The middle Eocene Márkushegy subbituminous coal (Hungary): Paleoenvironmental implications from petrographical and geochemical studies

The predominance of angiosperms in the peat-forming vegetation of the Márkushegy coal is evidenced by the high relative proportions of angiosperm-derived triterpenoids. The influence of the relative proportion of fossil wood on tissue preservation (TPI) is indicated by the positive relationship of the concentration of land plant-derived terpenoid hydrocarbons and TPI. The degree of gelification of plant tissue (GI) is governed by the microbial activity in the mire, as indicated by a negative relationship between GI and the steroids/hopanoids concentration ratios. The variation of the δ13C values of coal is obviously governed by the relative contribution of plant lipids to the biomass. The obtained negative relationship between δ13C of the coal and GI is explained by the effect of cellulose decomposition and microbial activity on the isotopic composition of the organic matter.