4:45 PM - 5:00 PM
[BCG09-18] Global perturbations of carbon cycle in the mid-Panthalassa during the Triassic-Jurassic transition
Keywords:mass extinction, Central Atlantic Magmatic Provinces (CAMP), deep-sea oxygenation, organic carbon isotopes, bedded cherts, Japan
A high-resolution Rhaetian to Hettangian δ13Corg values in the mid-Panthalassa contain three distinct negative carbon isotopic excursions (NCIEs) before and across the T-JB; the Rhaetian NCIE1 and NCIE2 occurred for 5‰ from ca. -24.0‰ to -29.0‰, whereas the NCIE3 across the T-JB occurred for 3.5‰ from ca. -23.5‰ to -27.0‰. The newly observed NCIEs in the deep mid-Panthalassa can be correlated with the δ13Corg records in the shallow-marine Tethyan regions; i.e., St Audrie’s (England), Tiefengraben (Austria) and Čanj (Montenegro). This suggests that three NCIEs in the mid-Panthalassa reflect the global perturbations rather than local phenomena. Especially, the NCIE2 and NCIE3 occurred under high atmospheric CO2 levels, whereas atmospheric CO2 concentrations during the NCIE1 was around background values. This pCO2 level during the NCIE1 might be attributed to consumption of atmospheric CO2 by intensified weathering of the CAMP basaltic rocks. We thus consider that the NCIEs in the mid-Panthalassa before and across the T-JB were attributed to the volcanically CO2 outgassing from multiple emplacements of the CAMP volcanism. In addition, the high atmospheric CO2 level associated with the CAMP volcanism across the T-JB could promote the continental weathering in the shallow-marine regions, which might have accelerated burial of organic matter. This process likely resulted in deep-sea oxygenation in the mid-Panthalassa across the T-JB. From the above, the multiple emplacements of the CAMP volcanism during the Triassic-Jurassic transition had played a significant role for perturbations in carbon cycle in addition to the redox condition in the mid-Panthalassa.