Increased aridity across the Permian-Triassic transition in the mid-latitude NE Pangea

The Dalongkou section in Xinjiang, Northwest China has preserved a continuous terrestrial Late Permian-Early Triassic sequence with well-studied information of biota evolution and isotopic excursion. In order to know the corresponding palaeoclimatic and palaeoenvironmental evolution in this critical transition, chemical weathering indexes (chemical index of alteration [CIA], plagioclase index of alteration [PIA], and chemical index of weathering (CIW)) are analysed in high resolution across the Permian-Triassic Boundary. Results show that the declining trend of the CIA, PIA, and CIW was related to the continuous decrease of the chemical weathering in the latest Permian. The climate in the mid-latitude NE Pangea was becoming increasingly arid in a generally greenhouse warm climate, causing widespread wildfire and turnover of the fauna and biota, coupled with the environmental deterioration expressed by the anomalies of carbon and mercury. Climatic conditions oscillated in the Early Triassic with possible intermittent rainfall and was likely affected by the strengthening of the megamonsoon. In the latest Permian-earliest Triassic, whether chemical weathering strengthened or weakened, as well as whether the climate was increasingly arid or humid, varied in the different places. The possible reasons inducing this need to be further explored.

Automated summary

The study indicates that the climate in the late Permian was continuously becoming drier, leading to a decrease in surface chemical weathering. The climatic conditions oscillated in the Early Triassic, possibly influenced by the megamonsoon.