Maximum paleotemperature of main Paleozoic argillutite in the Eastern Sichuan Basin

The thermal evolution process of argillutite is related to its paleotemperature history, and the final evolution degree is controlled by the maximum paleotemperature. We recovered the maximum paleotemperatures of main Paleozoic argillutite in the Eastern Sichuan Basin based on paleothermal indicators. These formations reached maximum paleotemperatures 80-90 million years before present. The maximum paleotemperature of the top surface of the upper Permian Longtan Formation is 150 similar to 220 degrees C and bottom surface is 160 similar to 230 degrees C. The maximum paleotemperature of the top surface of the lower Silurian Longmaxi Formation is 160 similar to 250 degrees C and the bottom surface of the upper Ordovician Wufeng Formation is 170 similar to 260 degrees C. The maximum paleotemperature of the top surface of the lower Cambrian Qiongzhusi Formation is 210 similar to 320 degrees C and bottom surface is 210 similar to 320 degrees C. The maximum paleotemperatures of these formations have similar distribution characteristics, exhibiting a high to low trend both to south and to north and the highest temperature appearing around Fuling-Fengdu with some high temperature areas near Dazhou-Kaijiang. The evolution processes of main Paleozoic argillutite in the Eastern Sichuan can be divided into different phases, and now is in the high to over mature stage. The Eastern Sichuan Basin experienced a high maximum paleotemperature, followed by rapid rise which is favorable for shale gas generation and accumulation.