin. The granitic rock types contribute dominantly hard, well-rounded, sound pebbles, though a small percentage of the pebbles is angular, deeply weathered, and un- sound. The gabbroic rock types form dense, tough peb- bles that are rarely unsound. Aggregate derived from the granitic rock unit is good and satisfactory for use as concrete aggregate. Photo 5. Outcrop of metamorphic rocks in the Sierra Nevada. Similar rocks occur as pendants in the granitic batholith in the upper Kern River basin. Photo by Charles W. Chesierman. 14 California Division of Mines Photo 6. Outcrop of granitic rock in the Sierra Nevada. Similar rock types in the Kern River basin contribute materially to the sand fraction of the deposits farther downstream. Phofo by Charles W. Chesterman. iSftifc^f^-'S/ia w " Undifferentiated Tertiary Sedimentary Rocks (Map Symbol Tj. A thick belt of Miocene marine and Mio- cene and Oligocene nonmarine shale, siltstone, sandstone, and conglomerate crops out along the Sierran foothills. This unit is not significant as a source of aggregate be- cause practically no gravelly detritus is contributed to the deposits except by reworking of the conglomerates. Tertiary Volcanic Rocks (Map Symbol TvL Tertiary volcanic rocks, chiefly andesite, crop out high in the basin south of Kern Lake, and in isolated patches in the Kernville quadrangle. Andesite porphyry pebbles that probably originated in these volcanic areas have been noted in gravel of the Bakersfield area as a minor constituent of the Kern River formation, in terrace deposits of Cottonwood Creek, and in insignificant amounts in the other deposits. These andesite pebbles are unmetamorphosed glass-bearing por- phyries similar to known alkali-reactive types and thus may be potentially chemically reactive. The pebbles derived from this unit are fairly sound, but some deeply weathered unsound fragments may be present. Quaternary Volcanic Rocks (Map Symbol Qvj. Quaternary basaltic volcanic flows and cinder cones are present high in the basin. These small distant areas of basalt are not significant as a source of detritus for the Bakersfield gravel deposits. PETROGRAPHIC TECHNIQUES USED IN EVALUATING THE KERN RIVER DEPOSITS An evaluation of the quality of material in the Kern River deposits was accomplished by petrographic anal- ysis, which, as used here, was based on the detailed scrutiny of samples by geologists specially trained in con- crete technology and in laboratory analysis and classifi- cation of rocks. Analyses of material of otherwise unknown usability for aggregate were compared with analyses of aggregates of known quality produced at commercial operations near Bakersfield and elsewhere in northern and central California. Commercially produced aggregates which have good concrete service records were used as yardsticks to measure the suitability of the unproved deposits. Standardization of methods for mak- ing such studies is a relatively recent development. The scheme followed in the study of the Kern River ma- terials was developed by Mr. Klein during the period 1947-48 while he was appraising gravel deposits in central and northern California in connection with water- development projects of the federal government. This scheme was also used in the study of Cache Creek ag- gregates (Klein and Goldman, 1958). The laboratory procedures and various quality categories followed in this scheme, described below, arc a modification and— in certain respects— an expansion of the U. S. Bureau of Reclamation procedures as described by Mielenz (1946, 1954), and Rhoades and Mielenz (1946). In 1954, the American Society for Testing Materials adopted a stand- ard method for petrographic examination of aggregates for concrete, ASTM Designation C 295-54, that is highly recommended for general usage. As a result of Klein's work it is felt that a competent petrographer can estab- lish readily the relative merit of an alluvial material as concrete aggregate, and can predict reasonably well, ex- cept for very marginal conditions, whether or not the material will pass or fail the various standard acceptance tests. However, petrographic examination is not recom- mended as a substitute for, but rather as a very valuable supplement to, laboratory tests. Closely coordinated geo- logic field work and petrographic evalution can cut down on expensive and time-consuming sampling and laboratory programs. Laboratory Procedures. The examination of the gravels of selected samples began with a detailed study of the 1 y 2 - to % -inch fraction. Selection of this grade was a matter of practical convenience, as the particle lends itself well to laboratory work. Each pebble in a minimum-size sample of 200 particles was classified ac- cording to (1) lithology, (2) physical soundness or strength characteristic, (3) chemical quality, and (4) form, in which two factors, roundness and flatness, are considered independently. In practice, in connection with the preliminary or reconnaissance type of aggregate in- vestigation, this 200-pebble minimum-size sample amounts to all the l'/ 2 - to %-inch pebbles in a pit-run sample of about 100 pounds. Experience has shown that for the ordinary stream-bed gravel deposit, examination of the Sand and Gravel Resources, Kern River 15 Photo 7. Method of collecting a field sample of a deposit for petrographic analysis. A portable sieve shaker is used to obtain the % to 1 Vi inch pebbles, a size most useful for petrographic study and one of commercial significance. minimum-size sample indicated above is sufficient to es- tablish the essential petrographic character of the deposit and permit broad classifications of physical and chemical soundness, and form features. In the case of terrace gravels, or unconsolidated ancient fluviatile sediments where the effects of weathering and cementation may be variable in different parts of the deposit, partial anal- yses of other sizes are also conducted. The lithologic and mineralogic composition, soundness, and form character- istics of the sand fraction were also systematically scru- tinized after the sample was separated into the sieve sizes conventional for grading concrete aggregate. Lithologic Classification. In making a lithologic classi- fication, pebbles and sand grains were divided into indi- vidual groups based upon lithology and mineralogy. This permitted the complete correlation of the lithologic com- position with physical and chemical properties such as soundness, reactivity, shape, and rounding. Attention was focused upon those rocks and minerals that might have a detrimental effect on the concrete-making qualities of the aggregate in which they are included. Physical Quality (Soundness) Classification. To make the physical quality classification, each constituent parti- cle of a sample representing, a particular grade size (with emphasis on the l'/ 2 - to %-inch pebble) was allocated to one of three "soundness" categories. A pebble or sand grain was classed as "good" and "satisfactory" in sound- ness if it was considered to be stronger than the cement matrix to enclose it; "fair" in soundness if it was con- sidered to have about the same strength as normal con- crete; and "poor" in soundness if it could not utilize the ; • ■La/-' full strength of the cement paste. Each pebble was ex- amined individually for structural, textural, and com- positional features affecting its strength characteristics. Although impact is not a type of stress to which pebbles embedded in concrete are normally subjected, observa- tion of the manner in which the pebble failed under hammer blows (crumbling, splintering, cracking on joints or bedding, etc.) was useful in evaluating the soundness. The classification of the individual pebbles as "good" and "satisfactory", "fair", and "poor" expressed the petro- grapher's opinion of the extent to which they would con- tribute to or detract from the quality of the concrete. The proportions of these types permits an appraisal of the aggregate as a whole, in which a triangular diagram is used to complete the classification. The triangle is divided into five principal fields representing differing degrees of physical soundness and corresponding suita- bility for use in concrete. The fields are: A, excellent for use in concrete; B, highly suitable; C, suitable for the low-medium strength and abrasion-resistant require- ments of concrete in moderate climates; D, same suita- bility as C but usable only if better material is not eco- nomically available; and E, unsuitable. Chemical Quality Classification. Individual particles were examined for potentially chemically reactive in- gredients—either in the particles or as exterior coatings— and potentially reactive andesite was noted in some de- posits. An actual count was made of the number of andesitic rock types present in each grade size and the relative percentages were tabulated. The presence of opaline or calcareous coatings was determined and noted on the petrographic table (Table 1.) 