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The AAPG/Datapages Combined Publications Database

Utah Geological Association

Abstract


Cenozoic Geology and Geothermal Systems of Southwestern Utah, 1994
Pages 97-103

Review of the Quaternary Geology of the Sevier and Black Rock Deserts

Charles G. Oviatt

Abstract

The Sevier basin, a complex tectonic basin occupied by the Sevier and Black Rock Deserts, contains a thick succession of Tertiary sediments primarily of lacustrine origin. These include Oligocene evaporites and Miocene to Pliocene fine-grained deposits and limestone. A shallow lake or series of lakes apparently existed almost continuously in at least part of the basin from prior to 3 Ma until at least 758 ka. The stratigraphic record for the period from 758 ka to about 150 ka, however, is largely missing from the basin. Basalt flows that range in age from 0.8–1 Ma cap pedestals of fine-grained lake sediments and indicate topographic inversion and erosional removal of a vast quantity of lacustrine sediment from the basin floor caused by lowering of the threshold between the Sevier and Great Salt Lake basins. At Bishop ash time (758 ka) a fresh- to brackish-water lake in the Sevier basin probably overflowed northward to a shallow lake in the Great Salt Lake basin. Deposits of the Little Valley Lake cycle (about 150 ka) are exposed in a small area along the Sevier River near Delta, and during the last major (Bonneville) lake cycle (about 20–12 ka) numerous facies were deposited throughout the basin, including offshore marl, shorezone gravel and sand, and fine-grained deltaic units. Even the Bonneville deposits, however, have been eroded from most of the region. The last Pleistocene lake in the basin was Lake Gunnison (about 11–10 ka), which was followed by much smaller lake expansions in Sevier Lake during the Holocene.


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