| Paper No. 163-9 | ||
| Presentation Time: 3:30 PM-3:45 PM | ||
| WEATHERING, PROVENANCE, AND TECTONIC SETTING OF THE NEOPROTEROZOIC STIRLING QUARTZITE, DEATH VALLEY AREA, CALIFORNIA: A GEOCHEMICAL PERSPECTIVE | ||
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SCHOENBORN, William A. and FEDO, Christopher M., Earth & Environmental Sciences, The George Washington Univ, 2029 G St. NW, Washington, DC 20052, schoenborn.william@epa.gov The Neoproterozoic to Cambrian age stratigraphic succession along the Cordilleran margin in eastern California preserves a stratigraphic record that passes through several significant stages, including initial fault-controlled rift-basin development followed by subsequent thermal-mechanical and loading subsidence of a passive margin. Major-, trace-, and rare-earth-element (REE) geochemistry of the Stirling Quartzite are used to evaluate the nature of provenance in an effort to reconstruct the tectonic setting of sediment formation. In A-CN-K compositional space Stirling sediments define a linear array that suggests the unweathered source has a granodioritic composition. Such scatter indicates that fluvial systems incised most parts of a well developed weathering profile. Chondrite-normalized REE patterns are of uniform shape with a negative Eu anomaly (Eu/Eu* = 0.66), LREE enrichment (chondrite normalized La/Sm=4.17), and a flat heavy REE distributions (chondrite normalized Gd/Yb=1.69) that are characteristic of average upper crust, average shale, and bedrocks of the Mojave region. A plot of Th/Sc vs. Zr/Sc suggests that Stirling sediments experienced zircon enrichment due to sedimentary sorting and recycling, a result suggestive of passive margin sedimentation. Variation in CIA vs. stratigraphic position shows an upward excursion from intensely weathered towards toward less weathered values (CIA: 74 to 53, PIA: 98 to 78) from the lower to middle Stirling Quartzite. In the absence of a tectonic event to drive such changes, such compositional variation is likely to result from variations in weathering. | ||
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2002 Denver Annual Meeting (October 27-30, 2002)
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| Session No. 163 Precambrian Geology Colorado Convention Center: C101/103 1:30 PM-3:45 PM, Tuesday, October 29, 2002 | ||
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