Application of Sequence Stratigraphy to Solve the Depositional History of Quartz Arenit Reservoir Rocks in the Mississippian Carbonate Succession of the Northern Williston Basin, Southeastern Saskatchewan

Donald M. Kent
D.M. Kent Consulting Geologist Ltd, Regina, SK

An influx of quartz sand onto a carbonate terrain and into a carbonate-depositing sea of the northern Williston Basin during a Late Osagian low-stand has produced a variety of sandstone bodies that are collectively identified as the Kisbey Sandstone. These bodies have prompted geologists to postulate a diversity of depositional environments for their origins. Foremost among these is a fluvial setting in which the thicker quartz sand bodies are identified as channel-fill deposits. However close examination of borehole core reveals a distinct absence of features representing fluvial sedimentation. Instead the rocks are more likely the result of deposition in sabkha, coastal and proximal-offshore environments, that existed during the Late Osagian low-stand. The sand body morphologies suggest: 1) thin sheet sands covering residual soils formed on to a carbonate bedrock, representative of a coastal sabkha; 2) coastal dune sands overlying or merging with the sheet sands; 3) littoral sand bodies forming beach or offshore bars during initial stage of flooding; 4) tidal channel deposits, truncating the sheet sands and residual soils; and 5) thick structureless bodies of quartz sand that may represent subaqueous accumulations originating from an aeolian source.

Since the sheet sand deposits and their marine equivalents, sandy and argillaceous dolomites, make up the largest proportion of the Kisbey, finding the potentially more productive sand bodies approaches serendipity. However, employing principles of sequence stratigraphy to help predict the location of the low-stand coastline could greatly confine the area of exploration.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005