ABSTRACT: Microfossil-based Upper Cretaceous Stratigraphy of the California Standard C. & E. Cow Creek 6-30-8-1W5 Well: Implications for Structural Sections in the Triangle Zone, Southern Alberta

WALL, JOHN H., Geological Survey of Canada, Calgary, Alberta, Canada, and DONALD K. NORRIS, Geological Consultant, Kelowna, British Columbia, Canada

The California Standard C. & E. Cow Creek Well is located at the apex of the Triangle Zone along the eastern boundary of the Foothills. It penetrated 14,382 ft (4384 m) of Cretaceous and Jurassic rocks before reaching autochthonous Mississippian carbonates with no hydrocarbon shows to total depth 14,905 ft (4543 m). Megascopically, the Triangle Zone is a north-trending trigonal prism with its base above the undeformed carbonates, its east flank defined by the Waldron Fault, and its west flank by the Bridge Fault. Mesoscopically, the Triangle Zone is acutely deformed, with anomalous thickening of the Upper Cretaceous formations identified in the Cow Creek well, as well as in outcrop sections along Todd Creek and Crowsnest River.

In the well the St. Mary River Formation is present from near surface to 6035 ft (1839 m), implying an excessive thickness probably resulting in part from faulting. There follows an expected section of Bearpaw and Belly River formations overlying a thin section of Wapiabi Formation. From 9010 to 10,483 ft (2746 to 3195 m), two thin thrust repeats of the Belly River are separated by a second thin occurrence of Wapiabi. From 10,050 ft (3063 m) downward, the sequence appears normal. Thus, the basal detachment for Foothills deformation and the Triangle Zone occurs in the basal Belly River and in the upper Wapiabi, as illustrated in a revised regional structure section.

AAPG Search and Discovery Article #91012©1992 AAPG Annual Meeting, Calgary, Alberta, Canada, June 22-25, 1992 (2009)