Upper Jurassic and Basal Cretaceous Sandstones of Southern Saskatchewan and Vicinity: ABSTRACT

Abstract

The Roseray Formation ranges in age from Callovian in the west to Oxfordian(?) in the east and is correlative with the upper part of the Rierdon Shale. Well-sorted quartzose sandstone beds (clinobeds) sloping eastward and southward constitute the formation. Grade size of the clinobeds and kaolin (up to 10% as matrix and laminae) decrease downslope in inverse relation to illitic clay and accessory glauconite. Thickness ranges between 45 and 160 ft for the formation and up to 70 ft for a particular clinobed. The clinobeds are imbricated west to east and resemble marine spits linked to an eroded easterly migrating northern delta. The Cantuar Formation (Aptian to Albian) comprises (a) white to light-gray quartz-kaolin (feldspathic) arenites; (b) olive-green to dark-gray speckled biotite-chlorite, and argillaceous (feldspathic) quartz-arenites; and (c) dark-gray and gray-black carbonaceous-lignitic mudstone and argillaceous quartz-arenites. Both (a) and (b) grade into (c). Generally bimodal, the arenites range from fine to coarse grained with abundant grit and intraformational conglomerate, but are dominantly coarsely fine and medium. They are mudstone indurated, earthy, and characterized by heterogeneity of crossbedding types, grain size induration and unit thickness, all attributable to fluviatile channel deposition. The carbonaceous facies reflects overbank and floodplain swamp-lacustrine sedimentation. The q artz-kaolin facies apparently blankets a broad low-relief topography on the Upper Jurassic beds, whereas the biotite-chlorite facies belongs to a later valley system entrenched on the former. The Roseray oil reservoirs are in the updip mesas, buttes, and escarpments cut into the Roseray Formation and isolated by impervious Cantuar lithologies. Oil is also produced from permeable Cantuar quartz-kaolin sandstones overlying these features. End_of_Article - Last_Page 535------------