Reports: AC8
47277-AC8 Vitrinite Reflectance, Basin Thermal History, and a Link to Seafloor Methane Seeps, Cretaceous Western Interior Basin, United States
This annual progress report is part of a comprehensive assessment of organic matter maturation in the Cretaceous Western Interior Basin of North America, specifically by vitrinite reflectance analyses, aimed at understanding basin thermal history and evolution. The overall strategy of this assessment has been to collate existing data and generate new data where stratigraphic and geographic gaps exist in our compilation of vitrinite reflectance data.
As reported in our last annual report, we have made good headway collecting and preparing samples for vitrinite reflectance - at this time, a total of ~170 samples are now in our collection, a nearly 5 fold greater number than proposed in our original project.
The project involves a compartmentalization of Cretaceous strata into three divisions: Albian-Cenomanian, Turonian-Santonian, and Campanian-Maastrichtian. Our field and core lab work, focused on filling stratigraphic and geographic gaps in our existing data compilation and building west-to-east transects across the basin, resulted in 44 new and unique samples for the Albian-Cenomanian time interval in Colorado, Montana, Wyoming, Utah, New Mexico, Nebraska, Kansas, South Dakota and Iowa. For the Turonian-Santonian stratal division, 25 new and unique samples were obtained in Colorado, Wyoming, Utah and Kansas, whereas 14 new samples from Colorado, Wyoming, Utah and Nebraska were found for the Campanian-Maastrictian interval.
We have since begun vitrinite reflectance analyses that are ongoing. Preliminary results suggest that the sheer size of our sample set will allow regional trends to be established - that is, our original data compilation from the literature was difficult to understand and interpret primarily because much of the published data was derived from samples proximal to igneous intrusions and faults, whereas our sampling effort deftly avoided such geologically disturbed environments so we could determine a regional geothermal gradient for the basin. A no-cost extension was requested and granted to support a final year of graduate student effort to complete the reflectance analyses and a manuscript for publication.
