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This institution reserves the right to refuse to accept a copying order if, in its judgment, fulfillment of the order would involve violation of copyright law. GEOLOGY OF THE SIERRA NEVADA By Paul C. Bateman and Clyde Wahrhaftig * U.S. Geological Survey, Menlo Park, California; U.S.G.S. AND University of California, Berkeley The Sierra Nevada is a strongly asymmetric moun- tending south from the Cascade Range. A blanket of tain range with a long gentle \\estern slope and a high volcanic material caps large areas in the north part of and steep eastern escarpment. It is 50 to 80 miles wide, the range. and it runs west of north through eastern California Most of the south half of the Sierra Nevada and the for more than 400 miles—from the Mojave Desert on eastern part of the north half are composed of plutonic the south to the Cascade Range and the Modoc Plateau (chiefly granitic) rocks of Mesozoic age. These rocks on the north (pi. 1). Mount Whitney, in the south- constitute the Sierra Nevada batholith, which is part eastern part of the range, attains a height of 14,495 of a more or less continuous belt of plutonic rocks that feet and is the highest point in the conterminous extends from Baja California northward through the United States. The "High Sierra," a spectacular span Peninsular Ranges and the Mojave Desert, through the of the crestal region, which extends north from Mount Sierra Nevada at an acute angle to the long axis of the Whitney for about a hundred miles, is a glaciated range, and into western Nevada; it may continue at region characterized by numerous lakes and a proces- depth beneath the volcanic rocks of the Snake River sion of 13,000- and 14,000-foot peaks. Plains and connect with the Idaho batholith. The range is a tremendous physical barrier to the In the north half of the range the batholith is flanked passage of moisture eastward from the Pacific. Polar on the west by the western metamorphic belt, a ter- front cyclones expand adiabatically as the\' pass over rane of strongly deformed and metamorphosed sedi- the Sierra Nevada during the winter and cool well mentary and volcanic rocks of Paleozoic and Mesozoic below their dewpoint. Most of the moisture that was age. The famed iVIother Lode passes through the heart obtained during the passage of warm air masses across of this belt. Farther south, scattered remnants of meta- the Pacific is precipitated as snow, which is preserved morphic rock are found within the batholith, espe- as a heavy snow pack at high altitudes and in the shade cially in the western foothills and along the crest in of the forests at lower elevations until late spring or the east-central Sierra Nevada. The batholith extends summer. On the east side of the Sierra Nevada the de- eastward to the east edge of the range, but in the south scending air is warmed adiabatically and can hold more half of the range one can look eastward across Owens moisture than it contains. Hence the arid valleys of Valley to the wall rocks on the east side of the bath- the Great Basin are "lands of little rain." olith making up the White and Inyo Mountains. overlap- But the Sierra Nevada is more than a physical and The story of the Sierra Nevada is in four climatic barrier; until recently it has been a remark- ping parts: (1) a long period in the Paleozoic when ably effective barrier to geologic thought. Its tower- the area was mosth- under the sea receiving sediments; ing eastern escarpment has been a boundary for think- (2) a shorter period during the Mesozoic when the ing about problems in the Great Basin; and geologists Paleozoic strata were downwarped into a gigantic working in the Great Valley, the Coast Ranges, or complexly faulted synclinorium which was filled with even along the west slope of the Sierra Nevada itself, contemporaneous volcanic and sedimentary detritus, have seldom looked eastward for correlations. Even strongly deformed, intruded repeatedly by granitic now, we are only on the threshold of understanding masses, and eroded to a depth of 9 to 17 miles; (3) a the tremendous role the Sierra Nevada has played in period of relative stability in the early Cenozoic; and the geologic history of the West. (4) a period of uplift, tilting, and faulting, preceded and accompanied by volcanic