About This Item

Share This Item

The AAPG/Datapages Combined Publications Database

Williston Basin Symposium

Abstract

SKGS-AAPG

Eighth International Williston Basin Symposium: Core Workshop Volume, October 21, 1998 (SP13A)

Pages 89 - 104

Occurrences of the Middle Devonian Ratner Laminite in the distal part of the Elk Point Basin, southern Saskatchewan

J. JIN, Department of Earth Sciences, University of Western Ontario, London, ON
K.M. BERGMAN, Department of Geology, University of Regina, Regina, SK.

ABSTRACT

The Ratner laminite, which typically consists of three cycles of finely laminated, dolomudstone-interlaminated dolomite and anhydrite-bedded, nodular anhydrite in the northern Saskatchewan Sub-basin (Saskatoon-Quill Lake area), is sandwiched between the Middle Devonian Winnipegosis Formation and the Prairie Evaporite. In the southern Saskatchewan Sub-basin, however, the Ratner laminite has not been investigated in detail and has been poorly understood. Our preliminary study of the Winnipegosis carbonate-Prairie Evaporite succession in the Macoun-Hitchcock-Estevan area demonstrates that the Ratner laminite is more widespread than previously thought. All three of the Ratner facies (basinal, reef-slope, reef-top) that have been recognized in the northern Saskatchewan Sub-basin are present in the southern area. The three dolomite-anhydrite cycles, which are characteristic of the northern Ratner laminite, occur in at least one well (12-27-4-9W2) in the southern area. The southern Ratner laminite is best developed in areas adjacent to relatively large pinnacle reefs, especially between closely clustered pinnacles. Deposition of the laminite is interpreted to have been associated with dissolution of the Winnipegosis reefs during evaporative drawdown. Compared with the northern Ratner, the southern laminite shows a number of distinct features: 1) a much darker grey colour because of its greater proportion of organic-rich partings, 2) more pervasive development of fine, crinkly lamination (cryptalgal structures), 3) considerably less common enterolithic anhydrite beds, 4) more common calcitization of anhydrite, whereby anhydrite laminae were altered to coarse-grained white dolomite, 5) less common occurrences of strongly contorted, interlaminated dolomite and anhydrite caused by displacive anhydrite growth under near desiccation conditions and, 6) predominance of a single-cycled laminite succession. Most of these characteristics, especially the darker-grey colour and general lack of multiple cycles, are interpreted as the result of deposition of the laminite in a relatively deeper-water setting in the southern part of the Saskatchewan Sub-basin, where more frequent and prolonged plankton blooms and fewer desiccation episodes would have prevailed.

Pay-Per-View Purchase Options

The article is available through a document delivery service. Explain these Purchase Options.

Watermarked PDF Document: $14
Open PDF Document: $24