- GeoRef, Copyright 2004, American Geological Institute.
Permian Ishbel Group lithologies in southwestern Alberta and southeastern British Columbia are the products of depositional environments similar to those of the Phosphoria Formation in the western United States. In the study area, the Ishbel Group consists of up to four distinct subdivisions: the Johnson Canyon, Telford, Ross Creek and Ranger Canyon Formations. In eastern, Front Range sections, the Ishbel Group is normally expressed as undifferentiated, thin, erosional condensed sequences (McGuan 1965) ranging in thickness from a few centimetres to several metres. These condensed sequences contain multicycled Permian components, and thin eastward (landward) across the Permian shelf edge. The Ishbel Group was deposited under conditions of warm, arid climate, shallow water, low-energy shorelines and low hinterland relief. Lateral movement about a north-northwest to south-southeast trending depositional hingeline resulted in minor transgressive and regressive cycles, evidenced by the cyclic nature of lithologies and the presence of paraconformities. Structural relationships within the Ishbel Group are complex, partly because of the presence of several distinct faulting styles. Anomalously thick sections within the Telford thrust plate may be due in part to a reactivated northeast-to-southwest trending fault, with downthrow to the north. Phosphatic horizons within the Ishbel Group show economic potential as sources of phosphate, and associated minerals.