Tectonic–thermal evolution since the Mesozoic in the Suhongtu Depression, Yingen–Ejina Basin: Constraints from Apatite fission track and vitrinite reflectance

The Yingen–Ejina Basin (YEB) located in the western part of the North China Plate is a significant area for petroleum exploration. During the Early Cretaceous, the YEB witnessed the extensive development of source rocks. However, the subsequent tectonic evolution and multi‐stage thermal history of these source rocks have posed challenges to oil and gas exploration in the basin. This study focuses on the Mesozoic and Cenozoic tectonic evolution of the YEB, utilizing Apatite fission track (AFT) and vitrinite reflectance ( Ro ) data of samples from Well BC‐1 in the Suhongtu Depression, northern YEB. The central ages of six AFT samples ranged from 28 ± 2 to 49 ± 3 Ma with corresponding track lengths between 10.8 ± 1.9 and 12.3 ± 1.5 μm. Combining with the study of Ro and thermal history simulation, the thermal history of the YEB is summarized as follows: In the late Early Cretaceous, the study area experienced tectonic elevation, as evidenced by the discontinuous change in Ro values along the vertical column. Towards the end of the Late Cretaceous, there was a subsidence in the study area. The Ro data indicate that the Early Cretaceous source rocks, although experiencing several tectonic uplifts, had remained within the hydrocarbon generation temperature range, and reached the maximum thermal uplifts before the end of the Late Cretaceous. Therefore, hydrocarbon generation from early Cretaceous source rocks is an important exploration target in the study area and will be the focus of oil and gas exploration in the future.