PROVENANCE OF LATE PERMIAN VOLCANOGENIC SEDIMENTS AT PENGLAITAN, SOUTH CHINA

At the end of the Permian period, ~96% of all living organisms went extinct. Today, the cause for this extinction is still debated. The most widely accepted theory revolves around the Siberian Traps; a large igneous province in central Russia. At 251.9 Ma, this was a highly active volcanic province that is thought to have contributed to the mass extinction, but whether the eruptions were stressing marine environments prior to the final extinction remains unknown. The Penglaitan section, in the Guangxi Autonomous Region of Southern China, is one of few places that records continuous sedimentation leading up to the end-Permian and into the Triassic. Late Permian (Wuchiapingian and earliest Changhsingian) strata at Penglaitan contain beds with distinguishable volcanic influence, showing evidence ranging from vitric tuff to coarse volcanoclastic sandstones containing euhedral plagioclase grains. These layers were also organic-rich and contained many ammonoid impressions. Geochemical data suggests that much of this organic matter is derived from terrestrial plants that were washed into the Nanpanjiang Basin. These layers were formed at a time when the Siberian Traps were active, and it is possible that these flood basalt eruptions could explain the unusual volcanic characteristics seen in the samples. However, the South China microcontinent was also experiencing subduction along its southern margin, leading to arc volcanism during this time period. Rocks that form from flood eruptions like the Siberian Traps possess different geochemical characteristics than rocks formed from volcanic arcs, and many of these geochemical signatures can be traced even into mature sediments produced from the original volcanic source. The goal of this project is to understand the origin of these volcanically influenced sediments using geochemical techniques. X-ray fluorescence spectroscopy will be used to determine the elemental composition of the samples. A subset will be analyzed using acid digestion, to generate data on trace and rare earth element abundances. Using these data, we will determine whether a detectable Siberian Traps signal was impacting shallow marine environments in South China by the early Changhsingian.