Collaborative Research: Integrated Geochronology and Paleomagnetism of Neoarchean-Paleoproterozoic Dikes in Wyoming, A Keystone of North American Cratons

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Supercontinents arise on the Earth when the continents cluster together, typically on one side of the Earth, as a result of multiple tectonic collisions. The past existence of supercontinents is of great interest to the tectonics scientific community, and society in general, for example for the tracing of mineral deposits. The continents today are fragments of the Pangean supercontinent, which existed during the Mesozoic age of the dinosaurs. Several lines of evidence suggest the existence of even earlier supercontinents, the subject of this study. These researchers aim to reconstruct the arrangement of continental pieces between 2.7 and 2.1 billion years ago, to determine whether ancient supercontinent cycles occurred at that time. The research will be carried out in all the major mountain ranges of Wyoming, over two summer field seasons of rock sample collection by the two principal investigators and their graduate and undergraduate students. In addition, the methods and data will be incorporated into scientific outreach programs aimed at ninth-grade inner-city students. Finally, the results will be illustrated in a computer animation made available to the general public as an educational resource. The study focuses on Wyoming, one of the cratons of North America that currently is least well known in terms of its changing positions through the Neoarchean-Paleoproterozoic interval. The researchers will be examining drift histories, conjugate margins, and cratonic chronologies for purposes of supercontinental reconstruction. In many regards, Wyoming is a central keystone in the arrangement of North American cratons during the Neoarchean-Paleoproterozoic eras. The research will entail two complementary methods: geochronology using several well established and precise isotopic methods, and paleomagnetism of rock and mineral samples that contain magnetic domains that are particularly resistant to resetting. The combination of these analyses provides a powerful tracking method for the analysis of supercontinent cycles. These measurements of time and space will be applied to dike rocks from the ancient roots of now-eroded lava plains in Wyoming. The dikes are ideal targets for the close integration of the two research methods, as indicated by preliminary data. Such data have generated much excitement that refined apparent polar wander paths from this study may result in a re-evaluation of Neoarchean-Paleoproterozoic supercontinental assembly.