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

科罗拉多高原中生代地层碎屑锆石年代学：大陆古地理和古构造意义Dickinson，G. E. Gehrels，P.G. Decelles（University of Arizona）1987 - 0341987摘要通过测定锆石中铀和铅的同位素比率，获得锆石矿物中单个砂粒的放射性年龄的能力，现在使得确定侵蚀基岩来源的年龄成为可能，这些侵蚀基岩来源为沉积地层提供了砂粒。通过首次将这种技术系统地应用于科罗拉多高原的地层，该高原暴露了北美最完整的中生代序列，我们期望将我们对该大陆中生代古地理的理解提高到以前无法达到的水平。通过将北美不同地区潜在基岩源的年龄知识与科罗拉多高原地层中锆石颗粒年龄的新信息相结合，我们可以推断出中生代古河流的模式，这些河流将沙子运送到古代大陆表面，以及古风系统，这些系统负责全球地质记录中最大的古沙丘场的沉积。了解中生代时期横贯大陆的沉积物输送方向，将有助于了解大陆边缘阿巴拉契亚山脉（东部）和科迪勒纳山脉（西部）的演变，因为古水系的源头是高地，随着高地因构造活动而隆起或因侵蚀而减弱，其形态也会发生变化。该项目的设计涉及参与研究的所有阶段的本科生作为教师调查的初级同事。

Detrital Zircon Geochronology of Colorado Plateau Mesozoic Strata: Implications for Continental Paleogeography and PaleotectonicsW.R. Dickinson, G.E. Gehrels, P.G. Decelles (University of Arizona)EAR-0341987ABSTRACTThe 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.