XIE Shucheng and YIN Hongfu, a professor and an academician with China University of Geosciences, in collaboration with British scholars, have concluded from their study of molecular fossils unearthed from the Permo/Triassic (P/Tr) boundary at Meishan in South China that faunal mass extinctions in Earth history have experienced at least twice biotic crisis. Prof, XIE and others separated microbialites from marine food chain fossils, and calculated time variations using these biomarkers. They concluded that there occurred at least twice drastic microbial changes across the P/Tr boundary. For example, the biomarkers present two maximum values at 26th and 29th levels of the Meishan section, which indicates two multiplication peaks for the bacteria. In the meantime, researchers discovered two biotic extinction peaks for invertebrates at 25th and 28th-29th levels, which occurs right before the two multiplication peaks, showing a well connected coupling.
XIE points out that each biotic extinction is followed with a microbial multiplication peak, which reflects microbial responses to the catastrophic events that caused the extinction and initiated ecosystem changes. Their findings show that the catastrophic events occurred 250 million years ago is multi-phased in nature. Major causes of the events come from the inner earth, rather than the outer one. The finding is published in the journal Nature. |