16 California Division of Mines Form Classification (Roundness and Flatness). The form of the pebbles and sand grains comprising an ag- gregate has a direct bearing on its concrete-making prop- erties. Concrete made with rounded particles requires less cement and work than concrete made with angular frag- ments. Flatness is independent of the degree of rounding (which is based on the sharpness of the corners and edges), and is of importance in concrete; for flat par- ticles have the same detrimental effect on workability, water, and cement content as angular particles. There is also a tendency for flat particles to become oriented horizontally in concrete; this has a harmful effect on bonding, because water accumulates beneath the particles. Angularity can contribute to the comparative inferiority of an aggregate, but in itself angularity would not lead to the rejection of an aggregate source. The widespread use of quarried crushed rock, where suitable stream deposits are not available, attests to this. In contrast, the degree of flatness of gravel is more critical because satis- factory concrete cannot be made when an aggregate contains an excessive number of flat particles. The degree of roundness and flatness generally changes with the dif- ferent grade sizes in a particular aggregate, but there is a different relationship between size and flatness than be- tween size and roundness (Krumbein and Pettijohn, 1938, p. 277-302). Size and flatness are dependent upon the original shape of the particle. The shape of a particle is determined essentially by its internal structure (lithology and mineralogy, texture, jointing, bedding, foliation, and cleavage) and is generally only slightly modified during transportation. Therefore, the degree of flatness of the sizes is governed by the proportions in which schistose, foliated, thin-bedded, slaty, platy jointed rocks or mica- ceous minerals are present in the various grades. During stream transport the external form of sedimen- tary particles is progressively modified, and there are stages in the degree of rounding which provide a natural basis for a threefold classification of the individual pebble. When a rock or mineral fragment begins its sedimentary history, its exterior form may be described as composed essentially of fracture surfaces (including bedding joints and mineral cleavage planes). With respect to the sharp- ness of corners and edges, or lack of rounding, the par- ticle is no different than a crushed rock fragment. This state of angularity is not restricted to the very early stage in the sedimentary history of the particle. In fact this feature may be outstanding in sands transported tens or even hundreds of miles. One of the processes resulting in diminution of stream-transported pebbles and sand grains is disintegration by cracking and crumbling; thus completely unrounded particles may be continuously formed. This fracturing process and subsequent rounding by abrasion depend upon the internal structure and size of the particles and on the conditions of stream flow. Angular particles, that is, particles not perceptibly rounded, may abound in certain size fractions and appear to be— to some extent— in all alluvial sediments. For ex- ample, granitic detritus, such as that found in the^Kern River deposits, is gradually rounded by stream transport to pebble and cobble sizes. However, as the particle di- minishes to pea-gravel size, it loses strength; and as it is bounced along the stream bottom it crumbles into angular arkosic sand. In this investigation, particles whose edges and corners were slightly rounded, but which were bounded mainly by original fracture surfaces, were classified as "angular". Another natural point in the rounding process is reached when all traces of the fracture surface are removed. Photo 8b (below). Aggregate containing harshly "angular" and some "subangular" particles. Photo 8a (above). Particles classified as "sub-angular to subrounded." Sand and Gravel Resources, Kern River 17 Particles at or beyond this state in degree of rounding were classified as "well-rounded". Particles which had not reached this state were termed "intermediate" ("sub- rounded to subangular"). The percentage of particles in each stage was plotted on a triangular diagram, in which the triangle was used to graphically allocate each sample into one of seven broad groups: very well-rounded, well-rounded, rounded, sub-rounded, sub-angular, angular, and very angular. The procedure followed for classification of particle shape or degree of flatness was very simple. The flat particles were visually separated from those that were not flat. Elongated, spindly, or rod-like pebbles, or slender prismatic sand grains, have the same harmful effects as excessively flat particles, therefore they were grouped with the flat particles in this classification. On the basis of the percentage of flat particles present, an aggregate was placed into one of four groups: 0-7 percent, equant; 7-15 percent, normal; 15-25 percent, tabular; and plus 25 percent, excessively tabular. QUALITY OF MATERIALS AS DETERMINED BY FIELD AND PETROGRAPHIC EXAMINATION Reconnaissance field and petrographic examination in- dicate that high-quality concrete aggregate can be pro- duced economically from both partially exploited and commercially undeveloped Recent floodplain and Quater- nary terrace deposits along the Kern River. The largest and most favorable deposits are mainly in section 2, T. 29 S., R. 28 E., section 35, T. 28 S., R. 28 E., and sections 4 and 5, T. 29 S.,.R. 29 E. The section 2 deposit (petro- graphic sample 3 on table 1) on the north side of the Kern River is the most favorably located. The Kern River formation gravels make acceptable concrete aggregate with proper processing, although it is necessary to avoid or waste intensely weathered areas. Sample 4 is composed of unprocessed moderately weathered acceptable gravel, and sample 5 is composed of deeply-weathered sub-standard gravel. These represent the range of materials which would be encountered in quarrying the Kern River formation. Observations on lithology, physical soundness, chem- ical quality, and form are presented in table 1, Petro- graphic analyses of aggregates in the Bakersfield area, and are summarized below. The samples of unprocessed pit- run materials were taken from commercially operated pits in Recent floodplain and Quaternary terrace deposits of the Kern River; the Kern River formation; and" the Quaternary terrace of Cottonwood Creek, a tributary to the Kern River. Lithologic Classification. The composition of the huge gravel formations was not conclusively determined, as only six samples of the l'/ 2 - to %-inch gravel were evaluated petrographically for their concrete-aggregate quality. Nevertheless, it appears that there are more meta- morphic and fewer granitic particles in the older Kern River formation than in the Quaternary terrace and Recent floodplain deposits. Although the Kern River for- mation contained a small number of fragments of Terti- ary andesitic volcanic rocks, none was detected in the younger deposits. The sands, reflecting the overwhelming abundance of granodiorite in the drainage basin, were not found to be significantly different from one another. The difference in the composition of the gravels re- flects the geologic history. When the Kern River forma- tion was being deposited, the metamorphic and Tertiary volcanic rocks underlay a greater area than at present, consequently the proportion of pebbles derived from these formations was larger. These proportions became progressively smaller as erosion of the basin continued; the metamorphic areas were reduced to scattered pend- ants, and the once extensive lava fields to minor patches. This resulted in the detritus containing more granitic types in the younger deposits. The primary compositional differences between the gravels are not believed to be significant as far as the comparative aggregate quality is concerned. In the Kern River formation, post-depositional weathering, which is more severe but highly variable in intensity, accounts for the relative inferiority of these materials. The principal rock types in the 1 y 2 - to % -inch frac- tion of the Kern River formation samples were found to be sub-schistose to massive metavolcanic and quartzitic metasedimentary rocks. Granitic rocks, chiefly siliceous aplitic and porphyritic types, along with a considerable amount of the characteristic Sierran biotite-hornblende granodiorite, make up about a quarter of the pebbles. Micaceous schist, gneiss, and andesite porphyry are minor constituents. In the Quaternary terrace and recent deposits, granitic rocks are appreciably more abundant, making up nearly half of the pebbles. The gravel in the Quaternary terrace of Cottonwood Creek is derived from reworking of the Kern River formation; therefore the rock types are present in pro- portions more closely akin to those of the Kern River formation than those of the Quaternary terrace. Quartzite, a distinctive and conspicuous rock type, contributes much to the high quality of the gravels. The quartzite makes up about one-third of the pebbles classi- fied as quartzitic metasedimentary rocks, most of which are impure or gnessic types. The quartzite pebbles and cobbles are hard, round, dense, and resistant components. The sand fraction (minus #4 sieve size— following aggregate terminology) of all the deposits, typical of detritus transported by Sierran rivers, is composed pre- dominantly of the disintegration products of the wide- spread biotite-hornblende granodiorite which underlies most of the Sierra Nevada. These harsly angular arkosic sands are composed of quartz, potash and soda lime feld- spar, and substantial but lesser amounts of hornblende and mica (biotite). Although mica is a conspicuous consti- tuent, normal washing to remove silt is thoroughly ef- fective in removing part of the mica if it is present in excessive amounts. 