Structure of Coleville-Buffalo Coulee Area, Saskatchewan
Contour maps, a paleogeological map, and cross sections are presented to demonstrate the structure of the area. Lower Paleozoic structure is briefly discussed. All structures observed in the uppermost Devonian and Lower Mississippian strata are attributed to leaching of a thick Upper Devonian anhydrite member with consequent collapse of overlying beds. The drainage pattern of an old land surface developed by a post-Mississippian erosional period is outlined, and all structures in the Cretaceous are shown to be the result of compaction and draping over this old land surface. The limitations this erosional unconformity place on seismic interpretations are explained. Unconformable contact between the Mississippian Coleville sand and Cretaceous shale probably accounts for the entrapment of oil in the sand.