Railroad Valley is situated near the center of the eastern half of the Great Basin where more than 20,000 feet of limestone, sandstone, and shale were deposited in a Paleozoic miogeosyncline. During Mesozoic time the region was uplifted and served as a barrier between basins on the east and west. Fresh-water sediments and volcanic rocks may have been deposited, however, for Cretaceous beds of this kind have been identified a short distance northwest. In Tertiary time the basin-and-range structure now found in the Great Basin began to form. Sediments were deposited in the basins by lakes, streams, landslides, and other agencies, and volcanic material was widely distributed in the basins and on the ranges. Oil production at the Shell Oil Company's Eagle Springs Unit 1 is fr m welded tuff, probably Tertiary in age.

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