18 California Division of Mines Table 1. Petrographic analyses of aggregates in the Bakersfield area. Map Reference No. LITHOLOGICAL CLASSIFICATION of IK to %" gravel based on counts of 200 to 300 pebbles for each sample Type of gravel deposit represented by sample Note: Number in parenthesis is % of total "unsound" (where in excess of 1%). See Physical Quality classification below for complete summary of soundness. PERCENTAGES Kern River Recent floodplain Quaternary terraces Kern River Formation Pliocene alluvial deposits of ancestral Kern River Cottonwood Creek Quaternary terrace PLUTONIC IGNEOUS ROCKS GRANITIC Dominantly hard, sound, well-rounded, quartz-bearing, medium- grained rock. A few percent (as indicated at right) are angular, deeply weathered, unsound. Alaskite and aplite abundant; hornblende-biotite granodiorite very common; gneiss, porphyry, and pegmatite rare. GABBROIC Dense, tough, medium- to fine-grained, dark rocks. Rarely unsound. Gabbro; with minor diorite and diabase. META VOLCANIC ROCKS— MASSIVE TO SUBSCHISTOSE ACIDIC TO INTERMEDIATE Hard, massive, very fine-grained, light-colored rock. Fresh in recent gravels, but commonly weathered and unsound in older (terrace and Kern River fm.) deposits. Weakly to moderately recrystallized meta- rhyolite and metadacite; minor meta-andesite. INTERMEDIATE TO BASIC (AMPHIBOLITIC) Hard, dense, very fine-grained rock; weakly schistose to gneissose. In part weathered and unsound in the older deposits. METASEDIMENTARY ROCKS— MASSIVE TO SUBSCHISTOSE QUARTZITIC Hard, tough, very sound, massive to subschistose or gneissic. METASEDIMENTARY ROCKS— SCHISTOSE MICACEOUS SCHIST AND GNEISS Flat fragments; fairly sound in recent gravels, but soft, fractured and fissile in older deposits. VOLCANIC ROCKS— UNMETAMORPHOSED ANDESITIC Fairly sound to deeply weathered, rounded red-brown fragments. Glass-bearing porphyries; chemically deleterious. 39 (3) 14 10 27 3 44 (4) 25 (8) 11 (4) 17 2 (2) 43 (5) 21 (5) 22 11 19 2 35 (6) 9 (2) 27 2 (2) 27 (6) 16 23 (9) 11 (5) 33 (4) 3 (3) 36 (2) 6 (2) 36 4 (3) PHYSICAL QUALITY CLASSIFICATION (Based on petrographic criteria) "Good" and "Satisfactory" "Fair" " Poor" . .----- Suitability for use as concrete aggregate based on percentage composition of good, etc., as indicated by plotting on triangular diagram. For meaning of letter symbol see figure 3. 71 23 6 B 55 26 19 C 70 23 7 B 49 35 16 C 35 38 27 E 57 34 9 C CHEMICAL QUALITY The service records of Kern River aggregates indicate their non-reactive character. Andesitic rocks similar to known alkali-reactive types are the only dele- terious constituent found. They are limited to the Kern River formation and the Cottonwood Creek deposit where they comprise an insignificantly small fraction. Pebbles in the Kern River formation and the terrace alluvium are vari- ably encrusted, chiefly with non-reactive carbonate ("caliche") but occa- sionally with opaline matter. ANDESITIC ROCK CONTENT Wi'toH" M"to V s " #4- Sand Coatings ("caliche" and " opaline") Classification of deposit N — Non-reactive N* — Non-reactive, except when encrusted excessively None N Present N* Trace N* 2 IK 1 Present N* 2 1 1 Present N* 1 Trace N* ROUNDNESS CLASSIFICATION Degree of rounding Well-rounded Sub-rounded and sub-angular Angular Classification based upon percentage composition of well-rounded, etc., as indicated by plotting on triangular diagram in figure 3. Note: Most of the angular pebbles in samples 4 and 5 in particular, result from post-depositional weathering. The degree of rounding when deposited was probably similar to that in the less weathered deposits. 23 67 10 22 61 17 Well-rounded 30 60 10 Very well- rounded 10 69 21 14 63 23 Sub-rounded 11 66 23 Sub-rounded FLATNESS CLASSIFICATION Percent of sample VERY FLAT Classification 7 Equant 5 Equant 5 Equant 7 Equant 5 Equant 7 Equant Sand and Gravel Resources, Kern River 19 Z E GRADES 100 30 - 20 - * io -: SAND N5 30 GRANITIC NS 50 N2 100 mfflm&mM&mv.®&£ L A G I C L A S E 5,' 'Jfiltg&it*? 'irV.t.F ELDSPARu, *C==**=„v. '***fet iM%£ ALKALI FELDSPAR jj jj j j jjjjb jjjjjjj •; JJJJJ JJJ J j|; jjjjjjjjj. jITJ'TT tt 1 Hffll iijij- OPAQUES #1 .v\^avp^ jjjjjjjjjj jjjjjjjj jjjjjjjjjj jjjjjjjjj jjjjjjjjjj jjjjjjjjjj JJJJJJJJJ JJJJJJJJJJ JJJJJJJJJJ JJJJJJJJ J JJJ JJ J J JJJJJJJJ JJJ JJJJJJJ JJJJJJJJJJ J J JJJ JJJ JJJJJJJ JJJJJJJJJJ *,,=>«. 11*0* »*,,*. lli#i« « «' ►»s»_.s - L** ii *«,;«>„, //, _: = *.«* ^^■IMI,?,.^.. 00 MICA OTHER HEAVY MINERALS Figure 2. Composition of sand and gravel in Recent stream bed of the Kern River. Dashed lines indicate estimated proportions based upon interpo- lation from adjacent analyzed material. In the #4-#8 and #8-#16 grades, granitic rock particles are more abundant than free quartz and feldspar grains; and 5 to 10 percent of the grains are metamorphic rocks, chiefly schist, phyllite, and quartzite. The #16-#30 grades and finer sands are composed predominantly of mono- crystalline grains of quartz and feldspar. The mica content (of unprocessed sand) ranges from 2 to 4 per- cent. The #4-#8 and #8-#16 sands are "angular", the #16- #30 and finer are "very angular". The lithologic and mineralogic composition of the sand is presented in figure 2. 20 California Division of Mines The growing demand for industrial minerals suggests Table 2. Mineralogical analyses of a sand sample from the Kern a future use for the sand as a source of alkali-feldspar, River stream bed 6 miles southwest of Bakersfield. quartz, and certain of the heavy minerals. They could Sample is a well-sorted, fine-medium sand. be removed as a by-product in aggregate production, A. Total constituents in sand or as separate operations in conveniently located deposits SIZ E ANALYZED Fine (%-% mm.) Very fine (^-l/i6mm.) e i • j » c -i • u- u ^i. Major constituents Percent Percent of arkosic sand. As seen in figure 2, in which the com- Quartz 37 8 Not position of the various size-grades are diagrammatically Plagioclase feldspar 39.5 presented, the finer sand sizes are most advantageous for A .' k ^ 1 feldspar 14.0 analyzed separation of feldspar and other minerals. Huge quantities Hornblende (see B)"- S-7 20 3 of fine sands in which these sizes predominate are de- Opaque minerals (see B)__ 0.4 4.1 posited in the broad washes, floodplains, and alluvial fans 0t ( h s ^ Jf av y minerals of the Kern River and other Sierran streams in the eastern ~ "~~ '_ _ portion of the Upper San Joaquin Valley. Total 100.0 No detailed mineralogical study was made of the heavy B. Total heavy minerals in sand minerals in the samples taken from the aggregate pits. Hornblende 79.6 68.5 However, data are available on a sample taken from the °minerals {TfiSSfoT 17 39 sandy bed of one of the distributaries on the Kern River Other heavy minerals fan about 6 miles southwest of Bakersfield. This sample ( se e C) — 15.4 18.0 was analyzed by the authors in 1953 in connection with Total 1000 inon groundwater geologic studies of the U.S. Bureau of Re- „ „ . , , , , T, 1 ^ 1 • 1 c u c ^- ^erru-quanntative analyses of heavy minerals clamation. The complete mineralogic analysis of the fine (exclusive of hornblende and opaque minerals) ( l A-Va mm) and the very fine ( Va-1/16) fraction is pre- Percent sented in table 2. Epidote Very abundant 25-50 The composition of this sample is typical of the Kern p River fine sands. Local variation would be expected in Clinopyroxene Abundant 10-25 the biotite and heavy mineral (specific gravity > 2.96) patite, garnet content, reflecting changes in local conditions of sedi- Monazite, zircon Common 3-10 mentation. Although an interesting variety of minerals Andalusite Sparse 1- 3 is present in the heavy mineral suite, reflecting the Sierran Hypemhene granodiorite and associated metamorphic derivation, noth- Tourmaline Rare ^0^ & Photo 9. Photomicrograph of the heavy mineral fraction > 2.96, in the Kern River sand under ordinary light. H— hornblende, Z— zircon, S— sphene, G— garnet, E— epidote. Sand and Gravel Resources, Kern River Physical Quality (Soundness) Classification. The Re- cent floodplain