Reasons for abnormal thermal evolution of source rocks in Upper Paleozoic, southern North China

The Upper Paleozoic is widely distributed in southern North China with thick source rock and high organic abundance, mainly Ⅱ₂-Ⅲ type. Multiple stages of deformation during Indosinian, Yan-shanian and Himalayan resulted in the differences in thermal evolution degree between source rocks, which was the key factor for petroleum resource evaluation and exploration target identification in southern North China. Based on thermal evolution characteristics of source rocks in the Upper Paleozoic of the study area, the reasons for abnormal thermal evolution were found out, mainly hypozoic thermal metamorphism. Crust uplift during Mesozoic resulted in the south and north division of thermal evolution of source rocks in the Upper Paleozoic. Magmatism ever since Mesozoic was the root cause for regional high-degree thermal evolution. Regional dynamometamorphism and gravitational sliding also helped thermal evolution. Industrial petroleum resources in the Upper Paleozoic are mainly found around the edge of high thermal evolution zone, such as Yichuan of Luoyang-Xiangcheng of Juling-Luyi-Shenqiu of Tanzhuang-Niqiuji-Yanji. They are the regions favorable for Upper Paleozoic petroleum exploration in southern North China.