ABSTRACT

The Devonian rock sequences of Saskatchewan are sparsely fossiliferous, particularly in the eastern regions and adjoining parts of Manitoba and the United States. The relatively low diversity faunas attest to strong restrictive influences in the southeastern lobe of the western Canadian seaway. Due to the equatorial, or near equatorial, position of the sedimentary basin and the absence of any major influences from land, an autochthonous sedimentary package developed to which the principles of sedimentation in an epeiric sea can be ideally applied.

Stratigraphic studies and correlations have been based mainly on rocks and rock sequences, with all their complications and limitations. Fossils have rarely been used for this purpose, and during a century of study a crude biostratigraphic framework emerged more by accident than design. Biostratigraphy as a tool for correlation has not yet been sharpened to develop a cutting edge.

Of known fossil occurrences, ostracodes appear to be the most numerous and varied in the Middle and Upper Devonian rock sequences of Saskatchewan. Several assemblages are recognized and referred to the standard zones of western Canada. Although not as richly and continuously developed as are their counterparts in northern Alberta and the Northwest Territories, where open-marine conditions prevailed, ostracodes nevertheless tie segments of the Saskatchewan Devonian rock sequences into the overall western Canadian biostratigraphic framework.

Presumably, ostracode-rich beds yielding an open-marine fauna are evidence of major transgressive pulses. Conversely, the ostracode-poor or unfossiliferous sequences attest to stagnant, or even regressive influences. The presence of some ostracodes of eastern stock indicates that during part of Dawson Bay time and for a very short interval in the late Mid-Givetian, the western and eastern Devonian seaways must have joined, exchanging water masses in western Manitoba and eastern Saskatchewan. This connection has been intermittently discussed but never defined in geological literature.

Unconformable relationships across the Middle and Upper Devonian boundary are discussed in the light of ostracode and conodont evidence.