The Pershing olistostrome: Evidence for the Triassic shelf-basin transition in the western Great Basin
Frederick R. Heck, 2000. "The Pershing olistostrome: Evidence for the Triassic shelf-basin transition in the western Great Basin", Great Basin and Sierra Nevada, David R. Lageson, Stephen G. Peters, Mary M. Lahren
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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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Great Basin and Sierra Nevada, the second volume of the Geological Society of America Field Guide Series, focuses on the dynamic and spectacular geology of this region, providing the inspiring backdrop for the 2000 GSA Annual Meeting in Reno. This volume gives complete coverage of field trips held in conjunction with that meeting, and contains 20 chapters organized into three sections. The first section consists of 16 chapters arranged in geochronological order, beginning with the active tectonics of Lake Tahoe and the historical surface faulting and paleoseismicity of the central Nevada seismic belt, and ending with the Neoproterozoic glacial record of Death Valley. In between are chapters dealing with Basin and Range extension, Eocene magmatism, Mesozoic plutonism in the Sierra Nevada, Paleozoic subduction, and Ordovician stratigraphy, to name a few. The second section covers the geology of the Nevada Test Site and the nuclear-waste repository at Yucca Mountain. The last section is an invited field guide from the 1999 GSA Cordilleran Section meeting that covers the wines and geology of Napa Valley, California. Overall, Great Basin and Sierra Nevada is a comprehensive compilation of new and exciting research on this amazingly diverse region, with well-crafted guides to field localities of special interest. Full-color plates in some chapters make this guide an especially appealing and useful volume.