Title: Preliminary surficial geologic map of selected parts of Clayton Valley and the northwest Montezuma Range piedmont, Esmeralda County, Nevada
Authors: T. Andrew Foy, Kurt L. Frankel, and Zachery M. Lifton
Series: Open-File Report 16-2
Format: plate: 27.5 x 29 inches, color; text: 3 pages, b/w
Mapping efforts were focused in the southeastern portion of Clayton Valley, where the surface trace of the Clayton Valley fault is best expressed in the late Quaternary stratigraphy. Mapping was conducted using 1-m-resolution color orthorectified aerial photographs from the U.S. Department of Agriculture as a base map and aided by aerial stereo photographs provided by the Bureau of Land Management. Alluvial fans were divided on the basis of well-established criteria, such as height above the active channel, development of desert varnish and pavement, degree of rubification, soil development, degree of fan dissection, and bar and swale surface morphology (e.g., Bull, 1991; Ritter et al., 1993; Frankel and Dolan, 2007). Eight alluvial fan units were mapped, each of which are consistent with the western North American alluvial stratigraphic framework established by Bull (1968, 1991). From oldest to youngest, the fan units are as follows: Q2a, Q2b, Q2c, Q2d, Q3a, Q3b, Q3c, and Q4. Surfaces of Q3b age are further subdivided into separate map units due to the fact that the southern portion of the map area contains extensive Q3b deposits with cryptobiotic soil on the fan surface. Undivided bedrock and volcanic ash units were mapped through portions of the valley, some of which also appear to have been deformed by earlier Cenozoic faults. However, the main focus of mapping efforts herein was the Quaternary alluvium and associated faults, and thus the bedrock units have not been divided.
In addition, some of the displaced fan units were dated using terrestrial cosmogenic nuclide (TCN) 10Be depth profiles to determine a surface exposure age of the unit. Details of the TCN dating can be found in Foy (2011) and Foy et al. (2012).
This map was prepared with support from the National Science Foundation, Geological Society of America, Sigma Xi, and the White Mountain Research Station.
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