deposits are of high quality for use as concrete aggregate. The Quaternary terraces are of suit- able to high quality. The Kern River formation generally is of suitable quality but is unsuitable, without beneficia- tion, in areas that contain excessive amounts of unsound, weathered particles. In the Recent floodplain and Quater- nary terrace gravels, 60 to 70 percent of the pebbles ex- amined were of "good" or "satisfactory" soundness, about 25 percent were "fair", and the remainder "poor". From 35 to 49 percent of the pebbles examined in the Kern River formation samples were of "good" or "satisfactory" soundness, 28 to 35 percent were "fair", and the re- mainder "poor". The exact proportions of "good and satisfactory", "fair", and "poor" pebbles in the samples from the individual deposits are presented in table 1. Chemical Quality Classification. All the Kern River aggregates are nonreactive. There have been no reported instances of concrete failures attributed to alkali-aggre- gate reactivity. Mortar-bar tests made by the Materials and Research Department of the Division of Highways substantiate the nonreactive character deduced from the petrographic study and service records of concrete made from Kern River aggregate. Petrographic examination revealed only two constituents that could be considered potentially chemically reactive: (1) hemicrystalline an- desitic and dacitic pebbles present in minor amounts up to 2 percent in the % - to l l / 2 -inch gravel of the Kern River formation, and less than 1 percent in the younger deposits, and (2) opaline coatings associated with calcium carbonate encrustations present on some pebbles in the Kern River formation, and to a lesser extent in the Quaternary terrace deposits. The possibly reactive volcanic materials do not war- rant special consideration, as they are present in minor amounts. The distribution of the opaline coatings, which on the whole appear to be localized and minor, should be watched while exploiting the older gravel deposits. Form Classification (Roundness and Flatness). The pebbles in the Recent floodplain and Quaternary terrace deposits of the Kern River exhibit a remarkably high degree of rounding for a California alluvial deposit. The rounding reflects the distant origin of the durable crys- talline rocks from which the pebbles were derived and the vigorous abrasive action of transport by the Kern River. In the 1 '/ 2 - to % -inch size, well-rounded pebbles comprise from 22 to 30 percent, sub-rounded to sub- angular pebbles from 51 to 62 percent, of the total sample. In the scheme followed these gravels are classi- fied as "well-rounded to very well-rounded". Angularity increases rapidly with decrease in particle size, especially when the granitic detritus is less than %-inch, and the sand is harshly angular. The gravel produced from the Kern River formation is somewhat more angular than gravels from the other formations partly because of breakage in handling that results from the weakened con- dition induced by post-depositional weathering. Well- rounded pebbles comprise only 10 to 14 percent, and 21 angular pebbles from 21 to 23 percent, of the total sample. These aggregates are classified as "sub-rounded". The Kern River gravels are remarkably free from flat or elongated pebbles. The proportion of such pebbles in the \Vi- to %-inch size ranges from 5 to 7 percent. Ac- cording to the form classification described previously, all the Kern River gravels fall in the "equant" class. QUALITY OF MATERIALS AS DETERMINED BY ROUTINE LABORATORY TESTS Laboratory testing is used as a means of scientifically evaluating the suitability of aggregate material and is a valuable adjunct to the petrographic appraisal. Data resulting from tests conducted by state and federal agen- cies have been compiled and evaluated. Laboratory tests on samples taken from floodplain and terrace deposits of the Kern River and from the Kern River formation were performed by the U. S. Bureau of Reclamation prior to approval for their use in the Friant-Kern Canal and ap- purtenant irrigation works. The results of the tests, which are presented in table 4, are discussed below (U. S. Bureau of Reclamation, 1945, 1950, 1954). Standard acceptance tests are conducted periodically by the California Division of Highways, Materials and Research Laboratory, Sacramento, on material from com- mercial deposits in the Bakersfield area. Kern River ag- gregates have been used for many years on state high- ways. The results of their tests, which are summarized in table 3, indicate that these materials meet California standard specifications for concrete aggregate. For a discussion of the general requirements of aggre- gate materials, specifications, and descriptions of the tests commonly employed to evaluate material in the labora- tory, the reader is referred to the appendix. Gradation, Specific Gravity, Absorption, and Abrasion. The three types of deposits, where commercially de- veloped, differ in the proportion of coarse gravel present. The gravels are coarser in the Kern River formation (25 to 38 percent is plus 3-inch) than in the Quaternary terrace deposits (9 to 15 percent is plus 3-inch). The Recent floodplain, where commercially developed, con- tains finer materials and no gravel larger than 3 -inch. The pit-run gradations will vary at different locations in these deposits because the size of the particles depends upon the distance of transport from the mountain front. Gradations of unprocessed sand and gravel samples taken from commercially worked areas in the geologic forma- tions near Bakersfield are presented in table 5. The proc- essed sand all falls within grading specifications set up by the ASTM standard C33-54T for fine aggregate (ASTM, 1955, p. 1). The sand and gravel are above specification limits for specific gravity and have low absorptions. Abrasion losses in the Los Angeles Rattler tests on the gravel fraction are well below ASTM specifi- cation limits. The gravel samples from the Kern River formation had slightly higher losses, possibly due to the weathering effects previously discussed under the section on petrographic examination. 22 California Division of Minfs dood" and/or "satisfactory" 100% 5 o.EX CE LLE NT- f or use in concrete. 10% HIGHLY SUITABLE-for use in concrete SUITABLE-for the low-medium strength and abras- ion-resistance re- quirements of con- 30% crete in moderate c I i mates. As above, but usable only f better material is not economically available. UNSUITABLE. 15% 20% PHYSICAL QUALITY CLASSIFICATION AND COMPARISON DIAGRAM POOR 100% • ELL-ROUNDED 100% SUS-ROUNDEO ANO SUS-AHOULAR 100% ROUNDNESS CLASSIFICATION AND COMPARISON DIAGRAM Figure 3. Classification and comparison of physical quality and roundness of aggregates in the Bakersfield area. Numbers refer to samples taken from deposits in the Kern River floodplain (no. 1), Quaternary terraces (nos. 2, 3, 6), and the Kern River formation (nos. 4, 5). See plate 2 and table 1 for location and description of individual samples. Sand and Gravel Resources, Kern River Table 3. Results of standard acceptance tests on processed aggregate from commercial deposits in the Bakersfield area* 23 Soundness (wt. av. NajSC>4 percent loss) Specific gravity Absorption Abrasion (coarse aggregate) Organic Location of commercial deposit Fine Coarse Fine Coarse Fine Coarse 100 rev. 500 rev. contam- inants Kern River formation (NW of Bakersfield) 1 2 4.5-4.6 4.5 0.8-2.9 2.0 2.60-2.70 2.62 2.58-2.67 2.63 1.2-1.5 1.3 1.2-1.5 1.4 5.2-7.6 6.4 25.4-30.0 27.0 1 + Quaternary terrace (NE of Bakersfield) 1 2 3.2-4.8 4.0 1.4-3.7 2.7 2.59-2.64 2.63 2.59-2.64 2.64 0.9-1.5 1.3 0.7-1.1 1.0 7.0 7.0 26.8-27.4 27.1 1 + * Tests made by California Division of Highways, Sacramento. 1 Range of test results — number of tests varied from 3 to 15. * Average of test results. Table 4. Results of standard acceptance tests on unprocessed material from deposits of sand and gravel in the geologic formations near Bakersfield.