UC BERKELEY MASTER NEGATIVE STORAGE NUMBER 03-67.78 (National version of master negative storage number: CU SN03067.78) MICROFILMED 2003 UNIVERSITY OF CALIFORNIA AT BERKELEY LIBRARY PHOTOGRAPHIC SERVICE REPRODUCTION AVAILABLE THROUGH INTERLIBRARY LOAN OFFICE MAIN LIBRARY UNIVERSITY OF CALIFORNIA BERKELEY, CA 94720-6000 COPYRIGHT The copyright law of the United States (Title 17, United States Code) governs the making of photocopies or other reproductions of copyrighted materials including foreign works under certain conditions. In addition, the United States extends protection to foreign works by means of various international conventions, bilateral agreements, and proclamations. Under certain conditions specified in the law, libraries and archives are authorized to furnish a photocopy or other reproduction. One of these specified conditions is that the photocopy or reproduction is not to be "used for any purpose other than private study, scholarship, or research." If a user makes a request for, or later uses, a photocopy or reproduction for purposes in excess of "fair use," that user may be liable for copyright infringement. University of California at Berkeley reserves the right to refuse to accept a copying order if, in its judgment, fulfillment of the order would involve violation of copyright law. Hofer, F. M. Geological study of a portion of the Mt. Diablo quadrangle 1911 Berkeley, CA 245 10 Geological study of a M. Hofer and C. M. Staples. 260 Sc1911]. C. M. University of California at Berkeley Library Master negative storage number: (national version of the master negativ 03-67.78 e storage number: CU SN03067.78) 300 [31 p.] :8bill., col. maps :$c29 cm. 502 Thesis (B.S. 1911. 504 Includes bibliographical references. BIBLIOGRAPHIC RECORD TARGET GLADIS NUMBER: 184788207D FORMAT : BK LEVEL:b BLT:am DCF:a CSC:4d MOD: EL:7 CP:cau L:eng INT: GPC: BIO: FIC: PC:s PD:1911/ REP: CPI: FSI: 040 CUScCU 090 $bDISS.HOFER.GEOL 1911 610 20 University of California, Berkeley.S$bDept. Geophysics$xDissertations. 690 0 Dissertations, Academic$xUCBSxGeology$y1911-1920. 700 1 Staples, AD:991012/FZB UD:030604/MAP CON: ARCV: TLC: 11:0 portion of the ML. Diablo quadrangle /$clbyl] F. in Geology)-- University of california, Berkeley, May of Geology and Microfilmed by University of california Library Photographic Service, FILMED AND PROCESSED BY LIBRARY PHOTOGRAPHIC SERVICE, UNIVERSITY OF CALIFORNIA, BERKELEY, 94720 DATE: 08/03 REDUCTION: 10 X Thesis for B. 8S. Degree. Geological study of a Portion of the Mt. Disblo Quadrangle. ® Y n n T d 1] 1] x D by! 2 L LOI AAV 2.9 Thesis: "GEOLOGICAL STUDY OF A PORTION OF THE . : MT. DIABLO QUADRANGLE. LIBRARY COPY ey, 19) F. M. Hofer. C. M. Staples. Introduction. The original object of this thesis was to work out the geology of a portion of the Mt. Diablo quadrangle, especial- ly with relation to a deposit of Cinnabar which was exploit- ed a number of years ago. Owing to inclement weather, how=- ever, the preliminary work of topography, mapping, etc., re- quired so much time that it was impossible to do more than to work out the structure of the country, and to study to some extent the rocks making up the region. One day was spent in looking over the country in a gen- eral way in November, 1910. In January, 1911, eighteen days were spent in the field. The topographic work was the first object of this trip. Owing to bad weather at this time, the work of surveying was so delayed as to make it impossible to do any geological mapping during this trip; some specimens were collected, however. The next trip was made in March, 1911, and occupied one week. This time was devoted to geological mapping, collect- ing of specimens, etc. In several cases, lack of time pre- vented as accurate mapping as would have been desired. Since the district is a considerable distance from the University, the work was somewhat handicapped by the time required to make the trip. A full day was lost either way, and for this reason it was impossible to make frequent visits to the dis- trict. A number of thin sections have been made, both after the January trip, and after the March trip. These have been exduined as a check upon the field determinations. A final visit was made on April 22, 1911, in company with Prof. Louderback, to check up results and clear up any points left in doubt by the former trips. Location. The district studied lies in section 29, Tp. 1, N., R. 1 E., Mt. Diablo Meridian. It occupies an area of about one-half square mile in the center of the quadrangle. It is about four miles by wagon road from Clayton, Contra Costa County, and about sixteen miles from Antioch, in the same county. Topography. The principal topographical feature is a canyon, flank- ed on either side by a ridge. Toward the lower end this can- yon broadens out. The ridges are steep, particularly the one on the South, where there are several cliffs, formed by outcrops of chert and sandstone. (See Figures 1, 2, 3.) The North ridge, as a whole, presents a characteristic landslide topography. Along the flank facing the creek there are several slides; these appear on the map as