Rocky Mountain (56th Annual) and Cordilleran (100th Annual) Joint Meeting (May 3–5, 2004)

Paper No. 6
Presentation Time: 10:40 AM


BEATTY, Tyler W., Applied Stratigraphy Research Group, Department of Geology and Geophysics, University of Calgary, Calgary, AB T2N 1N4, ORCHARD, M.J., Geol Survey of Canada, 101-605 Robson St, Vancouver, BC V6B5J3, Canada and HENDERSON, Charles M., Applied Stratigraphy Research Group, Department of Geology and Geophysics, Univ of Calgary, 2500 University Drive, NW, Calgary, AB T2N 1N4, Canada,

Upper Paleozoic to Lower Mesozoic strata in south-central British Columbia provide a long-term record of deposition and tectonism in the Quesnel Terrane, the easternmost of the “suspect” terranes of the Canadian Cordillera. The Quesnel Terrane in the Kamloops region comprises three successive island-arc related successions of Devonian to Jurassic age, the Harper Ranch, Nicola, and Rossland groups. The Harper Ranch Group represents the stratigraphic base of the Quesnel Terrane in the area.

The lower part of the Harper Ranch Group comprises the Tk’emlups Formation and the conformably overlying South Thompson Formation. The main part of this succession was deposited between the Lower Tournaisian (duplicata Zone) and Serpukhovian (bilineatus Zone, sensu lato) although locally it may be as old as Early Famennian (triangularis Zone) based on conodonts recovered from conglomerate. This succession is interpreted to represent the development and subsequent infill of an island-arc marginal basin. The McGregor Creek Formation comprises the upper part of the Harper Ranch Group and records carbonate deposition on a slowly subsiding platform during Asselian to Wordian. These successions are separated by an unconformity in which the Pennsylvanian is missing.

Conodont and ammonite collections from the overlying Mesozoic successions provide evidence for the duration of the Nicola Group and aid the identification of an unconformity between Triassic and Jurassic strata in the area. This unconformity can be traced north and south within the Quesnel Terrane and is coincident with an eastward migration of the axis of arc magmatism.

Comparison of the tectonostratigraphic record of the Quesnel Terrane with those of other Cordilleran terranes, such as the Yukon-Tanana, Stikine, Chilliwack, and eastern Klamath terranes, demonstrates broad trends in the timing of major unconformities and suggests their development in a common tectonic regime.