* Type of test Recent floodplain Specific gravity Absorption percent Soundness (Wt. av. NajSOi percent loss) Abrasion 100 rev. Loss 500 rev. Organic content Sec. 1. T. 29 S., R. 29E., M.D Sand Gravel 2.65 0.8 2.5 1 + 2.66 0.6 2.0 24.5 Quaternary terrace Sec. 2, T. 29 S., R. 28E., M.D. Sand Gravel 2.63 0.8 4.3 1 + 2.64 0.9 2.3 6.3 27.3 Kern River formation Sec. 27, T. 28 S., R. 26E., M.D. Sand Gravel 2.63 0.8 4.1 1 + 2.64 1.2 5.4 7.5 31.1 * Data from U.S Bureau of Reclamation, (1945, 1957), tests C-268, C-268H. Table 5. Gradations of some unprocessed sand and gravel samples taken from commercially worked geologic formations near Bakersfield. Pliocene Recent Quaternary Kern River Floodplain 1 Terrace 2 Formation' Sec. 4, T. 29 S., Sec. 2, T. 29 S., Sec. 27, T. 28 S., R. 29 E. R. 28 E. R. 26 E. Gravel grading (combined 6* cumulative 3" 9 15 38 25 percent re- IVi" 25 15 32 54 46 tained) %' 36 16 41 64 60 %' 40 18 47 69 66 ] So. 4 43 21 51 72 70 Sand grading Percent sand 57 79 49 28 30 Cumulative #8 6 19 6 11 10 percent re- #16 29 58 27 33 33 tained #30 76 89 64 61 66 #50 82 96 87 82 83 #100 91 98 94 89 90 Pan 100 100 100 100 100 Percent silt in sand 3.3 1.6 4.1 2.5 2.0 1 Data from Smith-Emery Co. test. 2 Data from U.S. Bureau of Reclamation (1950), test C-268D. * Data from California Division of Highways test. Organic Content Test. Sand from the three types of deposits contains from 2.0 to 4.1 percent silt and requires washing; however, none of the sands contains harmful amounts of organic matter as indicated by the organic color test. Soundness (Sodium Sulfate) Test. The sodium sulfate soundness tests, which were performed by the Division of Highways on commercial deposits in the Kern River formation and in the Kern River terraces showed low losses within ASTM specification limits. The tests per- formed by the Bureau of Reclamation showed a slightly higher loss for the gravel in the Kern River formation. This higher soundness loss, as in the case of the higher absorption described above, is no doubt a reflection of the weathered character of this older formation. Soundness (Freeze-Thaiv) Test. Concrete cylinders made with sand and gravel from commercial pits in the Quaternary terrace and the Kern River formation were subjected by the U. S. Bureau of Reclamation (1954, 1957) to freezing and thawing durability tests. Alternate freezing and thawing was continued until the specimens lost 25 percent of their original weight or 1000 cycles were obtained. Results indicated that the concrete made with Kern River formation aggregates and containing 3.8 percent entrained air withstood 1,035 cycles with 11 percent weight loss. Concrete made with Quaternary terrace aggregate and 3.0 percent entrained air withstood 1020 cycles for a 21 percent weight loss. Both aggregates are considered to have excellent durability. Compressive strength was very good: 5260 pounds per square inch for the Kern River formation aggregate and 4510 pounds per square inch for the Quaternary terrace aggregate. Alkali Reactivity (Mortar-Bar Expansion) Test. Mor- tar-bar tests were made by the U. S. Bureau of Reclama- tion to determine if the sands and gravels from the Quaternary terrace deposits would react with alkalies in cement to produce deleterious expansion. After 6 months, test results showed maximum expansions of 0.047 percent for the sand and 0.030 percent for the gravel. Expansions were less than the 0.05 percent expansion limit at 6 months used by the American Society for Testing Ma- terials to denote potentially reactive material. Results of the mortar-bar tests are given in table 6. 24 California Division of Mines Table 6. Alkali aggregate reactivity test on Quaternary terrace deposit, sec. 2, T. 29 S., R. 28 E., M.D.* Mix parts by weight — 1 :2 . 00 Sealed in moist air at 100° F. Material Sand Gravel Cement no . _ 9406 7488 7488 7488 9406 7488 7488 7488 Equivalent soda, in cement, percent _ 0.17 1.19 1.19 1.19 0.17 1.19 1.19 1.19 Test aggregate, percent .. _ 100 100 50 25 100 100 50 25 50 75 50 75 Age Expansion — Percent** 1 month. . . —0.001 0.023 0.022 0.019 0.001 0.015 0.015 0.019 3 months - . — — .002 .038 .026 .025 — .004 .019 .020 .023 6 months .007 .047 .035 .031 .001 .028 .030 .027 * Data from U.S. Bureau of Reclamation, 1957, Rept. C-268H. ** Aggregates that have shown harmful reactions in concrete generally have produced expansions of more than 0.05 percent at 6 months. ECONOMIC POSSIBILITIES Volume of Available Material. Rough estimates as to the quantities of sand and gravel economically available in the Kern River floodplain and terrace deposits were made using data from plate 2, Aggregate resources of the Kern River near Bakersfield, on which the potential areas for developing concrete aggregate have been delineated. The estimates give only the order of size, as no drilling or geophysical work was done to determine the depth of the deposit. Those areas marked with the symbol "G" warrant exploration for aggregates of suitable to high quality because there is little or no overburden, the weathering effects are negligible to moderate, and there is satisfactory grading so that only a few percent of plus- 6-inch material is present. Assuming a depth of 30 feet, the distribution of this type of material is estimated at 70 million cubic yards in the Recent floodplain and 40 million cubic yards in the Quaternary terrace deposits. Other areas, marked with the symbol "F", are less favorable for exploration because of one or more of the following factors: fairly advanced weathering, excessive depth of sandy overburden, heavy tree growth, or oper- ating difficulties. However, they do constitute a potential source of satisfactory materials. Assuming a depth of 30 feet, the distribution of these materials is estimated at 40 million cubic yards in the Recent floodplain and 30 mil- lion cubic yards in the Quaternary terrace deposits. Those areas not warranting exploration are indicated by the symbol "P" on the map. Aggregate development in the Kern River formation requires detailed exploration including systematic drill- ing and sampling to delineate suitable areas. However, in general, there is little likelihood of development in the Kern River formation north of section 28, T. 28 S., R. 27 E., where it consists of fine material; or east of sec- tions 1 and 12, T. 29 S., R. 28 E., where it is believed to be too bouldery. These broad limits are indicated on plate 2. The Kern River formation on the south side of Kern River is unexploited except in the old Hartman pit (map no. 5). This pit is now in the Bakersfield city limits and was recently used as a source of road base by Thomas Construction Co. for the nearby highway interchange. By judicious integration of land development and proper pit exploitation, the Kern River formation can be a local source of aggregate for short sustained periods and offers possibilities for future exploitation. For example, material removed in the realignment of the China Grade road was hauled by the contractor to his sand and gravel plant and processed for aggregate. Commercial Production. The total recorded produc- tion of sand and gravel in the Bakersfield area from 1915- 60 amounts to about 10 million tons valued at about 12 million dollars. About three-fourths of this total was pro- duced in the period 1948-60. As a result of the post- World War II expansion in industry and building, annual production has steadily increased from a quarter of a mil- lion dollars in 1946 to over a million dollars in 1960. According to the 1960 returns of the U. S. Bureau of Mines, approximately 896,000 tons of sand and gravel valued at about $1,270,000 were produced in the Bakers- field area. About half of this production went into con- crete aggregate; the remainder into bituminous aggre- gate, road base, and fill. In 1960, three plants were operating in the Kern River formation, approximately 5 miles north of Bakersfield, and two plants were producing from Quaternary terraces 4 to 6 miles northeast of Bakersfield. The plants are lo- cated outside the city limits in areas where there are thick gravel layers without an excessive number of boulders, and little or no overburden. Sand and Gravel Resources, Kern River 25 - I Si > t I I G&Sw-r ■•«-* -Sfc^ 3 i ■M^^ < «**»=*.*- ^ " .'-. :, " Photo 10. Pit in the Kern River formation northwest of Bakersfield. The lenticular nature of the sandy overburden is shown as it increases abruptly from about 2 feet on the right to over 8 feet on the left. The mining and processing of sand and gravel de- posits in the Bakersfield area are performed very simply. Overburden, generally 1 to 3 feet in the Kern River for- mation and 6 to 12 feet in the terraces, is stripped off by bulldozer, and the sand and gravel are excavated by power shovel or dragline. End-dump trucks are used to trans- port the materials to the processing plant, ordinarily a maximum distance of several hundred feet. Selective quarrying methods are used in some pits to avoid caliche deposits near the surface of the Kern River formation and to eliminate areas that contain coatings on the gravel. The processing plants generally consist of a primary jaw crusher, secondary roll or cone crushers, standard vibratory screens, and wheel or screw-type sand classi- fiers. Descriptions of the commercial operations are sum- marized in table 7. The plants in the terrace deposits are located where 6-inch gravel is about the maximum size. The plants in the Kern River formation process materials up to 12-inch size; a considerable portion of the crushed oversize goes into bituminous mixes. Gold has also been produced in significant amounts as a by-product by sand and gravel operators from ter- races and floodplain deposits of the Kern River. Between 1935 and 1957, 2470 ounces of gold and 463 ounces of silver valued at $87,180 were produced. The gold was removed from the sand fraction in the washing process by means of riffles. The gold content ranged from 6^ to 26^ a cubic yard. Marketing. The present