Maceral and geochemical characteristics of coal seam 1 and oil shale 1 in fault-controlled Huangxian Basin, China

Abstract Seven samples of coal seam 1 and oil shale 1 from the fault-controlled Hangxiang Basin have been analysed by coal petrographic and geochemical methods. High huminite ratios and high contents of sesquiterpenoids and diterpenoids indicate that coal seam 1 and oil shale 1 are predominantly composed of terrestrial higher plant material. Two ternary diagrams of “facies diagnostic” macerals and biomarkers were used to interpret the depositional environments of organic matter in coal seam 1 and oil shale 1. In both diagrams coal seam 1 is plotted in the forest moor zone, but the top sample of coal seam 1 shows an influence of transgressed sea water. Oil shale 1 is plotted in a transition zone from forest moor to open moor. This indicates an increased abundance of lower plants and algal derived organic matter in oil shale 1 relative to coal seam 1. The boundary faults controlled the sedimentation in Huangxian basin. When the faults ceased to move, the peat of coal seam 1 was formed. When the faults became active again and the basin began to sink, sea water flowed into the swamps at which time oil shale 1 was deposited.