benches. (See Figures 4, 5.) One is apparently of very recent date, as the face of the slide is still very steep and has not been covered by vegetation. Along the top of the ridge is a trough, which in one place deepens to a closed basin; this is also apparently due to sliding. IE RAS Figure 2. Figure 1. Figure 3. Figure 4. Figure 4. General Geology. The most extensive formation is a compact clay shale, which extends in a narrow belt along the creek, spreading out at the eastern end of the map, and filling the Horth- east portion. The belt also widens at the upper end of the creek, and swings around to the North. In the North- east, the shale has in it a body of yellowish brown sand- stone. The shale lies at a very constant attitude, with a dip of 35° to 80° to the North. It is soft and does not stand well under erosion. A noticeable feature of the top- ography determined by the shale is the presence of two sad- dles in the North ridge, where the shale crosses. The shale is best shown in the creek bottom, where the sand and boulders of the creek have been removed; here its attitude is easily observed. Its presence is shown, however, by the peculiar soil which it yields. This soil is marked by small fragments of the shale covering its entire surface, and there is little difficulty in tracing the formation by this means. The shale is thin-bedded, and blue-gray in color. There are occasional lenses of sandstone found in it, and frequent lenses of hard limestone. The latter are usually two to four inches in thickness, while the sandstone lenses are somewhat thicker. There are also occasional concretions. In this limestone there are found fossils which, we are informed, are characteristic of the Lower Cretaceous. They comprise bivalve shells, and these are found in abundance at the base of the Knoxville shales. Upper end of the North ridge showing the sad- dle formed by shale. Lower end of the North ridge. A large bed of sandstone is found with the shale, mak- ing up the point of the North ridge. This sandstone is thick=-bedded, even textured, and yellowish brown in color. The bedding planes are not prominent. It is rather soft, fine grained, and contains a great deal of mica. It con- tains also a large amount of quartz, and considerable limo- nite; the quartz grains are well rounded. This sandstone is conformable to the shale. Next in extent, of the sedimentary formations, is a radiolarian chert. This covers the highest portions of both ridges, and is found in isolated fragments in other parts of the region. The chert is prevailingly red in color. It is in beds of one to four inches in thickness, intercalated with thin beds of red, thinly laminated, silicious shale. These shale layers are one-quarter to one-half an inch thick, rarely as thick as one inch. The chert is full of vein quartz, the veins normally being thin, seldom as thick as one-tenth of an inch. They apparently never extend through the shale laminations, but often stop short at the surface of the shale. The radio-~ laria appear under the microscope as small round dots, ap=- parently consisting of secondary quartz, having a radial structure. In some places the chert is green instead of red, and in such cases the shale 1s not so marked as in the red var- iety. Otherwise it is no different, the characteristic veining being the same. There is also a light colored var=- iety, probably due to the leaching of the iron. The chert, where unaltered, is usually very badly dis- integrated at the surface, and is somewhat contorted, mak- ing its prevailing attitude, as a rule, very difficult to obtain. On the steeper slopes of the cherty ridge, frag- ments of the red chert are strewn down the slope, and the soil is everywhere full of smaller fragments. (See Fig. 6,7.) The chert area on the north side of the creek is heav- ily covered with greasewood, which is not found to any ex- tent in any other part of the map, and appears to be char- acteristic of the unaltered chert area. (See Figure 8.) Nearly all the chert on the south side of the creek, and part of that on the north side, is more or less alter- ed. When the alteration is carried to its full extent, the chert is changed to a white, hard, crystalline quartzite, with little, or none, of the original chert remaining. There are all gradations from the red chert to the holo- crystalline quartzite. The least altered phase shows sim- ply increased veining, the quartz veins being larger and more numerous. The greater part of the altered rock is largely quartz, with occasional pieces of the original chert. The alteration has apparently progressed farther in the chert at the west end of the map. Here very little of the original chert is found. In this part, also, there is sometimes found a black variety, due to the concentration of manganese. Here, and elsewhere, are found fragments of Figure 6. Figure 8. En i { Cliff of altered chert on South ridge. Looking toward the above AR — Cliff of altered chert on South ridge. Looking toward the above other varieties, due to different types of alteration. Associated with the chert is a dark gray, or