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During revision of the 1938 edition of the State Geologic Map, the Division of Mines has examined and compiled available geologic mapping, published, and unpublished. Thirty topographic sheets, by the Army Map Service, are to serve as the base for the revised map. The first group of 8 of these sheets, in southern California, is in press. Geologic mapping which may be considered adequate for the 1:250,000 scale adopted for the new map covers over half (57%) of the state's area; 70% of this has been published. The most completely mapped provinces are the Sierra Nevada and the central and southern Coast Ranges. About 70% of the Sierra Nevada is covered by adequate available maps, and possibly 90% of the central and southern Coast Ranges has been adequately mapped, the latter mainly by petroleum geologists. Only 27% of the Mojave-Colorado desert is adequately mapped.
Geologic mapping in the state is progressing rapidly by the U. S. Geological Survey, the universities, the State Division of Mines, and other geologists. Approximately two-thirds of the geologic mapping in California published since 1940 has been published by the Division of Mines. The Division in September, 1953, had in press 6 quadrangle geologic maps, and field mapping has been completed in 25 additional 15-minute quadrangles. The U. S. Geological Survey, in cooperation with the Division of Mines, has been mapping mineralized areas in the state, and, in addition to the cooperative investigations, is mapping in connection with several mineral commodities, including the salines of the Mojave Desert; this last is to yield a reconnaissance geologic map of the Mojave within two years. T e Survey is also reconnaissance-mapping 15,000 square miles in northwestern California. Several universities are sponsoring mapping projects, including the University of California in the high Sierra Nevada, Sierra Nevada foothills, the Salinas Valley, and Diablo Range; California Institute of Technology in the San Jacinto and Avawatz mountains; University of Southern California in the southern Coast Ranges and Peninsular Ranges; and Stanford University in the east Shasta district, Sierra Nevada foothills, and Santa Lucia and San Bernardino mountains.
The Division of Mines encourages the cooperation of geologists in furnishing information on geologic mapping in progress in the State and welcomes their inquiries.
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