NEOPROTEROZOIC OCEAN CHEMISTRY: STABLE ISOTOPE EVIDENCE FROM CHINA

Abundant geological evidence indicates that glacial deposits of Neoproterozoic age (1000-544 Ma) occur globally and repeatedly and the most extensive of these Neoproterozoic glacial deposits formed during the Marinoan glaciation. A great number of debates about Neoproterozoic environmental changes center on C-isotopic data from “cap carbonate” beds that are usually less than 10m thick. However, with some exceptions, much less geochemical analyses have been done on those postglacial sedimentary rocks following the deposition of cap carbonates.

Here I will report stable isotope data from sedimentary rocks of the Doushantuo Formation in south China, which consists mostly of carbonates and black shales, as well as phosphate deposits. Well-reconstructed different sedimentary facies along paleoenvironmental gradient from the carbonate platform to deep basinal facies are perfectly preserved in the region. The isotopic measurements integrated with sedimentary facies allow us to investigate the spatial structure of the postglacial ocean. I will also discuss the relationship between the change of Neoproterozoic ocean chemistry and early animal evolution.