Lithotype (maceral) composition and variation as correlated with paleo-wetland environments, Gates Formation, northeastern British Columbia, Canada

Abstract

Lithotype samples collected from mid-Albian Gates Formation coal seams in northeastern British Columbia, were analysed in order to gain a better understanding of coal facies variation. Compositional boundaries between lithotypes are gradational. From bright to dull coals, there is a progressive decrease in vitrinite and increase in inertinite. Liptinite is negligible (<1%); the dull appearance of some of the lithotypes is due to inertinite content and, to a lesser extent, degraded vitrinite. The lithotypes represent a broad spectrum of depositional environments from forest swamps to dry, herbaceous and/or shrubby marshes. Compositional differences between lithotypes are due to vegetational characteristics as well as differences in the rate of accumulation and decomposition of plant communities. Lateral and vertical variation in lithotype composition was controlled by groundwater levels (due to sea level variations and climatic conditions?) and proximity to active fluvial systems. The coals formed on broad, low relief coastal plains. Forest swamps were dominated by coniferous trees with a significant component of ferns as herbs or low trees. Angiosperms and cycads contributed to the vegetation in the form of shrubs. Angiosperms were probably also present as marginal herbs.