Paleoceanographic evolution of the Late Devonian Duvernay Formation : insights from the geochemistry of the Western Canada Sedimentary Basin.

The Late Devonian Duvernay Formation is characterized by organic-rich mudrocks, argillaceous carbonates, and calcareous shales and is located in the Western Canada Sedimentary Basin (WCSB). The Duvernay is partitioned into the West and East Basins by the Leduc Formation carbonate platform along the Rimbey-Meadowbrook trend. This study identifies intervals of organic matter accumulation associated with elevated productivity in a high resolution geochemical analysis of four cored wells in the Duvernay. These geochemical analyses demonstrate the paleoceanographic history of the Duvernay through utilization of major and trace elements, isotopic composition of organic matter, and organic matter abundance. As a result, five chemostratigraphic units are present representing intervals of anoxia punctuated by oxic intervals. Low nitrogen isotopic composition across the WCSB indicates that nitrogen fixation was the dominant nutrient pathway, suggesting that an open marine hydrographic setting with coastal upwelling controlled organic matter supply during deposition of the Duvernay Formation.