SGER: Testing Chemostratigraphic Correlation in Terrestrial Sediments: Hell Creek Formation, Northeastern Montana

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AbstractThe survival of many environ- mentally sensitive vertebrate lineages (Archibald and Bryant 1990) belies the hypothesized severity of the K/T boundary event. Testing alternative hypotheses of extinction and survival across the K/T boundary requires a more detailed understanding of environmental change and biotic response preceding the bolide impact. To develop this context, we need an integrated picture of change in the flora, fauna and physical environment in the latest Cretaceous. Such an integration has not yet been possible because fossil floras and faunas are preserved in different depositional environments at different localities within an outcrop belt. To unite these records, a method for detailed correlation among localities is needed.I propose to develop the framework for carbon isotope chemostratigraphic correlation of fossil localities within the Hell Creek Formation (mostly latest Maastrichtian) in northeastern Montana.The proposed work will test the following hypotheses essential to the development of thechemostratigraphic framework:o Secular variation in the carbon isotope signature of land plant organic carbon in the Hell CreekFormation exceeds that expected by random variation and spatially averaged plant vital effects.o Features of the secular carbon isotope curve are recognized at different localities and can act as stratigraphic tie points to correlate within the Hell Creek Formation.I will test the first hypothesis by examining the curve for quantitative variation that exceeds that expected by random variation and plant vital effects (Arens et al.2000).I will then test the second hypothesis by correlating among individual localities, and to the marine record,using features of the reference curve. If successful, this approach could be widely applied in rocks younger than the Devonian, when vascular plants colonized land. It will allow fossil collections from various localities to be more precisely integrated, opening a new spectrum of questions to terrestrial paleoecologists.