black, sandstone. This is very hard, and has, at first sight, more the appearance of an igneous rock than of a sand- stone. It is fine grained, and composed of quartz grains, with occasional fragments of feldspar, and considerable dark material; the quartz grains are not well rounded. It contains, also, occasional veins of secondary quartz, simi- lar to those found in the chert. This sandstone, like the yellowish brown sandstone found with the shale, is thick-bedded, and the bedding planes are not prominent. It is probably older than the chert, but the relation between them was not wholly deter- mined. In some places the sandstone is apparently altered to a schistose rock. Where badly weathered, it is lighter in color. Intrusive into the chert and sandstone is a fine grain- ed greenstone. This contains abundant chlorite, in places, and occasional veins of albite. Certain portions are amyg- daloidal, the amygdules being filled with calcite. The alteration of the chert to quartzite is usually found to be associated with the greenstone. The latter weathers more readily than does the chert, or the black sandstone, and though it forms ridges, they are not so steep, nor so rugged, as those occasioned by the former. The evidences that the greenstone is an intrusive are, its irregular distribution with reference to the chert and sandstone, and the presence of isolated patches of chert and sandstone in the greenstone areas. A dike of serpentine is found in the western part of the map. This is exposed in three places, and in exposures of varying width. The serpentine appears to be a later in- trusive than the greenstone, as it cuts the latter in sev- eral places. It is rather badly decomposed, as a rule, and in only one place, the most eastern of its outcrops, does it make any prominent point. It may, however, be readily traced by its soil, which is a peculiar, white soil. Under the microscope, the serpentine shows a mesh structure, indicating that it is derived from olivine. There are several springs along the creek, and they appear to be determined by the impervious shale. The wat- er from several of these is strongly impregnated with hy- drogen sulphide. The rocks in this vicinity are somewhat altered by the action of the springs. (See Figure 9.) a oO 5 = a0) ord Pry Ey Structure. On examining the map, the most prominent feature is the south line of the clay shale. This is a regular line, having a definite relation to the attitude of the shale, and is evidently the true contact line. The shale, then, rests upon the rocks to the South of it. These are somewhat varied, and the shale is found to rest impartially upon chert, greenstone, and serpentine. The only explanation for this is that the shale rests upon a deeply eroded surface of the earlier rocks. The greenstone and the serpentine, which are both in- trusive into the chert and sandstone, are evidently not in- trusive into the shale. There is, in the shale, no indi- cation of the somewhat intense alteration and metamorphism which ie noticed in the chert and sandstone. Furthermore, were the rocks in their present relation at the time of the intrusion, it is probable that the soft and less resistant shale would be the location of most of the intrusive action. All these things seem to indicate that the shale is later in age than the intrusives and, therefore, later than the sediments into which they were intruded. Further evidence as to this is found in the Knoxville fossils found in the shale, and the fact that, through pet- rographical resemblances, the chert and sandstone are evi- dently Franciscan in age. The fossils, which, in the Knoxw ville, are found only at the base of the series, are found in this shale at the southern edge, This is added evidence that this southern edge of the shale is the true contact line, and thus the base of the formation. On the north side of the shale, on the contrary, the line is very irregular. In the central part of the map, the shale extends only in a narrow belt, while at the east and west ends it spreads out, and leaves the limits of the map. So far as it was possible to obtain the attitude, it is the same throughout, but in several critical localities it was impossible to make any observations. To the North of the shale belt are sandstone, chert, and greenstone, ocC- cupying the same relations as on the South. The shale, which has been shown to be the latest of the formations, is, therefore, lying between two areas of older rocks. Faulting of some sort is the only explanation of this. The movement may have taken place in one of two ways, either to the South, or to the North. The general re- lations, and the fact of the apparent extension of the shale, in the same attitude, under the North ridge, makes the lat=- ter the more probable. In this case, the movement partook more of the nature of a great landslide, than of a fault as ordinarily conceived. The common evidences of landslide structure would, in any case, have long since been removed by erosion. This view of the relations is strengthened by the fact that the shale shows no evidence of crushing or other disturbance at