The burial history of the eastern margin of the Powder River Basin, WY, as interpreted from Late Cretaceous aged rocks

Economic energy resource development is dependent on the intrinsic understanding of the geologic evolution of a sedimentary basin. This geologic evolution is recorded by changes to the sedimentary rock during burial (i.e. diagenesis) and often can only be identified on a microscopic scale. This study analyzes diagenetic changes of the Late Cretaceous Turner Sandstone, a major hydrocarbon reservoir in the Powder River Basin, WY, USA. Samples were collected from outcrops along the Black Hills, WY, to be compared with the burial history of the central Powder River Basin. These samples were thin-sectioned and analyzed with a petrographic microscope and a scanning electron microscope. Results from this analysis show the formation of quartz overgrowths, calcite cements, kaolinite, and albitization, which is the change from potassium to sodium in feldspars. Ordering these observations based on cross-cutting relationships resulted in a relative time series (i.e. paragenetic sequence). This paragenetic sequence indicates that the Black Hills underwent deep burial after the deposition of the Turner Sandstone to a depth similar to the current basin center. This work contributes to a better understanding of the microscopic features of the Turner Sandstone and therefore helps define the basin evolution of the Powder River Basin. These results can be used to improve basin modeling and reservoir characterization. Improvements on this scale can have implications on the reduction of greenhouse gas emissions and energy security.