Biostratigraphic and paleogeographic utility of Cambrian-Ordovician trilobite faunas in Alaska

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Biostratigraphic and paleogeographic utility of Cambrian-Ordoviciantrilobite faunas in Alaskaby John Taylor, Indiana University of PennsylvaniaEAR-1325333ABSTRACTPaleogeographic maps of North America, which depict our continent as it appeared at certain times in Earth history, are utilized by geologists exploring for fossil fuels and other critical societal resources, climate specialists seeking greater insight to conditions that prevailed on our planet in 'deep time', and geoscientists investigating the behavior of tectonic plates and derivative processes that shape the surface of our planet. But the data for constructing such maps for the Cambrian and Ordovician Periods, a time of greenhouse climate, are exceedingly sparse for the northern half of the continent, and the Arctic regions in general. This project will improve that situation through detailed study of Cambrian-Ordovician trilobite (extinct marine arthropod) faunas)from the Arctic Alaska Terrane (AAT) of northern Alaska, and the Yukon Stable Block (YSB) of eastern Alaska. It will utilize large fossil collections archived by geologists of the U.S. and Canadian Geological Surveys over the past century, supplemented by new material collected in several key areas in Alaska. The goal for the AAT is to test, by comparing newly discovered faunas from its North Slope Subterrane (NST) with trilobites previously reported from the Seward Terrane (ST) in western Alaska, the hypothesis that the thick limestone succession in the NST was deposited somewhere in northeastern (modern coordinates) North America, whereas the ST originated in or near Siberia. In the YSB, thorough documentation of rocks and fossils in the Jones Ridge Limestone will refine correlation with rocks of the same age in other regions. For many of the horizons targeted for study, the data from Jones Ridge will be the first information acquired from the entire northern half of the continent. The refined time control through this thick (ca. 450m) stack of limestone preserved near the northwestern corner of North America will serve to test the claim of continent wide (and perhaps global) extent for numerous events documented across broad areas in the U.S. and southern Canada, on the opposite side of the continent. These include (among others), 1) a number of significant rises and falls in sea level and 2) episodes of platform-wide suppression of microbial reef development in the aftermath stage boundary extinctions in the late Cambrian. The scientific results of the proposed project will benefit society by advancing knowledge of the Arctic region, an area rich in vital resources but still a frontier with respect to our understanding of even basic aspects of its tectonic history. Extensive involvement of undergraduate Geology majors and Earth and Space Science Education majors as junior collaborators in the project will produce a cadre of professional geoscientists with exceptional insight and secondary school teachers able to teach science with the enthusiasm and knowledge of someone who has actually done science.