Chapter 124: Regional Geology of the Windermere Supergroup, Southern Canadian Cordillera and Stratigraphic Setting of the Castle Creek Study Area, Canada

Abstract

Abstract The Windermere Supergroup (WSG) represents nearly 9 km (5.5 mi) of Neoproterozoic sedimentary rocks that predominate the exposed geology within the western Main Ranges and Omineca belt of the southern Canadian Cordillera. The WSG comprises two main stratigraphic ensembles: siliciclastic and subordinate carbonate and mafic volcanic rocks deposited during extensional tectonic activity (rifting), and a more widespread succession of siliciclastic strata, composed largely of turbidites deposited during passive-margin sedimentation. Stratigraphic reconstruction of the passive-margin component of this depositional system suggests that the turbidites are part of a single depositional system that may have been comparable in scale to the modern Amazon and Mississippi fans. Several key stratigraphic markers are traced throughout the outcrop belt and are used to reconstruct a synoptic view of this depositional system. The Castle Creek study area in the northern Cariboo Mountains represents some of the best-exposed and well-preserved strata of the Windermere turbidite system. The Upper Kaza Group consists of more than 800 m (2624 ft) of sand-rich turbidites deposited in a weakly channelized environment on the basin floor; it represents some of the most basinal facies preserved. The overlying mud-rich Isaac Formation consists of six channel-levee complexes and several spectacular mass-transport complexes deposited in a slope setting. The vertical transition from basin floor to slope is interpreted to represent slope progradation into the margin in response to decreased rates of thermally driven subsidence. The regional stratigraphic framework that has been established for this study area and the Windermere turbidite system holds tremendous potential as an analog for improved understanding of modern turbidite system at the regional as well as subseismic scale.