oa Tasmanites Blooms During Early Permian Artinskian Deglaciation

This study reports the first discovery of Tasmanite oil shales in northern Pangea, specifically in the Lucaogou Formation of the Junggar Basin, China, deposited during the Artinskian (ca. 290 Ma). The organic petrological features of Tasmanites are clearly visible, including thick-walled disks with tubes and radially arranged channels. These shales have markedly elevated C28/C29 steranes and tricyclic terpanes/hopanes ratios. Based on inorganic geochemical data, the salinity of the paleo-lake during deposition of the Tasmanite oil shale interval decreased abruptly from saline to brackish–freshwater. In addition, the pH changed from alkaline to nearly neutral, while the redox environment changed from anoxic to suboxic. Enhanced continental chemical weathering and the change in salinity of the paleo-lake occurred at the same time as global warming and large-scale glacier melting during the Artinskian, which promoted the habitat of the low-salinity tolerant Tasmanites. Our results provide new geological evidence for another occurrence of early Permian Tasmanite oil shales, indicating that Tasmanites flourishs and the associated oil shales may have been widely deposited at the end of the LPIA. The flourishment of Tasmanites archives biotic–environmental co-evolution.