Early–middle Permian drying in the North China Block induced by large igneous provinces

Abstract

The early–middle Permian records the Earth's last icehouse–greenhouse transition, providing insights into future climate changes in response to global warming in the modern icehouse world. However, the lack of continuous climatic records for this period hinders our understanding of the causes and effects of the climatic transition. Here we reconstruct the early–middle Permian climatic changes in the tropical North China Block (NCB), by zircon U-Pb dating and studies of palaeomagnetism and multiple environmental proxies in a fluvial–lacustrine succession to elucidate the climatic transition enigma. Dating constrains the age of the section to ~295–266 Ma. The chemical index of alteration (CIA) values show an oscillatory decreasing pattern over time, consistent with the variation of total organic carbon content and gradual upward diminishing of black mudstone, indicating long-term drying of the NCB from the early to middle Permian. The distinct oscillatory decrease in organic carbon isotope (δ 13 C org ) and CIA values during the time intervals of ~295–280 and ~270–266 Ma correspond to a series of large igneous province (LIP) activities, whereas a slighter decrease in δ 13 C org and CIA values correlates with weak LIP activity, indicating that LIPs played a dominant role in greenhouse-gas emissions and the resultant early–middle Permian warming. We also infer that the LIP-induced warming and associated Southern Hemisphere deglaciation shifted the Intertropical Convergence Zone southward, thereby leading to long-term drying in the tropical NCB. • A fluvial-lacustrine succession in the Ordos Basin is dated at ~295–264 Ma. • Long-term drying is indicated by decreasing chemical weathering. • Distinct δ 13 C decreases coincide with large igneous provinces (LIPs) activities. • The drying is causally related to the ITCZ shift driven by the LIPs-induced warming.