| The 81 Ma Shannon Sandstone is an important oil producer in the Powder River Basin, Wyoming, and as such, has been the focus of many stratigraphic studies. These studies have produced multiple, discordant depositional models for the Shannon Sandstone and more research is needed to resolve its origin and improve characterization of this important reservoir. This study synthesizes information gathered from additional core analysis, previously unstudied outcrops, x-ray diffraction (XRD) analysis, petrographic analysis, additional geophysical data, and additional cross sections from well-logs and outcrops with published data (see plates 1--3, in the supplementary files, for cross sections). For example, previously undocumented bidirectional paleocurrents, and distinct lateral changes in grain size should be integrated into the Shannon Sandstone depositional model. Although we do not claim to entirely solve the "Shannon Sandstone enigma", these new data confirm tidal influence and suggests a definite direction of progradation. With these new data, we can now test the likelihood of depositional models that vary from shelf sand ridge complexes to lowstand shorefaces to tide dominated deltas. Furthermore, because the Shannon Sandstone is analogous to other, little understood, hydrocarbon reservoirs throughout the Rockies and around the world insights gained from the Shannon Sandstone can be applied to exploring for and producing hydrocarbons from similar deposits. |
