Integrated Sr isotope variations and global environmental changes through the Late Permian to early Late Triassic

摘要

New Sr-87/Sr-86 data based on 127 well-preserved and well-dated conodont samples from South China were measured using a new technique (LA-MC-ICPMS) based on single conodont albid crown analysis. These reveal a spectacular climb in seawater Sr-87/Sr-86 ratios during the Early Triassic that was the most rapid of the Phanerozoic. The rapid increase began in Bed 25 of the Meishan section (GSSP of the Permian-Triassic boundary, PTB), and coincided closely with the latest Permian extinction. Modeling results indicate that the accelerated rise of Sr-87/Sr-86 ratios can be ascribed to a rapid increase (>2.8x) of riverine flux of Sr caused by intensified weathering. This phenomenon could in turn be related to an intensification of warming-driven runoff and vegetation die-off. Continued rise of Sr-87/Sr-86 ratios in the Early Triassic indicates that continental weathering rates were enhanced >1.9 times compared to those of the Late Permian. Continental weathering rates began to decline in the middle-late Spathian, which may have played a role in the decrease of oceanic anoxia and recovery of marine benthos. The Sr-87/Sr-86 values decline gradually into the Middle Triassic to an equilibrium values around 1.2 times those of the Late Permian level, suggesting that vegetation coverage did not attain pre-extinction levels thereby allowing higher runoff. (C) 2015 Elsevier B.V. All rights reserved.