Stratigraphy and structure of Pleistocene collapse in the Regina Low, Saskatchewan, Canada

Abstract

The Regina Low is a collapse structure, formed as a result of dissolution of salt from the Middle Devonian Prairie Evaporite Formation. In this study, collapse has affected the Upper Cretaceous Pierre Shale and the Ardkenneth and Snakebite members of the Bearpaw Formation of the Montana Group; the Mennon, Dundurn, and Warman formations of the Sutherland Group; and the Floral and Battleford formations of the Saskatoon Group. A structural closure of 125–175 m approximates the thickness of the Middle Devonian Prairie Evaporite Formation. In the Early Pleistocene, about 54 m of collapse took place in eastern Regina accounting for the preservation of Snakebite Member. Major collapses of about 58 and 86 m took place in northern Regina during deposition of Middle Pleistocene, pre-Illinoian Dundurn Formation. The final major collapse of about 127 m took place in northeastern Regina between deposition of the lower and upper tills of the Floral Formation. Eighty-seven metres of this collapse took place during deposition of the Late Pleistocene, interglacial, Sangamon Pasqua Member of the Floral Formation. The Pleistocene fill in the Regina Low collapse structure suggests that collapse took place when dissolution of salt from the Prairie Evaporite Formation was accelerated by high hydraulic gradients created by the surcharge pressures of the glaciers.