During the past few years, the writers have been studying the stratigraphy and structural geology of the Tonopah and Hawthorne quadrangles, in western Nevada. An unusually complete section of Triassic and Lower Jurassic rocks merits brief preliminary description prior to the publication of more complete papers, now in preparation, dealing with the stratigraphy and structure of the region. The field work has been carried on at various times under the auspices of the United States Geological Survey, the Geological Department of Stanford University, and the Geological Society of America. The writers gratefully acknowledge much assistance received from Dr. T. W. Stanton.
The study has covered an area of about 7,700 square miles, lying in parts of Mineral, Esmeralda, and Nye counties, Nevada. Much of the area is covered with Tertiary sediments and lavas, and there are large bodies of granitic intrusives, satellites of the Sierra Nevada batholith. Paleozoic rocks, . . .