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The Pershing olistostrome: Evidence for the Triassic shelf-basin transition in the western Great Basin

By
Frederick R. Heck
Frederick R. Heck
Department of Physical Sciences, Ferris State University, Big Rapids, Michigan 49307 USA,
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Published:
January 01, 2000

Abstract

The Pershing district of the southern Humboldt Range, northwestern Nevada, contains a large, Upper Triassic submarine olistostrome containing carbonate clasts from pebble size to 700 m in length that are supported mostly my lime-mud matrix. The olistostrome comprises debris flows separated by intervals of hemipelagic sedimentation, turbidity flows, and density modified grain flows. The olistostrome body is triangular-prism shaped with a flat top and keel-like base. It lies in a thick sequence of fine-grained siliciclastic rocks. The lower submarine gravity flows were deposited in a preexisting trough at a lower slope or base-of-slope position. The highest gravity flow filled the trough and spilled over its sides. The source of the olistostrome clasts and matrix was a carbonate platform (Dun Glen Formation) to the northeast that formed on the surface of a preexisting shallow-marine delta. The olistostrome and older shelf-basin transitional rocks of the Humboldt Range indicate the existence of a Middle and Upper Triassic shelf-basin transition with an arcuate trace that is convex to the southwest at the southern Humboldt Range.

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GSA Field Guide

Great Basin and Sierra Nevada

David R. Lageson
David R. Lageson
Department of Earth Sciences Montana State University Bozeman, MT 59717 USA
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Stephen G. Peters
Stephen G. Peters
Reno Field Office Mackay School of Mines, MS-176 University of Nevada Reno, Nevada 89557-0047 USA
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Mary M. Lahren
Mary M. Lahren
Department of Geological Sciences MS-l72 University of Nevada Reno, Nevada 89557 USA 2000
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Geological Society of America
Volume
2
ISBN electronic:
9780813756028
Publication date:
January 01, 2000

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