market for sand and gravel produced in the Bakersfield area includes portions of Kern and Tulare Counties. Producers in the Kern River formation northwest of Bakersfield distribute material as far north as Delano (32 miles) and Wasco (27 miles). Producers in the terrace deposits northeast of Bakersfield market material in and around the city of Bakersfield. In the past, capacities of the plants in the Kern River formation were comparatively small and enough material was processed to supply company-owned outlets. Two of the companies also operated plants in the terrace deposits. Recently these terrace plants were shut down and new plants were built 40 miles to the south on the north flank of the Tehachapi Range on Salt-Tecuyah and San Emig- dio Creeks. The new plants, which have comparatively large capacities, are designed to supply material to con- crete-pipe manufacturers and oil companies in the south end of the valley, and to company-owned ready mix con- crete plants in Bakersfield. The 40-mile haul is an addi- tional expense to these operators because the aggregate is hauled by independent truckers under rates set by the I.C.C. Therefore, to compete in the Bakersfield market, the Tehachapi producers have an integrated setup of company-controlled distribution from the pit to the con- sumer of readymixed concrete. In 1958 ready mix con- crete sold for $12 a cubic yard in Bakersfield irrespective of where the aggregate was mined. Sj«&:-t' ^^sfc ^Hek"-- •-■• Photo 11. Left, Dicco Inc. sand and gravel plant northwest of Bakersfield. Bituminous aggregate is produced at this plant. Above, Dicco Inc. pit in the Kern River formation furnishes the raw mate- rial for their nearby plant. The oil wells in the background are situated on the topographic ex- pression of the Kern arch. Photo 12. Below, Cal Rock Com- pany (Rinker Rock Co.) plant north- west of Bakersfield. Material from a nearby pit is processed for use as concrete and bituminous aggre- gate and road base. Right, Cal Rock Co. pit in the Kern River formation. Sand and gravel are excavated by dragline, loaded on end-dump trucks, and hauled to the plant for processing. Note the prox- imity of pit operation to oil field derricks and pumps. W f jL- Photo 13. Top, Kern Rock Co. plant northwest of Bakersfield. Concrete aggregate is produced from material obtained at a nearby pit. Left, above, Kern Rock Co. pit in the Kern River formation. Windrows are composed of the wasted overburden. Photo 14. Left, below, Kern River Rock Inc. (River Rock Co.) pit in the Quaternary terrace provides material for their plant. Right, above, Kern River Rock Inc. (River Rock Co.) plant northeast of Bakersfield. The raw material is processed for use as concrete and bituminous aggregate. Si? < ■ .-.-.- '•*&&** ^ / . fJ <*' ^•w* ' ~, 28 California Division of Mines Table 7. Commercial sand and gravel producers in the Bakersfield area in 1960. Name Location S. T. R. Geology of deposit Plant data Products Reported capacity 1958 Remarks Griffith Co. P.O. Box 175 Bakersfield NW 29S 28E Kern River Quaternary terrace, interbedded pebble-cobble gravel lenses up to 3 feet thick with sand lenses up to 8 feet thick. Diamond jaw-primary crusher; secondary cone crushers; revolving trommel washer; sand wheels, standard vibra- tory screens. Asphalt plant. Portable readimix plant. Concrete aggregate, bituminous aggregate, fill. Dry-175 tons/hr.; wet-125 tons/hr. Overburden 8 to 10 feet. For asphaltic mix, strip caps off hills in Kern River formation. Kern River Rock Co P.O. Box 506E Oildale 35 28S 28E Kern River Quaternary terrace; highly lenticular cobble to boulder lenses up to 6 feet thick; sand inter- beds from 6-12 feet thick. Primary jaw crusher, secondary roll crusher, Eagle screw sand classifier, standard vibrating screens. Concrete aggregate, bituminous aggregate. 500 tons/ day Overburden 6 feet of sand. Encounter water at 30 feet below surface. Bin 217 Station A Bakersfield 28 28S 27E Kern River formation. Cobble-boulder conglom- erate 6-8 feet thick with sand lenses 1-3 feet thick. Maximum size 12-inch boulder. Primary jaw crusher, cone crushers; standard vibratory screens; Eagle sand screw. Bituminous aggregate. Estimated 75 tons/hr. Overburden 1-2 feet sand. Kern Rock Co P.O. Box 1697 Bakersfield 27 28S 27E Kern River formation. Cobble conglomerate layer 10-15 feet thick. Maximum size 6- to 8-inch cobble in sand matrix. Primary jaw, secondary symons cone. Trommel screen, vibrating screens, sand wheels. Concrete aggregate. 75 tons/hr. Overburden 1-2 feet sand. Rinker (Cal Rock Co.) P.O. Box 810 Bakersfield 27 28S 27 E Kern River formation. Cobble-boulder conglom- erate layer 10-15 feet thick. Maximum size gravel 8- to 12-inch in sand matrix. Primary jaw, secondary cone, four vibratory screens, sand screw. Concrete aggregate, road base. 300 tons/hr. Overburden 1-2 feet sand. Operators located in the terraces (and in the past in the Recent stream bed) northeast of the city have haul distances equal to those of operators in the Kern River formation. All hauls from either locality are over State Highway routes, so that there is no problem of hauling over restricted city streets with specified load limits. The operators in the terrace deposits use the materials on their own jobs or sell to company-owned ready mix concrete plants. As the terrace deposits are deficient in gravel sizes, occasionally additional gravel is purchased from produc- ers in the Kern River formation. Photo 15. Griffith Construction Company plant northeast of Bakersfield at which concrete and bituminous aggregate are produced. Zoning and Leasing. The commercial plants are all now located outside the city limits of Bakersfield to avoid the usual zoning restrictions placed upon sand and gravel plants in urban areas. While it may be possible to obtain a quarry permit within a city, strict regulations controlling operational procedures are ordinarily im- posed, including restricted hours of operation, noise and dust control, limited haul routes, and load and speed limits. In addition, gravel operators would ordinarily have to maintain goodwill in a community by fencing open pits, camouflaging plants, or restoring unsightly excavations. Even the ready mix concrete plants, which are located in heavy industrial zones away from residen- tial property, abide by strict ordinances. A substantial portion of the surface extent of the Kern River formation overlies producing oil fields and is con- trolled by oil companies who own the mineral rights. The location of the sand and gravel pits is governed by the oil companies who ordinarily will grant leases with- out difficulty provided that the sand and gravel operator does not interfere with the pump or derrick operations in the oil field. The Kern Rock Co. pit is in the Kern Front oil field amidst the derricks and pumps, while the Dicco Inc. and Rinker Rock Co. pits are only a quarter of a mile from the derricks. Development of the terrace deposits is less hampered by the oil-field operations, al- though the original discovery well of the Kern River field is in the terrace deposit near Griffith Company's pit. Sand and Gravel Resources, Kern River 29 Photo 16. Above, Griffith Construction Company pit in a Quaternary terrace near their plant (in background). Below, Close-up of gravel in the pit. A small part of the suitable terrace deposits lies within the boundary of the Kern River Park and is therefore excluded from exploitation. Future. Continued growth in population and result- ant demands for materials to build roads, homes, stores, churches, theatres, hospitals, industrial and municipal facilities will sustain demand for sand and gravel in the Bakersfield area. The new Federal Highway program will of necessity require large quantities of concrete and bituminous aggregate, and road base in addition to that which is used in the present road-building program. At the present time, because of the absence of gravels in the valley west of Highway 99, sand treated with ce- ment is used as sub-base on roads. Should specifications be tightened up to require the use of coarse aggregate for sub-base, a new market would be created as, of ne- cessity, these materials would come from the gravel de- posits in the Kern River area. Many new public works projects are proposed for the west side of the San Joaquin Valley, including a new state highway, and canals and pumping plants of a large aqueduct along the west side of the valley. With in- creased importation of water, irrigation distribution work and associated community developments will also demand more aggregates, particularly for concrete pipe. These activities will require significant amounts of con- crete and bituminous aggregate which the Bakersfield producers will be in a competitive position to furnish. • Zr&# ^ 30 California Division of Mines Photo 17 (upper left). Grading machine used to determine the par- ticle-size distribution of coarse aggregate. The sample is mechanically separated into decreasing