- GeoRef, Copyright 2004, American Geological Institute.
The Upper Cretaceous in the southern Alberta Foothills is represented almost entirely by clastic sediments with a maximum thickness of about 14,000 ft (4270 m). This essentially uninterrupted sequence, in which all stages from the late Cenomanian through the Maestrichtian are represented, consists of alternating phases of marine, littoral or deltaic, and continental deposition. In ascending order, the major rock units consist of the Alberta Group (Blackstone, Cardium and Wapiabi Formations), Belly River, Bearpaw, Blood Reserve, St. Mary River and Willow Creek Formations. Of these units, the Blackstone, Wapiabi and Bearpaw are predominantly shale and marine in origin the Cardium, Blood Reserve and lower part of the St. Mary River are somewhat arenaceous and represent littoral to deltaic regimes; the Belly River, most of the St. Mary River, and the Willow Creek consist of varying proportions of shale, siltstone, and sandstone, and were deposited mainly under continental conditions. A succession of 11 microfaunas is recognized in the Alberta Group and Bearpaw Formation. In order of decreasing age, with indicated environments in parentheses, these are the lower pelagic (outer shelf to upper bathyal) and Pseudoclavulina sp. (nearshore) in the Blackstone Formation; the Trochammina sp. 1 (nearshore), "Anomalina" (inner shelf), Brachycythere-Bullopora (inner shelf), Anomalinoides henbesti (middle shelf), upper pelagic (middle to outer shelf) and unnamed agglutinated (nearshore) in the Wapiabi Formation; and ostracode (supralittoral), arenaceous foraminiferal (nearshore) and Gavelinella talaria (offshore) in the Bearpaw Formation.