--> Abstract: New Tectonics from Higher Resolution Chronostratigraphy: Upper Paleozoic of the Western United States, by Walter S. Snyder, Vladimir I. Davydov, Mark D. Schmitz, James H. Trexler, and Patricia H. Cashman; #90078 (2008)

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New Tectonics from Higher Resolution Chronostratigraphy: Upper Paleozoic of the Western United States

Walter S. Snyder1, Vladimir I. Davydov1, Mark D. Schmitz1, James H. Trexler2, and Patricia H. Cashman2
1Dept. Geosciences, Boise State University, Boise, ID
2Dept. Geological Sciences, University of Nevada, Reno, Reno, NV

Higher resolution biostratigraphy has allowed the identification of multiple episodes of upper Paleozoic tectonism within the western U.S. Along with correlatives in the Canadian cordillera, these new insights are forcing us to rethink the tectonic framework of this continental margin. Physical stratigraphic and structural assessments are documenting the nature of these events, however, because the upper Paleozoic biostratigraphic framework of the western U.S. has not yet been correlated to global standards, and hence to the evolving radiometrically calibrated time scale, there is much room to improve the precision of the timing for these events. Starting with the latest Devonian-Early Mississippian Antler orogeny, eleven distinct tectonic events disrupted the continental margin, each of variable magnitude and spatial extent. The last encompasses the Sonoma orogeny, but the same processes appear to have continued through the Triassic into at least the earliest Jurassic. This tectonism is marked by the initiation and destruction of a succession of sedimentary basins and more localized folds and thrust faults. In some basins, a signature of 400,000 yr Milankovitch cycles can be seen, but in most, this signal is masked by the nature of the sedimentary fill. The structural-tectonic origins of these basins remains difficult to determine - including that of the classic Antler "foreland basin." This analysis is exacerbated by the preliminary assessment that some of the outboard accreted terranes record tectonic events that may correlate with those on the continental margin. Full assessment of the timing and nature of this tectonism and associated basins will remain elusive until we have a better calibrated biostratigraphic framework - and that requires a global perspective.

 

AAPG Search and Discover Article #90078©2008 AAPG Annual Convention, San Antonio, Texas