GSA Annual Meeting in Denver, Colorado, USA - 2016

Paper No. 76-14
Presentation Time: 9:00 AM-5:30 PM


STEBBINS, Alan G., School for the Environment, University of Massachusetts Boston, 100 Morrissey BLVD, Boston, MA 02125, WILLIAMS, Jeremy C., Department of Geology, Kent State University, 228 McGilvrey Hall, Kent, OH 44240, BROOKFIELD, Michael, School for the Environment, University of Massachusetts Boston, 100 Morrissey Boulevard, Boston, MA 02125 and HANNIGAN, Robyn, School for the Environment, University of Massachusetts, 100 Morrissey Boulevard, Boston, MA 02125,

The end-Permian mass extinction was coincident with widespread oceanic anoxia. The timing of the onset of the anoxic event likely varied within and between ocean basins. In this study, we seek to refine oxygenation conditions of an understudied region of the Neo-Tethys (Spiti Valley, Himachal Pradesh, India) through the measurement of pyrite framboid size distributions. We present pyrite framboid size distributions for three Late Permian sections (Mud, Lingti, Attargoo). Each section consists of black to silty shales from the Late Permian Gungri Formation which is uncomformably overlain by a 5-10 cm ferruginous layer (FL). The FL is thought to be a gap in sedimentation and broadly marks the transition from the Late Permian shales to the Early Triassic limestone consequently engulfing the Permian-Triassic boundary for these sections. The diameter of individual pyrite framboids were measured using a Scanning Electron Microscope in backscatter electron mode. Results suggest that, during the Wuchiapingian to early Changhsingian substages of the Late Permian, the waters of the southern Neo-Tethys experienced multiple euxinic intervals well prior to the end-Permian mass extinction that interrupted a longer term dysoxic trend. Results will be compared to previously published datasets both within the Neo-Tethys as well as other ocean basins.