the surface, as would be the case if it had been faulted, when the soft friable shale would have suffered considerably. Taking this interpretation of the structure, the se- quence of events was as follows: First the sandstone and chert were deposited in the order named. These were then intruded by the greenstone, followed by the serpentine. gg After this the region was folded and raised into the zone of erosion. This folding would bring the sandstone and chert together in the manner in which they are now found. After the erosion, the region was again depressed, and the Knoxville shales were laid down on the eroded edges of the older formations. After the deposition of the shale, the region was tilted to the North, inclining the shale at its present attitude. The fault, or slide, which threw the older rocks to the North of the shale, followed. This has been followed since by erosion, making the present topography. As before stated, the relations between the chert and the dark gray sandstone were not accurately determined. It is possible that the chert is older than the sandstone, or that there is more than one horizon of either or both, but in the sections shown, the simpler interpretation has been given. The Ore Deposit. A mineralized zone outcrops as shown on the map. This was not followed on the ground to the limits as shown, but observations made in the course of other work indicate its extent. The zone dips to the North at an angle of about 40°, and lies against a brecciated zone of sandstone, which is apparently due to a fault. The material is mostly quartz and siderite, and contains some cinnabar. In general appearance it resembles the rock found at the sulphur springs mentioned above, and, for this reason, it is concluded that there is a genetic relation between the springs and the ore deposit. Lack of time prevented detailed study of the deposit, and of the ore itself, but thin sections and hand specimens have been prepared for presentation with this paper. The deposit was exploited about twenty-five years ago, but since that time has been hampered by litigation, so that nothing whatever has been done. A tunnel, comprising about two hundred feet of workings remains, located as shown on the map. There is also a lower tunnel, which has since been caved, but which is said to have included five hundred feet of workings. There are a number of prospect shafts and open cuts on the ridge, most of which are now filled with water and debris. For the reduction of the ore a furnace was constructed in the canyon below the lower tunnel. This is now in ruins, as shown by the accompanying photographs. There is a good sized dump below the furnace, showing that a considerable quantity of ore had been worked. ws wm ww () on vo a» Hand specimens are submitted with this paper showing the dark gray sandstone, both fresh and altered; chert, fresh, and in its several degrees of alteration; shale, limestone, and yellowish brown sandstone; serpentine; and greenstone. These have not been explicitly referred to in the text, but are fully labeled. Thin sections are submitted as follows:- 2, 12, 13, 17, 23, 21, :33, 18, 18, 26, 20, 33, 41, 19, 37, 32, 3S, 4, 6, 16, 39, Dark gray sandstone. Dark gray sandstone, weathered. Unaltered red chert. Altered chert. Shale. Yellowish brown sandstone. Greenstone. Serpentine. Igneous rock; not examined for lack of time; location shown on map. Brecciated material from tunnel. Ore. (Twenty-five slides in all.) The localities from which the samples were taken are indicated on the map by a cross and the corresponding num- ber. Strikes and dips are as follows:- Strike Dip 70 23 22 34 38 28 28 63 18 34 70 27 5 =H HH #5 =3 =| HH 57 30 42 40 60 30 78 62 32 16 2 32 4 15 12 60 66 53 69 85 5 = = = = =| +H = = = 37 60 54 50 50 50 70 40 88 34 72 45 v 32 N N N N N N N N N N N N N N N N N N N N E N N N N 2 = =H ® = = = =H 34 Strike N 50 W N 50 Ww E-W -— NN (2) The places where the above were taken are marked on the map by a circle and the corresponding number. (?) indicates that the exact angle is doubtful. -- N (2?) The places where the above were taken are marked on the map by a circle and the corresponding number. (?) indicates that the exact angle is doubtful. € | ed | e | oo Ths map pol with Kedare 4 Stokes BS. Athecss of Moy, 19) 5 7! ook SRY SH To sb) SPPIOX. HER COVEreS » losin , ow AT Zz hb : DEPARTMENT OF THE INTERIOR “=, GF OT.OCTCAT JE oo & CALIFORNIA } MT. DIABLO QUADRANGLE (“Xf 3 A % 121°45 77 38°00 { ne (Concord) renwal d pamEey | ETT EAT ETT RECT ET 5 Ne U.Goode. G . Fin charde J.Goode, Geographer in c arge. riangulation by U.S.Coast and Geodetic Survey. sw IC Flaten oy L. Edition of April 1898, reprinted 1941 in 18 ) 1 2 o 1 Polyconic projection. To place on North American datum urveyed in | i — _ . r . ~ | Co ~ irveyed ir Eee eee p= move projection lines 630 feet south and 320 feet west . . as shown by dotted projection corners. Contour interval 50 feet. Y Pe Datum is mean sea level. MT DIABLO, C4 The United States Geological Survey is making a series of y ys *. [his work has been in progress since 1882, and the published maps