T169 Chemostratigraphy: Physical and Temporal Applications

Tuesday, 24 September 2019
8:00 AM - 12:00 PM
Room 224B, North Building

PERMIAN-TRIASSIC GLOBAL MARINE AND TERRESTRIAL CARBON CYCLE RECORDS FROM THE FINNMARK PLATFORM IN NORWAY

Paper number: T169-7
Program: Technical Sessions
Time: 9:35 AM – 9:50 AM

Authors

Abstract

The end-Permian mass extinction event (EPE;ca. 251.9 Ma) is characterized by a large negative carbon isotope excursion (CIE) in both marine and terrestrial realm. The magnitude of the CIE, however, is debated due to the stratigraphic condensation of many marine sites and changes in the environments of terrestrial sites. Here, we report a high-resolution compound specific carbon isotope records of organic matter that are thermally immature to early mature from two drill cores deposited in shallow marine environment offshore Finnmark, Norway. We use statistical methods of correlation coefficient and TimeOpt to estimate the optimal sedimentation rate and to establish a high-resolution astrochronology at the Finnmark Platform, which allows for testing the global carbon isotope pattern. The new isotopic records suggest that marine algae (C17and C19n-alkanes) likely represent true marine CIE because no evidence of regional ocean anoxia or changes in microbial community is found in the study site, suggesting the -6‰ CIE is of global significance. On the other hand, the terrestrial (C27 and C29 n-alkanes) CIE is distorted due to changes in climate pattern and vegetation type across the Permian-Triassic transition. The rapid marine CIE (~ -6‰) occurred less than 13,000 years and remains at values ~2‰ lower than the pre-CIE condition, implying that despite the increased continental weathering and organic carbon burial rate, the global carbon cycle regime is fundamentally altered. To interpret a -6‰ global CIE, we run a global carbon cycle model cGENIE (carbon-Grid Enabled Integrated Earth system model) to infer changes in atmospheric pCO2and ocean carbonate chemistry. We find that the pCO2increased by 3.5 folds across the Permian-Triassic transition, resulting in more than 0.5 unit pH decrease and more than 5 ℃global surface ocean temperature rise, consistent with proxy evidence. We suggest the Siberian Traps volcanisms and the associated contact metamorphism is likely the trigger of the largest mass extinction event in the Earth history.

Geological Society of America Abstracts with Programs. Vol. 51, No. 5

doi: 10.1130/abs/2019AM-334028

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