A conodont-based revision of the 87Sr/86Sr seawater curve across the Permian-Triassic boundary

Abstract

Based on analyses of 565 conodonts from Meishan, Liangfengya, and Daijiagou (South China), and Abadeh (central Iran), we propose a revision of the seawater 87Sr/86Sr curve for the time period spanning 200kyr prior to the Permian-Triassic boundary (PTB) to 330kyr after the PTB. With carefully designed sample cleaning, conodonts faithfully record seawater 87Sr/86Sr. Seawater 87Sr/86Sr was 0.707030±10,200kyr prior to the PTB, rose to 0.707070±10 approximately 39kyr prior to the PTB (at the marine extinction horizon, the top of Bed 24e at Meishan), to 0.707080±10 at the PTB, and to 0.707120±20 at 330kyr after the PTB. The rate of change of seawater 87Sr/86Sr was 0.0000185/Myr from the Capitanian minimum to ~100kyr before the PTB, and was 0.00020±7.5/Myr between ~100kyr before and 330kyr after the PTB. Over 6Myr, this rate of change would result in a maximum 87Sr/86Sr of ~0.70825 at the end of the Early Triassic, compared with a model value of ~0.7080. The Sr data are consistent with the interpretation that the rise in marine 87Sr/86Sr was due primarily to an increase in the continental weathering and erosional flux, and that soil-binding vegetation was not re-established during most of the Early Triassic. The rapid rise in seawater 87Sr/86Sr began at least 30kyr prior to the marine extinction at Meishan, indicating that the terrestrial extinction preceded that in the oceans.