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The AAPG/Datapages Combined Publications Database

CSPG Special Publications

Abstract


Petroleum Geology of the Cretaceous Mannville Group, Western Canada — Memoir 18, 1997
Pages 191-210

Evolution of the Lower Cretaceous Mannville Sedimentary Basin in Saskatchewan

J. E. Christopher

Abstract

The Mannville sedimentary basin in Saskatchewan was activated by a Late Jurassic to Neocomian reorganization of the marine Jurassic setting centred on the Williston Basin and its western arm to the Rocky Mountain Geosyncline through the Belt-Big Snowy Trough of central Montana. Uplift of the Swift Current Platform in southwestern Saskatchewan coincided with subsidence of the intervening Punnichy Arch of eastern Saskatchewan. The last event removed the barrier to a Mannville trough trending southeasterly from central Alberta, and made possible its extension into the Williston Basin along the axis of a predecessor Middle Devonian Elk Point Basin.

The Mannville sedimentary pattern was woven by an interplay of marine, estuarine and fluviatile agents acting in a setting controlled by paleotopographic relief and eustatic and tectonic changes in relative sea-levels. Sediments came from local land forms, the Precambrian Shield and from rising volcanic uplands of the Rocky Mountain geosyncline of western Montana. The Lloydminster, Rex and Waseca members are dominated by upward coarsening sedimentary facies associations. Full-section sand sheets of these members are conspicuous in southeastern and west central Saskatchewan, where they reflect input from outcrops of the Success Formation, and buildup and coalescence of off-shore and shoreface deposits generally elongated to the northwest. In the General Petroleums and Sparky members these facies are concentrated north of the Punnichy Arch and in conjunction with widespread Sparky coal beds in western central Saskatchewan, indicate the Mannville basin at maximum regression.

Narrow estuarine and fluviatile channel deposits of the Lloydminster, Rex and Waseca members intersect the sand sheets and meander for lengths up to 90 km. These deposits are survivors of truncation by succeeding transgressive strands. On the other hand, General Petroleums and Sparky channel sandstone bodies, are distributed across central Saskatchewan and indicate fluviatile input and strand alignments across and along a renascent Punnichy Arch. Mudflats blanket the Arch in the Lloydminster and Rex members and the Williston Basin region to the south in the Sparky and General Petroleums. Waseca mudstones, representative of tidal mudflats, flank eastern slopes of the Swift Current Platform in southwestern Saskatchewan. The dominance of shale in the Lloydminster Member of northwestern Saskatchewan reflect facies of the deeper Clearwater basin.

Uplift of the Punnichy Arch terminated Cantuar deposition. Erosional planing of Cantuar sediments on the Arch accompanied a southerly tilt and episodic subsidence of the Swift Current Platform into an expanding northern arm of the Big Horn Basin of Wyoming. Rise of sea level expanded the succeeding Pense seaway across Saskatchewan. Offshore deposits accumulated to maximum thickness on the Swift Current Platform apparently from recycled Cantuar sediments. In west-central Saskatchewan equivalent strata (McLaren, Colony) remained a mixed shoreline and backshore facies.


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