28 Geologic Mapping in the West (Posters)
This poster session highlights geologic mapping in the western Cordillera and Rocky Mountains. We encourage submissions that explore bedrock and surficial geology, geophysics, hydrology, hazards, and more. Both professional and student submissions are welcome.
Tuesday, 19 May 2026
8:00 AM - 5:30 PM
Alvarado D/E
Field Relationships of Volcanic, Lacustrine and Eolian Map Units at Upsal Hogback, Churchill County, Nevada
Paper number: 28-9
Program: Technical Sessions
Time: 8:15 AM – 8:15 AM
Authors
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James FauldsNevada Bureau of Mines and Geology - University of Nevada Reno, Reno, NV
Abstract
The Nevada Bureau of Mines and Geology is conducting detailed geoframework mapping of the Upsal Hogback 7.5-minute quadrangle in Nevada, supported by funding from the USGS NCGMP Statemap program. The eponymous Upsal Hogback is inferred to represent a Late Pleistocene basaltic Surtsey-style eruption through the waters of Lake Lahontan. The “hogback” is comprised of basaltic tephra and consolidated layers of palagonite tuff with multiple eruptive centers previously identified. The volcanic upland feature is flanked by basin-filling lacustrine beds of Pleistocene Lake Lahontan. A basaltic tephra layer inferred to relate to the eruptive episode at the hogback extends away from the upland and is overlain by a few meters of lacustrine material. A coating of tufa extends across the upland volcanic rocks and the depositional surface of the deep-lake deposits. Subsequent lowstands of Lake Lahontan have produced wave cut benches in both the lacustrine deposits and the volcanic upland as well as on adjacent bedrock highlands, and beach barrier bars on adjacent older alluvial fan deposits. The lowstands resulted in development of a mosaic of playa and eolian sand deposits across the eroded lake surface. A veneer of cinders across the modified lake-sediment surface and across overlaying Holocene dunes are attributable to continued deflation and erosion of the volcanic hogback. Field relationships of these deposits provide a relative chronology that can be related to previously published lake-inundation curves for the region.
Geological Society of America Abstracts with Programs. Vol. 58, No. 4
doi: 10.1130/abs/2026RM-410720
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