## 1 Introduction  
The Hailar Basin, located in southwestern Hulunbuir, Inner Mongolia, is a Mesozoic-Cenozoic continental fault basin that developed on the Paleozoic Xingmeng Orogenic Belt. It is rich in petroleum, coal, and other resources. Significant oil and gas discoveries have been made in the Urxun, Beier, and Huhenuo sags in the southern part of the basin, with annual production exceeding 400,000 tons, making it an important area for oil and gas exploration in the Daqing Oilfield [1,2].  
Currently, hydrocarbon exploration in the Hailar Basin has primarily focused on the Cretaceous play. Previous studies have extensively investigated the geological structure, source rocks, reservoir distribution, hydrocarbon migration, and accumulation, leading to the identification of seven oil-bearing zones: Huhenuo, Suderte, Huodomoer, Beizhong, Surennuoer, Wudong, and Bayantala [2, 3, 4, 5, 6, 7, 8]. However, after more than 60 years of continuous exploration, the main oil-bearing formations in the Cretaceous have entered the mid-to-late development stage, with shallow, large-scale, easily discoverable structural oil reservoirs being almost fully explored. Consequently, exploration efforts are shifting from the shallow Cretaceous to the deeper Jurassic play.  
In recent years, oil stains and hydrocarbon shows have been observed in the Jurassic Wanbao Formation in the adjacent Tuquan Basin. In the Erlian Basin, 17 Jurassic wells have shown oil and gas indications, with two yielding low oil production [9]. Jurassic oil and gas exploration in the Hongqi Depression of the Hailar Basin has resulted in significant hydrocarbon shows in wells Hong D3, Hong 2, Hong 5, and Haishen 6, with industrial oil flows observed in well Hong 7. Additionally, well Hong 6 in the southern part of the sag produced low-yield oil from the Upper Jurassic Tamulangou Formation. Oil-source correlation studies indicate that hydrocarbons are derived from the Tamulangou Formation, forming a lower-generation, upper-reservoir hydrocarbon accumulation model [10]. Although previous studies have examined the structural characteristics, sequence stratigraphy, sedimentary systems, source rocks, and oil-source correlation in the Hongqi Depression [10, 11, 12, 13, 14], a systematic analysis of the geochemical characteristics and thermal evolution history of the Tamulangou Formation source rocks is still lacking, which constrains further exploration progress.  
Source rocks are fundamental to hydrocarbon accumulations. The evaluation of source rock geochemical characteristics and thermal evolution history is essential for hydrocarbon resource assessment and has been a crucial research focus in petroleum geology [15, 16, 17, 18, 19, 20, 21, 22]. This study systematically evaluates organic matter abundance, kerogen types, and maturity using organic geochemical methods [23, 24, 25, 26]. The EasyRo% method is applied to reconstruct the thermal evolution history of Jurassic source rocks in the Hongqi Depression [27, 28, 29], determining key parameters such as maximum geothermal gradient, peak paleotemperature, and hydrocarbon generation history. These findings provide important theoretical and practical implications for hydrocarbon exploration in the region.