Lake Tecopa and its environs: 2.5 million years of exposed history relevant to climate, groundwater, and erosion issues at the proposed nuclear-waste repository at Yucca Mountain, Nevada
Roger Barron Morrison, Martin D. Mifflin, 2000. "Lake Tecopa and its environs: 2.5 million years of exposed history relevant to climate, groundwater, and erosion issues at the proposed nuclear-waste repository at Yucca Mountain, Nevada", Great Basin and Sierra Nevada, David R. Lageson, Stephen G. Peters, Mary M. Lahren
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This one-day field trip gives an overview of the geologic framework of this region, with emphasis on its Quaternary geomorphologic and hydrogeologic aspects. Its route (Fig. 1) is northwest from Las Vegas, along an arm of Las Vegas Valley, the problematic trace of the Las Vegas shear zone, to where the shear zone disappears into the Tertiary volcanic field of southern Nevada. Enroute, we pass several late Pleistocene/early Holocene groundwater discharge areas that have been long inactive, and visit a typical one. Then we go west to one of many warm springs in Ash Meadows, a major regional groundwater discharge area, noting exposures of 2-3-m.y.-old volcanic-ash beds within a few m of the surface, indicating that the Amargosa Desert basin has been a pediment, not a depocenter, for at least the last 1 m.y.
Thence, we travel south along the Amargosa River to Tecopa Valley, the site of pluvial Lake Tecopa and the chief objective of this trip. Its badlands expose a very detailed record of Quaternary climatic change (many pluvial-interpluvial cycles and consequent erosion and groundwater cycles) and tectonism for the last 2.5 m.y. This record is relevant to climatic, groundwater, erosion, and tectonic issues at the Yucca Mountain, Nevada, proposed nuclear-waste repository. It also has important evidence on the significance of episodes of regional pedimentation versus alluvial-fan aggradation during the Quaternary in the Great Basin. After 8 stops in Tecopa Valley, we return to Las Vegas, briefly viewing more extinct groundwater-discharge areas of late Pleistocene-early Holocene age in Chicago and Pahrump Valleys.
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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.