ABSTRACT

The Birdtail-Waskada zone in southwestern Manitoba is a north-south aligned, 20 to 35 km-wide region characterized by numerous structural and stratigraphic irregularities in Paleozoic strata, most of which are associated with dissolution of Middle Devonian Prairie Formation salt. Salt dissolution features differ in style and scale, reflecting spatial and temporal variations in dissolution processes. Part of the Middle Devonian and Ordovician sections reveal anomalous depositional and diagenetic features. The eastern margin of the zone coincides with the western margin of the Middle Devonian (Winnipegosis) carbonate shelf.

The Birdtail-Waskada salt dissolution zone, as mapped from seismic reflection and well data, directly overlies the Precambrian Churchill-Superior boundary zone as identified from gravity, magnetic and electromagnetic data. Seismic data indicate the basement surface within the boundary zone is disrupted by faults and a regional hinge line.

The Phanerozoic history of the Birdtail-Waskada zone appears directly linked to instability along the Churchill-Superior boundary zone and the related differential subsidence of adjoining crustal blocks. In particular, activation of basement faults probably affected the regional hydrodynamic system and its influence on dissolution of Devonian salts.

The stratigraphic, structural and diagenetic anomalies in the Paleozoic strata of the Birdtail-Waskada zone may have enhanced the petroleum potential.