activity, in the late GENERAL GEOLOGIC RELATIONS Cenozoic. MILESTONES OF GEOLOGIC STUDY The Sierra Nevada is a huge block of the earth's crust that has broken free on the east along the Sierra The early literature of the Sierra Nevada is replete Nevada fault system and been tilted westward. It is with the names of geologic "greats" who were lured overlapped on the west by sedimentary rocks of the into attacking some of its vexing problems—names King, Great Valley and on the north by volcanic sheets ex- such as John Muir, J. D. Whitney, Clarence Lawson, Adolph * Publication authorized by the Director, U.S. Geological Survey. Bateman Joseph Le Conte, A. C. "Andy" prepared the parts of the report that deal with the bedrock geology Lindgren, F. L. Ransome, W. H. and Wahrhaftig the parts that deal with the Cenozoic geology. Knopf, Waldemar [ 107] 108 Geology of Northkrn California Bull. 190 Turner, and Francois Mattlics. The first geologic rately shows the separate granitic intrusive rocks in studies were begun a little more than a hundred years the \'oscmitc region, and his brief accompanying text ago by the CJeological Survey of California, headed includes descriptions of field relations that establish geologists the sequence of intrusion. This map served as the base by J. D. Whitney. In the Sierra Nevada, of the "\Vhitnc\- Survc>'" devoted their attentions for F.rnst Cloos' (1936) well-known stud>' of the pri- chicfl\- to the "gold belt" of the metamorphic western mar\- structures of the granitic rocks, "Der Sierra foothills and to reconnaissance of the still largely un- Nevada pluton," and also provided a test for age de- known higher granitic countr\- to the east and south- terminations of rocks by the potassiuni-argf)n (K-.-\r) east (Whitney, 1865). In 1886 Waldemar Lindgren method (Curtis and others, 1958). and H. W. Turner, under the direction of G. F. In 1934 K. B. Ma\() published tiie results of studies Becker, were assigned by the U.S. Geological Survey in the Laurel and Convict Basins of the eastern Sierra to stud_\- the "gold belt," and between 1894 and 1900 Nevada, and in 1937, 1941, and 1947 he published the Lindgren and Turner, together with F. L. Ransome results of reconnaissance structural studies of the gra- \\ho had joined them later, published 12 regular folios nitic rocks of the eastern Sierra Nevada. and I special folio, which together are known as the Ju.st before World War II, Durrell (1940) and "gold belt" folios (Lindgren, Turner, and Ransome, Macdonald (1941) published reports that deal with 1894-1900). In terms of the time expended in field- sizeable areas in the western foothills south of the work and report preparation measured against mag- w estern metamorphic belt. These authors were con- nitude and value, these folios are truly a remarkable cerned primariK' with the structure and metamor- achievement. The\' were followed, in 1911, by Lind- phism of the metamorphic rocks, but also made an gren's report, "The Tertiary gravels of the Sierra effort to distinguish the different granitic rocks. About Nevada." In 1915 Adolph Knopf undertook a study the same time. Miller and Webb (1940) published a of the Mother Lode System (Knopf, 1929); in 1932 map and description of the Kernville 30-minute quad- H. G. Ferguson and R. W. Gannet published on the rangle in the southern part of the Sierra Nevada. gold quartz veins of the Alleghany district; and in Somewhat later Ross ( 1958) published a report on the 1940 W. D. Johnston published the results of a stud> bedrock geology of a part of Sequoia National Park, of the Grass Valley gold district. and Hamilton (1956a, 1956b) published the results of These publications provided much information on studies in the Huntington Lake area of the central the character and distribution of the rocks in the west- Sierra Nevada. ern metamorphic belt, but the extremely comple.x During World War II, geologists of the U.S. Geo- ob- stratigraphy and structure of the belt remained logical Survey investigated the tungsten deposits of the Taliaferro progress in un- scure. N. L. made some Sierra Nevada, and at the end of the war undertook raveling the structure and stratigraphy, chiefly by regional studies of some of the more productive areas applying criteria indicating the top directions of beds in the central Sierra Nevada.