Marine Jurassic Formations of Southern Alberta Plains

Abstract

The Jurassic sediments of the Southern Alberta Plains, known only from subsurface work, are described as to lithology, thickness, distribution, stratigraphic relationships, and geologic history. The three-fold subdivision of the Ellis group into Swift formation, Rierdon formation, and Sawtooth formation, established in Montana, is recognizable and applicable in Alberta. A major unconformity between the Jurassic beds and the underlying Paleozoic limestone influences the distribution of the Sawtooth formation. Late Jurassic or early Cretaceous erosion truncating the Jurassic formations from south to north has determined the present extent and northern boundaries of these formations in Southern Alberta.