ABSTRACT

The oil-producing Cardium Formation of the Crossfield-Garrington area includes two, long, narrow, en echelon sandstone bodies, extending northwesterly from Calgary for approximately 120 miles. The sandstone reaches a maximum thickness of 20 feet and lies at depths of between 5500 and 7500 feet.

The two sandstone bodies have many features similar to those of recent offshore bar deposits. Transverse cross-sections indicate that the sandstone bodies have a lens-like form, with a nearly flat base and a convex upper surface. The shape is asymmetrical with a gentle west slope and a steep east side. The eastern margin of the bodies is slightly sinuous and the western edge nearly straight or gently curved.

The bodies are interpreted as offshore bars which formed along the western margin of the Turonian (early Late Cretaceous) seaway. The sediments were derived from a rising borderland to the west and deposited by the action of waves and near-shore currents. The sandstone bodies were preserved by a widespread marine transgression, with subsequent deposition of the overlying black shale.