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The AAPG/Datapages Combined Publications Database
AAPG Bulletin
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Railroad Valley is situated in the western part of a migeosyncline where sediments representing all of the Paleozoic systems accumulated to a thickness of about 22,000 feet. The region was uplifted in late Permian or early Mesozoic time and no marine invasion is known to have occurred since. Great thickness of fresh-water sediments and volcanic rocks were deposited, possibly partly during Cretaceous and early Tertiary, but mostly in Miocene and later time. The faulting which has formed the present-day basin-and-range structure of the region also took place in late Tertiary and Quaternary time.
Wells drilled in Railroad Valley have penetrated several thousand feet of presumed Tertiary beds which can be compared in a general way with rocks exposed on the east side of the valley. Oil-saturated welded tuff in this Tertiary (?) section was encountered at a depth of 6,445-6,880 feet in Shell's Eagle Springs Unit 1 and the well was completed with an initial production of 373 barrels of oil per day from this zone. Shell's Eagle Springs Unit 2, about 9 miles southwest of Unit 1, encountered more than 2,000 feet of similar volcanic material but found only minor oil shows in it. The zone of welded tuff was not encountered in Unit 3, about 5 miles south of Unit 1. All three of these wells penetrated Paleozoic rocks below the Tertiary (?) but found only minor oil shows.
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