Intensified chemical weathering during the Permian-Triassic transition recorded in terrestrial and marine successions

摘要

Global warming is inferred to have been one of the main causes of the Permian-Triassic (P-Tr) boundary mass extinction. Although a strong temperature rise in tropical sea-surface temperatures during the latest Permian has been documented, coeval climate changes in terrestrial sections are less well-known. Here, we analyzed multiple weathering indexes (including CIA, CIW, and PIA) for two terrestrial sections in North China (Shichuanhe and Yima), all of which show a major excursion toward higher values (greater weathering intensity) around the end Permian plant extinction (EPPE). At Shichuanhe, the CIA (chemical index of alteration) increases from 70 to 75 over the interval of 11-36 m, which straddles the EPPE at 33 m, and then decreases from 75 to 71 in the overlying strata. At Yima, CIA increases from 63 to 79 over the interval of 57-68 m, extending up to the EPPE at 68 m, and then gradually decreases from 78 to 72 in the overlying strata. These results imply a strong warming event coupled with intense chemical weathering in soil environments leading up to the end-Permian plant extinction. The decline in CIA values following the EPPE may reflect loss of weathered soils through physical erosion rather than climatic cooling. Estimation of atmospheric temperatures from the CIA data indicate rapid rises at Shichuanhe (from similar to 11.6 degrees C to 16.5 degrees C) and Yima (from 9.3 degrees C to 18.4 degrees C) during the end-Permian crisis. The findings in this study are consistent with the hypothesis that a sharp temperature rise caused the extinction of terrestrial organisms during the end-Permian crisis.