Glaciation in the Great Basin of the Western United States
Quaternary Science Reviews 20 (2001) 1377}1410 Glaciation in the Great Basin of the Western United States Gerald Osborn *, Ken Bevis Department of Geology and Geophysics, University of Calgary, Calgary, Alberta, T2N 1N4, Canada Department of Natural Sciences, Western Oregon State University, Monmouth, OR 97360, USA Abstract Forty individually named ranges, plateaus, and massifs draining wholly or partly into the Great Basin of the western United States show de"nite evidence of Pleistocene glaciation. The most obvious deposits are a family of moraines designated, among other names, `Tiogaa, `Angel Lakea, and `Pinedalea. Such moraines generally can be traced from range to range away from described type moraines. These deposits have been numerically assigned to Late Wisconsinan glaciation in the Wasatch Range, White Mountains, Boulder Mountain, and Sierra Nevada on the basis of radiocarbon and surface-exposure ages, and have been assigned to Late Wisconsinan time in several other ranges on the basis of relative-age studies. The type Angel Lake moraine, and most other equivalent moraines across the Great Basin, are thick, hummocky, lobate piles of till rather than looping ridges. The thicknesses of the moraines (often 60#m) can be explained by heavy debris loads, and/or glacial advance, retreat, and readvance to the same positions a number of times, which is consistent with recent evidence that multiple Late Wisconsinan advances, possibly related to Heinrich and Dansgaard-Oeschger events, occurred in the Sierra Nevada. Pre-Angel Lake deposits occur in many Great Basin ranges, but it is currently di$cult or perhaps impossible to determine if these deposits are equivalent to each other and what their relationship is to pre-Tioga deposits in the Sierra Nevada.
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