Organic petrology of Hat Creek coal deposit No. 1, British Columbia

Abstract

The upper Eocene Hat Creek coal deposits of British Columbia, Canada, are one of the thickest lignite to subbituminous coal deposits of the world, and comprise 350–550 m of coal. Samples of sedimentary organic material were taken from a 560-m interval of interbedded shale, siltstone and carbonate that was penetrated by corehole 75–106 in the centre of the coal basin, and the reflectances of huminite (eu-ulminite) from coal and kerogen from the organic material were determined and petrographical analyses were made. The coal deposit contains many leaf- and resinite-rich horizons, and the reflectance of huminite in these horizons in lower than in corresponding horizons containing less liptinite. When compared with huminite in adjacent coal beds, the reflectance of huminite in shale is lower, that in siltstone is similar, and huminite associated with carbonate rocks has slightly higher reflectance values. The petrological variation in the coal is mainly within the huminite group of macerals. The coal at the top of the deposits is lignite (% R o = 0.38) and becomes subbituminous C (% R o = 0.50) at the base. The inertinite content is very low, indicating a low level of peat fire or oxidation. The early stages of transformation of gelinite to macrinite are described. The paleoenvironment appeared to be lacustrine, as determined by organic petrological analysis of coals and interbedded sediments. Four major zones, each containing many subzones, were found. Paleoenvironments were similar for the A and C zones and also for the B and D zones.