Source rocks in sedimentary basins of continental margins in the early paleozoic

During the Paleozoic, epochs with the relatively cold climate alternated with epochs marked by significant warming. Moreover, cooling epochs were characterized by the substantial sea level fall, while warming was accompanied by its rapid rise. In many basins located at margins of Laurentia, Baltica, and the North China continental block, such an alternation is reflected in the structure of sedimentary sequences and the lateral/vertical distribution of reservoirs, confining beds, and source rocks. Despite the fact that sediments with high concentrations of sapropelic OM accumulated in different periods, their distribution areas on continents and their margins became highly reduced during cold epochs, when these sediments filled mostly rift troughs and foreland basins. After the colonization of land by higher plant communities in the Carboniferous and Permian sediments deposited during cold epochs, the humic material became an important constituent of OM in the source rock sequences.