Abstract

Devonian rocks underlie the southern half of Saskatchewan and the southwestern half of Manitoba. They are mainly Middle and Late Devonian in age and lie with angular unconformity on strata ranging in age from Late Ordovician to Middle Silurian. Strata directly overlying the lower Palaeozoic beds may have been formed between Late Silurian and early Middle Devonian times.

During Devonian time Saskatchewan and Manitoba were part of the stable cratonic shelf and were affected only by minor epeirogenic movements. The Middle Devonian rocks — Eifelian to Givetian — were deposited in a northwest-southeast trending trough surrounded on three sides by land areas of low relief and connected to the open sea in the northwest. The rocks are a rhythmic sequence of limestones (including thick organic accumulations) and evaporites (anhydrite, halite and potassium salts). The sediments of Frasnian age were deposited in an extensive shelf sea covering all of southern Saskatchewan and southwestern Manitoba and extending southward into the United States and westward into eastern Alberta. The rocks are mainly limestones with thin interbedded anhydrites, occasional halites and calcareous shales. The strata of Famennian age were formed in a near-shore, tidal-flat environment and contain numerous brecciated zones, representing intraformation unconformities, marking fluctuations of sea level.

The significant fossils found in the Devonian rocks of the study area include Stringocephalus in Givetian strata, Eleutherolcomma in Frasnian formations, Cyrtiopsis and Cleiothyridina in Famennian beds and Atrypa from the base of the Devonian to the youngest (late Middle) Frasnian strata.