standard topographic maps to cover the United States. cover more than 47 percent of the country, exclusive of outlying Possessions. The maps are published on sheets that measure about 161 by 20 inches. Under the general plan adopted the country is divided into quadrangles bounded by parallels of latitude and meridians of longitude. These quadrangles are mapped on different scales, the scale selected for each map being that which is best adapted to general use in the development of the country, and consequently, though the standard maps are of nearly uni- form size, the areas that they represent are of different sizes. On the lower margin of each map are printed graphic scales showing distances in feet, meters, miles, and kilometers. In addition, the scale of the map is shown by a fraction expressing a fixed ratio between linear measurements on the map and eor- responding distances on the ground. For example, the scale swe means that 1 unit on the map (such as 1 inch, 1 foot, or 1 meter) represents 62,500 of the same units on the earth’s surface. Although some areas are surveyed and some maps are com- piled and published on special scales for special purposes, the standard topographic surveys and the resulting maps have for many years been of three types, differentiated as follows: 1. Surveys of areas in which there are problems of great public importance—relating, for example, to mineral develop- ment, irrigation, or reclamation of swamp areas—are made with sufficient detail to be used in the publication of maps on a sss (1 inch = 2,000 feet), with a contour interval of 1 to 100 feet, according to the relief scale of 2 (1 inch = one-half mile) or 31,680 of the particular area mapped. 2. Surveys of areas in which there are problems of average public importance, such as most of the basin of the Mississippi and its tributaries, are made with sufficient detail to be used in the publication of maps on a scale of gi (1 inch=:nearly 1 mile), with a contour interval of 10 to 100 feet. 3. Surveys of areas in which the problems are of minor public importance, such as much of the mountain or desert region of Arizona or New Mexico, and the high mountain area of the northwest, are made with sufficient detail to be used in the publication of maps on a scale of } (1 inch=nearly 2 miles) or zs (1 inch =nearly 4 miles), with a contour interval of 20 to 250 feet. The aerial camera is now being used in mapping. From the information recorded on the photographs, planimetric maps, which show only drainage and culture, have been made for some areas in the United States. Dy the use of stereoscopic plotting apparatus, aerial photographs are utilized also in the making of y THE TOPOGRAPHIC MAPS OF THE UNITED STATES A survey.of Puerto Rico 18 now in progress. The scale of the published maps iS z0- The features shown on toppgraphic maps may be arranged in three groups—(1) water, in¢luding seas, lakes, rivers, canals, swamps, and other bodies of water; (2) relief, including mountains, hills, valleys, and other features of the land surface; (3) culture (works of man), such as towns, cities, roads, rail- The symbols used to represent these features are shown and explained below. roads, and boundaries, Variations appear on some earlier maps, and additional features are represented on some special maps. All the water features are represented in blue, the smaller streams and canals by single blue lines and the larger streams by double lines. The larger streams, lakes, and the sea are accentuated by blue water lining or blue tint. Intermittent streams—those whose beds are dry for a large part of the year— are shown by lines of blue dots and dashes. Relief is shown by contour lines in brown, which on a few maps are supplemented by shading showing the effect of light thrown from the northwest across the area represented, for the purpose of giving the appearance of relief and thus aiding in the interpretation of the contour lines. A contour line repre- sents an imaginary line on the ground (a contour) every part of which is at the same altitude above sea level. Such a line could be drawn at any altitude, but in practice only the con- tours at certain regular intervals of altitude are shown. The datum or zero of altitude of the Geological Survey maps is mean sea level. The 20-foot contour would be the shore line if the sea should rise 20 feet above mean sea level. Contour lines show the shape of the hills, mountains, and valleys, as well as their altitude. Successive contour lines that are far apart on the map indicate a gentle slope, lines that are close together indicate a steep slope, and lines that run together indicate a cliff. The manner in which contour lines express altitude, form, and grade is shown in the figure below. ss > at od 7 NY TEP IN Kuan = ing spurs separated by ravines. The spurs are truncated at The hill at the left terminates abruptly at the valley in a steep scarp, from which it slopes their lower ends by a sea cliff. gradually away and forms an inclined tableland that is trav- ersed by a few shallow gullies. On the map each of these features is represented, directly