Depositional Setting and Coal Petrology of Tulameen Coalfield, South-Central British Columbia

Abstract

The Tulameen coalfield of south-central British Columbia lies in an open-folded, south-southeast plunging syncline within the Cordilleran intermontane belt. Several seams of coal are present within the middle member of the Allenby Formation (Princeton Group) of Eocene age. The upper, or main, coal seam, about 15 to 21 m thick, is exposed on the southwestern limb of the syncline where it is relatively undisturbed by structural deformation. The coal is predominantly vitrain and clarain and is composed of more than 90% vitrinite. Vitrinite reflectance increases from 0.62% in the north to 0.86% in the south but shows no significant vertical variation. Coal rank ranges from high-volatile C to high-volatile B bituminous. Clean coal has 14% ash (mostly kaolinite and quartz) and is low in sulfur. The number of interbedded bentonite, mudstone, and shale partings decreases from north to south. These partings are rich in smectite and/or kaolinite. Macerals in the coal suggest that the coal-forming peat accumulated in a predominantly forest-moor-swamp environment. Similarities in other floras of the same age in the western Cordillera indicate that equitable climates were widespread and that the Coast Mountains and Cascade Range were much lower than at present. An abundance of tephra and bentonite indicates that volcanic activity was contemporaneous with coal and sediment deposition.