Detrital Zircon Geochronology of Colorado Plateau Mesozoic Strata: Implications for Continental Paleogeography and Paleotectonics

University Of Arizona, Tucson AZ

Investigators

Abstract

Detrital Zircon Geochronology of Colorado Plateau Mesozoic Strata: Implications for Continental Paleogeography and Paleotectonics W.R. Dickinson, G.E. Gehrels, P.G. Decelles (University of Arizona) EAR-0341987 ABSTRACT The ability to obtain radiometric ages for individual sand grains of the mineral zircon by determining isotopic ratios of uranium and lead contained within the zircon now makes it possible to establish the ages of the eroded bedrock sources that contributed sand grains to sedimentary strata. By applying this technique systematically for the first time to strata of the Colorado Plateau, which exposes the most complete Mesozoic succession in North America, we expect to advance our understanding of the Mesozoic paleogeography of the continent to a level not previously attainable. By coupling knowledge of the ages of potential bedrock sources in different parts of North America with the new information on the ages of zircon grains in strata of the Colorado Plateau, we can infer the patterns of Mesozoic paleorivers that transported sand across the ancient continental surface, and of paleowind systems responsible for deposition of vast paleodune fields that are among the largest in the global geologic record. Knowing the directions of transcontinental sediment transport through Mesozoic time will shed light in turn on evolution of the Appalachian (eastern) and Cordilleran (western) mountain chains of the continental margins because paleodrainages head in highlands, and change configuration as highlands are uplifted by tectonic activity or subdued by erosion. The design of the project involves participation by undergraduate students in all phases of the research as junior colleagues of the faculty investigators.