sizes. Photo 18 (upper right). The distribu- tion of fine aggregate is determined by use of mechanical sieve shakers such as shown in the photograph. The sand is separated into fractions on sieves of decreasing size openings. Photo 19 (lower left). Los Angeles Abrasion machine (L.A. Rattler). Toughness and resistance to abrasion are determined with this machine. The coarse aggregate and metal balls are placed in the cylinder and revolved at a pre- determined speed and for a specified number of revolutions. Photo 20 (lower right). Equipment used to perform the California Division of Highways sand equivalent test is pictured above. This test provides a rapid determination of the ratio of sand to clay-like material in the fine aggregate. Photos by Mary Hill. APPENDIX Standard Laboratory Acceptance Tests To be suitable, an aggregate has many requirements that are difficult to meet if only unprocessed material from natural deposits is used. Suitable material is com- posed of clean, uncoated, properly shaped particles which are sound and durable. Soundness and durability are used to denote the ability of aggregates to retain a uniform physical and chemical state over a long period of time so as not to cause disruption of the concrete when exposed to weathering and other destructive proc- esses. To have these attributes, individual particles must be tough and firm, possessing the strength to resist stresses and chemical and physical changes such as swell- ing, cracking, softening and leaching. The aggregate should not be contaminated by much clayey material, silt, mica, organic matter, chemical salts, or surface coatings. In addition to containing particles which are individ- ually sound and durable, the deposit should contain an over-all assemblage of particles which can be processed to obtain the proper size grading. The grading of con- crete aggregate has very pronounced influence on the workability of the concrete mix and the proportion of cement and water needed to produce high-quality con- crete. The geological and engineering aspects of an investi- gation of alluvial deposits to evaluate their suitability for aggregate has been covered in numerous articles, some of which are given in the list of references. For a brief re- view of the subject the reader is referred to the article Sand and Gravel for Concrete Aggregate, by H. B. Goldman, in the January 1956 issue of the California ]ournal of Mines and Geology. Laboratory testing is a means of scientifically evaluat- ing the suitability of aggregate material. In an attempt to forecast the behavior of the aggregate in concrete, numerous tests have been devised, many of which are complicated and require expensive equipment and trained technicians. Several of these tests have been used for many years and are familiar to those in concrete construction work. A strong effort is being made to standardize testing procedures throughout the nation and many laboratories use, with little or no modifications, test methods as set forth in detail by the American So- ciety for Testing Materials. The principal tests per- formed on aggregates are for toughness and abrasion re- sistance, soundness, organic content, grading, specific gravity, absorption, and alkali-aggregate reactivity. Pet- rographic examination supplements the laboratory tests. Toughness and resistance to abrasion are determined by abrasion tests, such as the Los Angeles Rattler * and wet shot tests. Los Angeles Rattler Method. The Los Angeles Rattler method is used to determine the resistance of mineral aggregate to com- bined impact and abrasion in a rotating cylinder containing me- tallic spheres. The procedure consists of placing a graded and weighed sample in a metal cylinder 28 inches in diameter and 20 inches in height with 6 to 12 iron or steel spheres approximately 1% inches in diameter, each weighing about 1 pound. The ma- chine is rotated about a horizontal axis at a speed of 30 to 33 rpm. for 100, 500, or 1,000 revolutions, after which the sample is re- moved, resieved, and reweighed. The difference between the original and the final weight of the test sample is expressed as a percentage of the original weight and reported as the percentage of wear. Wet Shot Method. The wet shot test is conducted in a manner similar to the Los Angeles Rattler test, except that water is present in the cylinder. Soundness of aggregates is determined by two methods: the quick sodium sulfate (or magnesium sulfate) test, or the slower freeze-thaw test. Sodium Sulfate (or Magnesium Sulfate) Soundness Test. The soundness of aggregates is determined by a quick test-method which measures the resistance of aggregates to disintegration by the force of crystallization of salts absorbed from saturated solu- tions of sodium or magnesium sulfate. The procedure involves sieving and weighing the samples, immersing desired size-gradings in prepared hot solutions of these salts for 16 to 18 hours, remov- ing and drying, and then repeating the entire cycle. After the final cycle, the samples are washed, dried, resieved and reweighed. The weighted average percent loss is then calculated from the percentage of loss for each fraction. The fraction larger than %-inch is examined visually to detect any disintegration, splitting, crumbling, cracking, flaking, etc., caused by crystal growth in the fractures, pores, and capillaries. Freeze-Thaiv Test. The freeze-thaw method consists of mix- ing the aggregate sample with a standard mixture of cement, entrained air, and water to form test beams. These beams are cured and then subjected to cycles of freezing at 0° C and thaw- ing to 40° C. The change in the dynamic modulus of elasticity is measured periodically by sonic equipment (electronically). Durability is judged by the percent change in the modulus of elasticity with continued cycles of freeze-thaw. This method has the disadvantage of being much slower that the sodium sulfate (or magnesium sulfate) test. Organic Content. The organic impurity in the finer fractions of the aggregate sample is determined by a color test using a 3 percent sodium hydroxide solution. A specified amount of the sample is placed in a container with the solution, agitated and allowed to stand 24 hours. The color of the liquid is then de- termined by electric colorimeter and compared with a standard- color solution of tannic acid, alcohol, and sodium hydroxide. Size and Grading. The determination of the particle-size dis- tribution of aggregates is a standard laboratory procedure which involves the use of sieves. The sample is weighed and run through nested sieves of progressively finer mesh openings, vibrated either mechanically or by hand. The size fraction that accumulates on each sieve is then weighed and the results are reported variously as total percentages passing each sieve, as total percentages re- tained on each sieve, or as an artificial number called the "fine- ness modulus". The fineness modulus is obtained by adding the cumulative percentages retained on the #100, 50, 30, 16, 8, 3% inch, 1 Vi inch, and 3-inch sieves, and dividing by 100. Specific Gravity and Absorption. Specific gravity and absorp- tion are utilized as a basis for designing concrete mixtures and are also important in determining the quality of the aggregate. The test procedure consists of weighing the water-saturated sample both in air and in water, and again after it has been oven- dried. Absorption and specific gravity are then calculated, using the results of the weighings. Specific gravity is expressed by the ratio of the weight of a given volume of aggregate to the weight 32 California Division of Mines of an equal volume of water. Absorption is expressed as a per- cent ratio of the weight of moisture absorbed to the dry weight of the material. Sand Equivalent. The California Division of Highways has recently adopted a test to determine the effective volume of detrimental fine dust or clay-like materials in fine aggregates (California Standard Specifications, 1954, p. 26). The test is per- formed by shaking, using a prescribed technique, a known volume of the sample in a glass cylinder with a water solution of calcium chloride, glycerine, and formaldehyde. The mixture is permitted to stand 20 minutes and the relative volume of the clay and sand is then measured. The sand equivalent is the ratio of the volume of sand to the volume of clay and is expressed as a whole number. The higher the number the lower the clay content. Alkali Reactivity Tests. Alkali-aggregate reactivity has been discussed at length in many publications (Goldman, 1959; Mer- riam, R., 1953). A reactive aggregate is any rock, gravel or sand that contains one or more constituents that react chemically with the alkalies (sodium and potassium) in some types of portland cement. This reaction, which may result in expansion, cracking and deterioration of concrete, arises from osmotic pressures pro- duced by the formation and hydration of alkali silica gels. The gels are formed through interaction