beneath its position in the sketch, by contour lines. The contour interval, or the vertical distance in feet between one contour and the next, is stated at the bottom of each map. This interval differs according to the topography of the area mapped: in a flat country it may be as small as 1 foot; in a mountainous region it may be as great as 250 feet. In order that the contours may be read more easily certain contour lines, every fourth or fifth, are made heavier than the others and are accompanied by figures showing altitude. The heights of many points—such as road intersections, summits, surfaces of lakes, and benchmarks—are also given on the map in figures, which show altitudes to the nearest foot only. for the altitudes of benchmarks are given in the Geological Sur- More precise figures vey’s bulletins on spirit leveling. The geodetic coordinates of triangulation and transit-traverse stations are also published in bulletins. Lettering and the works of man are shown in black. Bound- aries, such as those of a State, county, city, land grant, town- ship, or reservation, are shown by continuous or broken lines of different kinds and weights. Public roads suitable for motor travel the greater part of the year are shown by solid double lines; poor public roads and private roads by dashed double lines; trails by dashed single lines. Additional public road classification if available is shown by red overprint. Each quadrangle is designated by the name of a city, town, or prominent natural feature within it, and on the margins of the map are printed the names of adjoining quadrangles of which maps have been published. More than 4,100 quad- angles in the United States have been surveyed, and maps of them similar to the one on the other side of this sheet have been published. Geologic maps of some of the areas shown on the topographic maps have been published in the form of folios. Each folio includes maps showing the topography, geology, underground structure, and mineral deposits of the area mapped, and several pages of descriptive text. The text explains the maps and describes the topographic and geologic features of the country and its mineral products. Two hundred twenty-five folios have been published. Index maps of each State and of Alaska and Hawaii showing the areas covered by topographic maps and geologic folios pub- 8 lished by the United States Geological Survey nmiay be obtained the regular topographic maps, which show relief as well as ¥ 7 free. Copies of the standard topographic maps may be obtained drainage and culture. 3 for 10 cents each; some special maps are sold at different prices. A topographic survey of Alaska has been in progress since i ] : A discount of 40 percent is allowed on an order amounting to 1898, and nearly 44 percent of its area has now been mapped. b La $5 or more at the retail price. The discount is allowed on an About 15 percent of the Territory has been covered by maps on a scale of x For most of the remainder of the area surveyed the maps published are on a ( inch = nearly 8 miles). scale of =. sm (1 inch=nearly 4 miles). For some areas of par- ticular economic importance, covering about 4,300 square miles, the maps published are on a scale of 53; (1 inch=nearly 1 mile) or larger. In addition to the area covered by topographic maps, about 11,300 square miles of southeastern Alaska has been 1 0000+ L_ and covered by planimetric maps on scales of The Hawaiian Islands have been surveyed, and the resulting 1 62,500 * > maps are published on a scale of The sketch represents a river valley that lies between two hills. In the foreground is the sea, with a bay that is partly enclosed by a hooked sand bar. On each side of the valley is a terrace into which small streams have cut narrow gullies. The hill on the right has a rounded summit and gently slop- STANDARD SYMBOLS CULTURE (printed in black) order for maps alone, either of one kind or in any assortment, or for maps together with geologic folios. The-geologic folios are sold for 25 cents or more each, the price depending on the size of the folio. A circular describing the folios will be sent on request. Applications for maps or folios should be accompanied by cash, draft, or money order (not postage stamps) and should be addressed to THE DIRECTOR, United States Geological Survey, November 1937. Washington, D. C. 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Mine dumps Tailings or Sand and Intermittent Glacier Spring Well Marsh Su Resid - 2 teied flo " 2g a G3 - > { Or: shown. by contours marsh rr mining debris sand dunes lake Shawn By. conic WOODS {when shown, printed in green) MAP OF A PORTION OF DIABLO MT L____| Slide Material eS S 0 = id tT ¢ S nN © = S$ 2 F nn oo Fea rr HL gk Mag. Ddcy 18°C #2" Mineralized Zone 5 Serpentine 1 tiie . Radiolarian Chert fia Fe ete apts Greenstone dh fy > + 9 yn "3 Se Po cs - co » vw © - 3 Ba of i NYS y NON N// . [= | Dark gray S.5. '1]3' 11415] . = - 112 | = 9 8 ! TN mm x Tia . NT me——— cs ~ he i, SE IRN ~~ -_ EE ——— - i Se by ig WN TN ba . Elev. 500' El ev. 900 Elev 550 Elev 540 Scale ~ 1"= 400’. Elev T00' END OF TITLE