PALEOENVIRONMENTAL CHANGES PRIOR TO THE PERMIAN-TRIASSIC TRANSITION - EVIDENCE FROM THE MANDAKPAL VALLEY SECTION, KASHMIR, INDIA

The Permian-Triassic Boundary marks a global mass extinction event that occurred around 250 mya. The marine record of this time reflects a global environmental crisis linked to the loss of close to 96% of marine species. Drivers of the changes in ocean conditions preceding the main extinction event are numerous and interdependent. Our understanding of ocean conditions and the rate and cause of changes in oxygenation, circulation, and acidification are largely based on the geochemistry of Permian marine sections deposited in the paleo-equitorial Tethys Ocean basin. Without a more global comparative record it is impossible to isolate the truly global environmental conditions from those of local significance.

Here we integrate data from the higher latitudes of the Neo-Tethys Ocean to present a richer understanding of ocean conditions at the time of this extinction. We collected samples (n=45) along a thirty-four meter transsect in the Mandakpal Valley of the Himalayan mountain range in Kashmir, India. This section extends through the D member of the Zewan Formation to the Lowermost E1 member of Khunamuh Formation. The lithology of this section is alternating shale and limestone deposits that cover the Uppermost Permian across the boundary into the Lowermost Triassic. We chemostratigraphically aligned this section to the well-studied Guryul Ravine section (Kashmir). The Mandakpal Valley section, like the Guryul Ravine section, records episodic anoxia/euxinia as well as evidence of changes in sedimentation rate. With the chemostratigraphic record of these two sections in Kashmir compared to southern Neo-Tethys sections in Spiti Valley (Himachal Pradesh, India) and the well-studied Paleo-Tethys sections such as Meishan, we show that this region of the Neo-Tethys was typified by dysoxia with increasing frequency of anoxic/euzinic intervals approaching the end-Permian.