Hydrocarbon source rocks in sedimentary basins of continental margins in the Middle-Late Paleozoic

The second half of the Paleozoic was marked by amalgamation of large continental blocks. The collision between the Laurentia and Baltica continents in the Devonian culminated in the formation of Laurussia. This event was followed by accretion of the Siberian and Kazakhstan continental blocks after the closure of the Uralian marine basin in the terminal Carboniferous-initial Permian. These processes were responsible for the formation of the Pangea supercontinent at the end of the Permian Period. They were accompanied by climate changes reflected in the alternation of warming and cooling epochs. One of these cooling epochs was terminated by large-scale glaciation of Gondwana at the end of the Carboniferous Period. Nevertheless, the most significant process, which drastically changed the existing paleogeographic situation, was colonization of continents by plants and animals, and, thus, accumulation of coaliferous formations in them. The lacustrine and sea basins also accumulated humic and mixed humic/sapropel organic matter (OM) in addition to pure sapropelic sediments.