Petrography and depositional environment of the No. 308 coal seam (Upper Silesian Coal Basin, Poland)—a new approach to maceral quantification and facies analysis

Oriented block samples of coal representing the lower layer (2.1 m) of the No. 308 coal seam were collected in the Ziemowit mine. Microscope investigations were carried out using a self-developed, fast method of maceral quantification that enables obtaining a continuous petrographical profile (“microprofile”) of a seam and computer processing of the data. The contents of macerals and maceral groups distinguished along the profile were averaged using the method of moving averages to show trends of environmental changes in a mire. The facies diagram proposed is based on an assumption that oscillations of water table in the mire affect the coal petrographical composition, while stronger water influxes into the mire increase the mineral matter content of coal. The author has identified three major types of the mire environments in which plant material was deposited during deposition of the No. 308 coal seam. These are permanently inundated = planar mire (PM) with two sub-environments—PM “margin” and PM “central”; temporarily inundated = transitional mire (TM) with two sub-environments—TM “wet” and TM “dry”; and elevated = domed mire (DM) with two sub-environments—DM “progressive” and DM “regressive”.