PROVENANCE OF VOLCANOGENIC SEDIMENTS IN WUCHIAPINGIAN AND EARLIEST CHANGHSINGIAN STRATA AT PENGLAITAN

The Late Permian corresponds with two major environmental crises: the Guadalupian-Lopingian boundary, associated with the emplacement of the Emeishan Traps, and the end-Permian mass extinction, corresponding with emplacement of the Siberian Traps. Whether these expansive volcanic provinces contributed to environmental stress in marine environments between the two major extinction pulses, in the Late Permian prior to the end-Permian extinction, remains to be explored. The Penglaitan section, in the Guangxi Autonomous Region of southern China, is one of few places on earth that records continuous sedimentation from the Middle Permian through the Early Triassic, with high sedimentation rates and no major unconformities. In this study, we measured major element chemistry, trace elements, and REEs from Late Permian (Wuchiapingian and earliest Changhsingian) strata from the Penglaitan northern bank section. This succession contains numerous beds with distinguishable volcanic influence, ranging from vitric tuffs to coarse volcanoclastic sandstones containing euhedral plagioclase grains. Most of these volcanoclastic deposits reflect arc volcanism associated with subduction along the southern margin of the South China microcontinent. However, some samples contain REEs signatures and trace element ratios characteristic of undifferentiated intra-plate volcanism, and may be associated with large igneous eruptions. These samples occur in an interval that is notably organic-rich, and contains many ammonoid impressions. Organic geochemical data suggest that much of this organic material is derived from terrestrial plants, and it is possible that flood basalt eruptions could have led to rapid fluxes of terrestrial organic into the Nanpanjiang Basin.