Global perturbations of carbon cycle during the Triassic-Jurassic transition recorded in the mid-Panthalassa

To examine environmental changes in the biosphere during the Triassic-Jurassic transition, with a particular focus on the global carbon cycle related to Central Atlantic Magmatic Provinces (CAMP) volcanism in the mid-Panthalassa, we established stratigraphic delta C-13(org) variations using Rhaetian (Late Triassic) to Hettangian (Early Jurassic) shales interbedded within deep-sea cherts in the Katsuyama section in the Mino-Tanba belt, SW Japan. High-resolution record of Rhaetian to Hettangian delta C-13(org) values in the mid-Panthalassa contain three distinct negative carbon isotopic excursions (NCIEs) before and across the Triassic-Jurassic boundary (TJB): the Rhaetian NCIE1 and NCIE2 show a deviation of 5.0 parts per thousand from ca. -24.0 parts per thousand to ca. -29.0 parts per thousand, whereas NCIE3 across the TJB shows a 3.5 parts per thousand deviation from ca.- 23.5 parts per thousand to ca. -27.0 parts per thousand. Our newly obtained NCIEs in the deep mid-Panthalassa can be correlated with the 613Corg records in the shallow-marine Tethyan regions (i.e., precursor, initial, and main CIEs), suggesting that three NCIEs in the Tethys and mid-Panthalassa likely reflected the global perturbations of the carbon cycle. Three NCIEs before and across the TJB can be interpreted as the consequence of the multiple CAMP volcanic episodes; i.e., the release of thermogenic methane from organic-rich sediments by CAMP intrusive rocks for NCIE1 and large-scale volcanically derived carbon species for NCIE2 and NCIE3. In addition, progressive increase of atmospheric pCO(2) throughout three NCIEs was possibly attributed to accumulation of volcanically derived CO2 from multiple CAMP eruptions, which resulted in the development of ocean acidification across the TJB. On the other hand, in view of the oxic conditions in the deep mid-Panthalassa during three NCIEs, the development of coeval oceanic anoxiceuxinic conditions was restricted solely to shallow-marine regions. Therefore, ocean acidification together with localized shallow-marine anoxia acted as environmental stresses on the biosphere, which eventually resulted in the severe biotic crisis at the end of the Triassic. (C) 2018 Elsevier B.V. All rights reserved.