## 6 Conclusions  
1. The dark mudstone of the Jurassic Tamulangou Formation in the Hongqi Depression has a thickness ranging from 50 to 200 m. The total organic carbon (TOC) content varies between an average of 0.14% to 2.91%. The chloroform bitumen \"A\" content averages 0.168%, and the hydrocarbon generation potential (S\({}_{1}\) + S\({}_{2}\)) averages between 0.13 to 3.71 mg/g. The kerogen carbon isotope values range from \(-\)27.52% to \(-\)21.37%. The organic matter type is mainly Type II and Type III, with the source material coming from both low-level aquatic organisms like algae and higher terrestrial plants. The vitrinite reflectance (Ro) averages between 0.71% and 1.36%. Overall, the source rocks have entered the mature oil generation stage, and the source rock is evaluated as being of medium quality.
2. The thermal history simulation results show that the Hongqi Depression's Tamulangou Formation source rock has undergone two main thermal evolution stages since its deposition: a rapid warming stage during the Late Jurassic to Early Cretaceous and a slow cooling stage from the Late Cretaceous to the present. The thermal evolution  
Figure 11: Sedimentation rate diagram of the Hongqi Depression. (**a**) Sedimentation rate diagram of H6 in the Hongqi Depression; (**b**) Sedimentation rate diagram of H7 in the Hongqi Depression.  
history varies across different locations. In the southern part of the sag, the thermal evolution is more advanced. The Jurassic Tamulangou Formation source rock reached the hydrocarbon generation threshold at 138 Ma, peaked around 119 Ma with Ro reaching 1.0%, and the maximum paleo-temperature exceeded 140 \({}^{\circ}\)C. It is currently in the high-maturity oil generation stage. In the central part of the sag, the thermal evolution is less advanced. The source rock reached the hydrocarbon generation threshold at 128 Ma, entered the medium-maturity stage around 74 Ma, and has remained in this stage ever since.
3. During the Late Jurassic to Early Cretaceous, the Hailar Basin was in a stable rifting stage, characterized by significant and rapid subsidence and sedimentation. The maximum sedimentation rate reached 340 m/Ma, accompanied by intense volcanic activity, which created a high geothermal field. The geothermal gradient reached 40-65 \({}^{\circ}\)C/km, with paleo-temperatures exceeding 140 \({}^{\circ}\)C, and the warming rate was 1.38-2.02 \({}^{\circ}\)C/Ma. The source rock reached its maximum thermal evolution stage, which is consistent with the relatively high thermal background during the late Early Cretaceous in northern China basins. Afterward, the basin uplifted and cooled, with a decrease in subsidence and a gradual reduction in the formation temperature. The temperature evolution showed a pattern of first increasing and then decreasing.  
Data collection and analysis, W.J.; data analysis, discussion, and result analysis, J.C., H.T. and Z.R.; article writing, J.C.; cartography and translation, H.T., H.S. and W.G. All authors have read and agreed to the published version of the manuscript.  
This study was supported by the General Program of the National Natural Science Foundation of China (No. 41772121) and the Key Program of the National Natural Science Foundation of China (No. 41630312).  
Not applicable.  
All data related to this manuscript have been fully submitted to and are available from the editorial board.  
Author [PERSON] was employed by the company China National Petroleum Corporation. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.