between the mineral aggre- gate and the alkalies which are liberated by the cement during hydration (McConnell et al, 1950, p. 234). Opal (amorphous hydrous silica) is the most widespread aggregate material react- ing in this manner. Other rocks and minerals known to be re- active are: glassy volcanic rocks, some chalcedonic rocks, certain phyllites which contain a hydro-mica, and the minerals tridymite, heulandite, and certain other zeolites. Any rock containing a significant proportion of reactive substances may be deleteriously reactive; thus normally non-reactive sandstone, shale, basalt, gran- ite, and other rock types may be harmful if impregnated or coated with opal, chalcedony, or other reactive substances. There are several approaches to the determination of harmful quantities of chemically reactive impurities in aggregates. Petro- graphic examination for physical and chemical properties has been mentioned previously. During such examinations the petrog- rapher is alert. for the presence of constituents that may be chem- ically unsound. By using the petrographic microscope one can readily identify reactive ingredients such as opaline silica, chal- cedony, and volcanic glass, and estimate the quantity present. On the basis of petrographic observations, aggregates containing suspected reactive materials can be subjected to such substantiating laboratory tests as the mortar bar expansion test and the chemical method of determining potential reactivity. In the mortar bar expansion test the test aggregate is sieved and mixed with cements of known alkali content to form 1-inch by 1-inch by 10-inch mortar bars. These are cured under labora- tory conditions of controlled temperature and humidity for speci- fied lengths of time, usually 1 to 2 years. Periodically the lengths of the bars are measured and the reactivity expressed as the per- centage of expansion in a given length of time. The excessive length of time required to perform this test has led to the estab- lishment of a quick chemical test. The quick chemical test for determining potential reactivity of aggregates is based on the degree of reaction of the aggregate with a sodium hydroxide solution under controlled laboratory test conditions. The procedure as described by Mielenz (McCon- nell et al., 1950) involves digesting a pulverized sample of the material in a sodium hydrdoxide solution and filtering the mixture. A portion of the filtrate is analyzed to determine the amount of dissolved silica. The alkalinity of the balance of the filtrate is determined chemically by comparison with a solution of known acidity. The amount of dissolved silica and the reduction in alkalinity are used as a measure of the potential reactivity. General Specifications for Concrete Aggregate The study of the results of laboratory tests on ag- gregates that have good service records in concrete has led to the establishment of certain minimum require- ments or specifications to which aggregates are expected to conform. These specifications are designed so that completely serviceable concrete will be made, if any aggregate that meets the requirements is used. Most specifications written by government agencies, engineer- ing societies, and concrete technologists attempt to con- form to one standard set of specifications— those set up by the American Society for Testing Materials; but mod- ifications of these standards for certain types of concrete work make it difficult to compare individual require- ments of the various organizations. Therefore it is a diffi- cult task to evaluate the suitability of a deposit by judg- ing the test results of selected samples. Some deposits which may not meet certain required specifications may have to be utilized because of other outside factors, such as the greater expense of hauling a more suitable aggre- gate. In general, aggregate from an untried deposit will be satisfactory for most uses if it meets the following mini- mum standards (these specifications are a general average of the basic requirements recommended by the ASTM, California Division of Highways, U. S. Army Corps of Engineers, and the U. S. Bureau of Reclamation). Abrasion— The abrasion loss should be less than 30 percent. Soundness— The loss in the sodium sulfate test should be less than 10 percent. Specific Gravity— The specific gravity should be greater than 2.55. Size and Grading — a. The deposit has proper grading so that the fine aggregate should contain no more than 45 percent of the material be- tween two consecutive sieve sizes. b. The fineness modulus should be between 2.3 and 3.1. c. No more than 5 percent of the material should pass the No. 200 sieve. Reactivity— A mortar bar containing the aggregate should have an expansion less than 0.10 percent in one year with a 0.8 percent alkali content cement. Absorption— The absorption should not exceed 3 percent. Durability— The concrete containing the aggregate should not have a loss in the modulus of elasticity exceeding 50 percent in the freeze-thaw test. Sand Equivalent— The fine aggregate should have a sand equiva- lent of not less than 75. REFERENCES American Society for Testing Materials, 1954, ASTM standards on mineral aggregates, concrete, and nonbituminous highway materials. Anderson, F. M., 1905, A stratigraphic study in the Mount Diablo range of California: California Acad. Sci. Proc, 3d. ser., vol. 2, p. 187-188, 191. California Division of Highways, 1954, California standard speci- fications, p. 178-182. Corps of Engineers, U. S. Army, 1949, Handbook for concrete and cement. Frink, J. W., and Kues, H. A., 1954, Corcoran clay-a Pleisto- cene lacustrine deposit in San Joaquin Valley, Calif.: Am. Assoc. Petroleum Geologists Bull., vol. 38, no. 11, p. 2257-2371. Goldman, H. B., 1956, Sand and gravel for concrete aggregate: California Jour. Mines and Geology, vol. 52, no. 1, p. 79-104. Goldman, H. B., 1959, Franciscan chert in California concrete aggregates: California Div. Mines Special Rept. 55. Klein, I. E., and Goldman, H. B., 1958, Sand and Gravel re- sources of Cache Creek: California Jour. Mines and Geology, vol. 54, no. 2. Knopf, A., 1918, A geologic reconnaissance of the Inyo Range and the eastern slope of the southern Sierra Nevada, California: U. S. Geol. Survey Prof. Paper 110, 130 p., pis. 1, 2, [maps, scale 1:125,000]. Knopf, A., and Thelen, P., 1905, Sketch of the geology of Mineral King, California: California Univ. Dept. Geol. Sci., Bull. 4, p. 227-262, pi. 30 [map, scale 1:125,000]. Krumbein, W. C, and Pettijohn, F. J., 1938, Manual of sedi- mentary petrography, D. Appleton-Century Co. Inc., New York, London, p. 277-302. McConnell, D., Mielenz, R. C, Holland, W. Y., and Greene, K. T., 1950, petrology of concrete affected by cement aggregate reaction: Geol. Soc. America Mem., Berkey vol., p. 234. Merriam, R., 1953, Alkali-aggregate reaction in California con- crete aggregates: California Div. Mines Special Rept. 27. Mielenz, R. G, 1946, Petrographic examination of concrete ag- gregates: Geol. Soc. America Bull., vol. 57, p. 310-312. Mielenz, R. C, 1954, Petrographic examination of concrete ag- gregate: Am. Soc. Testing Materials Proc, vol. 54, p. 1188-1217. Miller, W. J. and Webb, R. W., 1940, Descriptive geology of the Kernville quadrangle, California: California Jour. Mines and Geology, vol. 36, no. 4, p. 343-378, pi. 2 [map, scale 1:125,000]. Rhoades, Roger and Mielenz, R. C, 1946, Petrography of con- crete aggregates: Am. Concrete Inst. Jour., vol. 17, p. 581-600. U. S. Bureau of Reclamation, 1945, Laboratory tests of concrete aggregate— Friant-Kern Canal— Central Valley Project: U. S. Bur. Reclamation, Laboratory Rept. no. C-268, Denver, Colo. U. S. Bureau of Reclamation, 1950, Laboratory tests of con- crete aggregate— Friant-Kern Canal— Central Valley Project: U. S. Bur. Reclamation, Laboratory Rept. no. C-268 D, Denver, Colo. U. S. Bureau of Reclamation, 1955, Concrete manual, Denver, Colo., 6th ed., p. 1-187. U. S. Bureau of Reclamation, 1957, Laboratory tests of concrete aggregate— Friant-Kern Canal— Central Valley Project: U. S. Bur. Reclamation, Laboratory Rept. no. C-268H, Denver, Colo. Webb, R. W., 1946, Geomorphology of the middle Kern River basin, southern Sierra Nevada, California: Geol. Soc. America Bull., vol. 57, no. 4, p. 355-382, pi. 7 [map, scale 1:125,000]. Webb, R. W., 1950, Volcanic geology of Toowa Valley, southern Sierra Nevada, California: Geol. Soc. America Bull., vol. 61, no. 4, p. 349-357, pi. 1 [map, scale 1:60,000]. A 47746 8-61 3,500 printed In California state printing offici .< w SPECIAL REPORT @;f::f:;::: m~^~ Geology comp.fed by H Goldmon in 1956 from published mops b ond WeOB.R W.H9401, Knopl.A and Thelen P., (1905), Knopf, A, t 11946 I, Webb, R W. , U9S0), ond unpublished mop by Dibblee , 1 1952 1 GENERALIZED GEOLOGIC MAP OF THE KERN RIVER DRAINAGE AREA DIVISION OF MINES IAN CAMPBELL, CHIEF STATE OF CALIFORNIA DEPARTMENT OF NATURAL RESOURCES GEOLOGIC MAP SHOWING AGGREGATE RESOURCES OF THE KERN RIVER NEAR BAKERSFIELD