Abstract

Nearly 1,450 resistivity geophysical well logs were correlated over 758 square miles and their stratigraphic information was incorporated with core data to objectively study the geological section from the surface to a depth of nearly 1,950 ft.-deposited during the final retreat of the Western Interior Cretaceous Sea (WICS). This information was utilized to make new interpretations about both the geological and structural events that developed in this area. This included the effect volcanic ash deposition had on the ultimate development of the Boulder- Weld Fault Zone (BWFZ) and the division of this feature into a compressional structural eastern area and a western area comprised of both compressional and extensional features. A stratigraphic correlation of the Fox Hills Sandstone in the western portion of the study area facilitated a detailed structural reinterpretation of its outcrops there.