Composition Peculiarities of the Upper Devonian Coaly Rocks (The Sula River Section, North Timan)

A detailed coal-petrographic and mineralogical-geochemical study of humic coals and coaly rocks in the Sargaev deposits of the Upper Devonian of the Northern Timan (Sula River), which is an example of the burial of the most ancient coal-forming plants, has been carried out. The following types of organic rocks are identified in the section: “jet-like” coal, liptobiolitic silty-clayey coal, and silty-clayey-coaly mixtolites. The studied coals and coaly rocks are composed of humic organic components, represented by vitrinite and liptinite macerals, the inertinite group is of subordinate importance. Vitrinite macerals include gelinite, collotelinite, and telinite (xylenite), liptinite macerals include sporinite, cutinite, liptodetrinite, bituminite, alginite, and a resinous substance, and inertinite macerals include inertodetrinite, semifusinite, fusinite, and funginite. The level of organic matter maturity according to the vitrinite reflectance RV = 0.45–0.55%, corresponds to the transition from proto- to meso-catagenesis (gradations PC3–MС1). The mineral component of mixtolites and high-ash coals consists of kaolinite, chlorite/smectite (with a predominance of the chlorite component) and quartz.