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43505-B8
Alluvial Facies Architecture and the Role of Climate and Tectonics in Basin-Fan Systems, Death Valley, California
Jeffrey R. Knott, California State University (Fullerton)
The substantial tasks completed during 2007-08 that were supported by ACS-PRF grant 43505-B8 are:
a) Completion of an undergraduate independent study project,
b) 40Ar/39Ar dating of Death Valley lake deposits
c) Radiocarbon dating of Harper Lake
d) Radiocarbon and paleomagnetic dating of Searles Lake deposits
During 2007-08, I and undergraduate student Steven Okubo mapped the geology of the Kit Fox Hills with the support of this grant. Mapping was done at a scale of 1:12000 and was the first detailed map (previous map was 1:62500) of the area. This work was an independent research project for Steve and extended previous work completed by other undergraduate students. Tephra samples collected as part of the project were prepared (sieved, magnetically separated, heavy-liquid separated and acid washed) by Steve and submitted to the U.S. Geological Survey laboratory for analysis. We also collected two samples for 40Ar/39Ar and submitted those samples to the Berkeley Geochronology Laboratory. We have obtained ages that show that the Kit Fox Hills represents a 3.5-0.5 Ma stratigraphic section and will allow interpreting climatic versus tectonic forcing of alluvial fan. Mapping of faults was presented at the 2008 Cordilleran Section meeting by an undergraduate student (Brenden Taylor).
In working out the Death Valley stratigraphy and younger climatic record, I have collected samples to compare the climatic record in two adjoining river systems. In the Owens River system, samples collected from the Pleistocene lake deposits of the Wilson Creek Formation have been prepared and will be analyzed in October, 2008. These analyses were delayed as the initial student who was to perform the research decided to pursue other options. I have also obtained radiocarbon and paleomagnetic chronology from Searles Lake. These data were presented at the Spring 2008 AGU meeting and additional data will be presented at the Fall 2008 AGU meeting. I have also worked with a student on the chronology of Harper Lake along the ancient Mojave River system. These data indicate that Harper Lake is 29-43 ka and relatively short lived. Data from these lake systems are compared to alluvial fan chronology in Death Valley to correlate wet, lake-forming periods with dry, fan-forming periods. The Harper Lake data were presented by a graduate student (Anna Garcia) at the 2008 Cordilleran Section meeting.
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