Paleoenvironment of the Upper Paleozoic marine-continental transitional shales and its implications for organic matter enrichment in the L-Block, eastern Ordos Basin, North China

After the successful exploration of marine shale gas, the marine-continental transitional shale gas has gained plenty of attention in China for its great resource potential. However, little work has been finished regarding on the paleoenvironment and organic matter accumulation within shales. Based on element geochemistry, it is concluded that the Upper Paleozoic strata underwent a transition from marine to continental environment but the climate, sedimentary facies, and redox condition did not coevolve synchronously. The organic matter enrichment is controlled by redox condition, not the climate and the Taiyuan Formation, with the highest total organic carbon content, is also favorable for transitional shale gas exploration in the L-Block, eastern Ordos Basin.