ACCOUNTING FOR VARIATIONS OF DELTA-13-C ISOTOPIC RECORD AT THE LINGTI PERMIAN-TRIASSIC SECTION

The Permian-Triassic (PT) extinction is considered the largest extinction in Earth's history (~250 mya). The PT section that we studied, Lingti, is currently located in Spiti Valley, Himichal Pradesh, India. This section was deposited in the Neo-Tethys Ocean and records deposition in the late Permian and early Triassic. Lingti's stratigraphy consists of the upper Permian Gungri Formation (black shale) which is capped, unconformably, by a ferruginous layer that marks the PT boundary. Unconformably overlying the ferruginous layer is a lower Triassic non-calcareous microbreccia of the Mikin Formation. We used an Elemental Analyzer (EA) coupled with an Isotopic Ratio Mass Spectrometer (IRMS) to measure carbon and nitrogen weight percentages as well as carbon isotopic ratios. Major and trace element concentrations were measured by Energy Dispersion X-ray Fluorescence (ED-XRF). The stratigraphic trends in δ¹³ C, major, and trace elements reveal changes in depositional conditions and, potentially, primary production prior to the main extinction event. The Lingti section records a series of δ¹³C depletions occurring well before the boundary which coincide with fluctuations in Mn/Al, Mn/Fe, Fe/Al, V/V+Ni as well as changes in organic carbon and nitrogen. Juxtaposing Lingti against the Global Stratigraphic Section and Point (GSSP) at Meishan (China), we conclude that the fluctuations preserved in the geochemical record at Lingti are the result of major environmental disturbances prior to the main extinction.