Tracking climate fluctuations in the North China during the Carboniferous-Permian transition using chemical weathering indices

The Late Paleozoic Ice Age, as the longest-lasting icehouse of the Phanerozoic, includes multiple periods of climate warming and cooling. However, there is still no general consensus on the driving mechanisms of climate fluctuations during the Late Carboniferous-Early Permian transition. Here, we analyze the chemical weathering indices and estimated land surface temperatures of mudstone in the Late Carboniferous-Early Permian strata in the Ordos Basin, North China Craton. It also combines this data with published equivalent weathering data from other regions to track global weathering changes during this key period. Our results exhibit the chemical index of alteration decreased at 301, 299 and 296.5 Ma, suggesting three cooling intervals. These cooling intervals have also been identified and interpreted in the North China Block, Midland Basin, and Gondwana Basins. A less-pronounced cooling events at 301 Ma, while two severe cooling events occurred around 299 Ma and 296.5 Ma. The three cooling intervals played a key role in the Late Paleozoic Ice Age to its icehouse apex in the early Permian. The first (301 Ma) and second (299 Ma) cooling intervals could be caused by the continuous decline in atmospheric CO₂, resulting from the global weathering of worldwide mafic rocks and expansion of paleotropical forests. The third (296.5 Ma) cooling interval could be intensified by rapid chemical weathering of the basalt from the Skagerrak-Centered large igneous province, which rapidly consumed atmospheric CO₂, contributing to the icehouse apex in the early Permian. This study provides new evidence for climate fluctuations during the Carboniferous-Permian transition and offers a better understanding of the driving mechanisms behind these climate changes during the Late Paleozoic Ice Age.