Early Triassic carbon isotope excursions from South China: Proxies for devastation and restoration of marine ecosystems following the end-Permian mass extinction

Abstract

Early Triassic carbon isotopes are measured based on 1422 carbonate bulk samples from 10 Lower Triassic sections in different palaeogeographic settings in South China. Early Triassic fluctuation of δ 13C is used as a proxy for environmental change to discuss the devastation and restoration of marine ecosystems following the biggest Phanerozoic mass extinction at the end of the Permian. Early Triassic δ13C profiles derived from various depositional settings in South China yield comparable excursion patterns. A dramatic negative shift of δ13C across the Permian/Triassic boundary is followed by a moderate increase in δ 13C values throughout the Induan. A positive δ 13C anomaly occurs near the Induan/Olenekian boundary, followed by a Smithian interval of lower δ13 C values. A distinct positive shift in δ13 C coincides with the Smithian/Spathian boundary, and is followed by a high Spathian plateau of δ13C values. Thus the distinct δ13C anomalies coincide well with key stratigraphic boundaries. Early Triassic intervals of low δ13C values correspond to a decline in benthic generic diversity in South China and intervals of high δ13C values are coupled with an increase in biodiversity. The Early Triassic fluctuations of δ13C profiles are good proxies for perturbations of ecologic environments, indicating multiple phases of devastation-restoration of marine ecosystems punctuated by several unexpected extraneous events such as volcanic activity. The initial restoration of marine ecosystems may have occurred earlier in the Induan and the ecosystems were subsequently destroyed during the Smithian. Biotic and environmental recoveries occurred at the Spathian, while thee ecosystems eventually returned to normal levels in the early Middle Triassic. Copyright © 2007 John Wiley & Sons, Ltd.