Preliminary Map No. 57: Geology of the Butler Ridge Area
View Map (PDF, 2.1 MB), (1:50 000)
Notes (PDF, 801kB)
Preliminary Map 57 presents the geology of the Butler Ridge area, which includes approximately 500 square kilometres of area north and south of Williston Lake near the W.A.C. Bennett dam site in northeastern British Columbia. The map shows borehole locations, geology, and structure. The accompanying notes describe the general stratigraphy, coal geology, the pre-Cadomin unconformity, and structural relationships. The area is underlain by rocks of the Monteith, Beatty Peaks, Monach, Cadomin, and Gething Formations.
Thinning and facies changes occur across the Carbon Creek fault. The Jurassic to Lower Cretaceous Monteith Formation of the Minnes Group consists of a 50-metre interval of quartz arenite in the area. Thickness of Minnes Group strata between the Monteith and Cadomin formations thins dramatically from about 990 metres in the Carbon Creek area southwest of the fault, to 145 metres in the Butler Ridge area. In Carbon Creek area, Minnes Group rocks above the Monteith Formation are the Beattie Peaks Formation shale, the Monach Formation arenite, and the Bickford Formation arenite and shale. In the Butler Ridge area, thinning prevents lithostratigraphic subdivision. The section consists of interbedded arenites and siltstones with no persistent markers.
The Cadomin Formation contact with the Minnes varies from gradational in the west to sharp in the east. The Cadomin is dominantly pebbly arenites and conglomerates. Gething Formation rocks overlie the Cadomin and are the main coal-bearing strata.
A major fault on Mount Gething dips 25 degrees near surface and steepens to near vertical at depth. Hangingwall strata form a box anticline with the west limb cut off by the fault.
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