T194 Permian-Triassic Biotic Crisis: New Insights through Integrative Studies of Earth, Ocean, and Atmosphere (Posters)

Tuesday, 6 November 2018
9:00 AM - 6:30 PM
Halls J-K

EPISODES OF PERTURBATIONS OF CARBON AND NITROGEN CYCLES COUPLED WITH PERMO-TRIASSIC TERRESTRIAL MASS EXTINCTION IN NE PANGEA, BOGDA MOUNTAINS, NW CHINA

Paper number: T194-11
Program: Technical Sessions
Time: 9:00 AM – 6:30 PM

Authors

  • Xin Zhan Presenting Author
    Missouri University of Science and Technology, Rolla, MO
  • Wan Yang
    Missouri University of Science and Technology, Rolla, MO
  • Yujiao Zhang
    Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou

Abstract

The timing, pattern, and causes of marine Permo-Triassic mass extinction (PTME) are well documented, but those of terrestrial PTME are poorly understood due to poor chrono- and biostratigraphic, geochemical, and geological constraints. Organic carbon (δ13Corg) and nitrogen (δ15Norg) isotopic compositions of kerogen were analyzed in in five high-resolution terrestrial sections across northern and southern Bogda Mountains over 90 km. The results show that prominent negative excursions of δ13Corg, from ~-23 to ~-31‰, occurred ~30 m above the last coal seam in the vicinity of Permo-Triassic boundary (PTB) in the five sections, concurrent with major positive shifts of δ15Norg from ~+5 to ~+7‰. Constrained by two U/Pb zircon ages of 250.32 ± 0.08 Ma at southern Taodonggou and 254.11 ± 0.05 Ma at northern Tarlong in the study area, those negative δ13Corg excursions in northwestern China can be correlated to the δ13Corg depletion near the PTB at terrestrial Chahe and marine Meishan sections in Southern China and, indirectly, inorganic δ13C records across PTB at marine Yunnan section in southern China. The δ13Corg chemostratigraphy locates a potential terrestrial PTB in northwestern China. Episodes of positive δ15Norg excursions synchronize with the negative δ13Corg excursions, suggesting intermittent CO2 input in carbon cycle and enhanced nitrification and denitrification in intermittent aerobic nitrogen cycle during PTME. Abundant volcanic ash layers present right above the potential PTB, suggesting massive volcanic eruptions during the mass extinction interval. The coincidence of perturbation of carbon and nitrogen cycles, biotic extinction event, and volcanic eruptions suggest that PTME may result from CO2 emissions from magma-coal interactions during flood magmatism in Siberian Trap.

Geological Society of America Abstracts with Programs. Vol. 50, No. 6

doi: 10.1130/abs/2018AM-322677

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