## 4 Tectonic Evolution and Sedimentary Filling of the Basin
### Hydrocarbon Source Rock Conditions  
The Triassic Basin is primarily characterized by two dominant hydrocarbon source rocks: Upper Devonian dark mudstone and Lower Silurian graptolite shale [67]. Additionally, there is a secondary hydrocarbon source rock from Ordovician dark mudstone. These three hydrocarbon source rocks are widely and consistently distributed throughout the basin (Figure 8). The Ordovician dark mudstone in the basin primarily consists of types I-II organic matter with a relatively low total organic carbon (TOC) content, categorizing it as a medium-grade hydrocarbon source rock. In contrast, the Upper Devonian hot shale and the Lower Silurian Tanezzutf graptolitic hot shale exhibit a more consistent distribution. The Tanezzutf hot shale from the Lower Silurian is a principal hydrocarbon source rock in Algeria. Remarkably, 80-90% of the hydrocarbons in the North African Paleozoic Era originate from this formation [70]. This hot shale, deposited after the Late Ordovician ice age, is black shale, resulting from the most extensive marine transgression. It represents a deep shelf anoxic sedimentation characterized by dark, highly radioactive graptolite mudstone, globally recognized as a premium hydrocarbon source rock (Table 1). This hydrocarbon source  
Figure 8: Lithological and electrical characteristics of hydrocarbon source rocks in the North African Triassic Basin (Modified from [68] [PERSON], 2019, and [69] [PERSON], 2020). (**a**). North Africa single well composite histogram. (**b**) Silurian hydrocarbon source rock core. rock can reach a thickness of up to 100 m, with an average thickness of 50 m, spanning an area exceeding 20,000 km\({}^{2}\). The organic matter in this rock is primarily of types I-II 1 kerogen, with a TOC ranging from 1% to 17%, peaking at 26.2%. Different structural units exhibit variations in organic richness. For instance, the TOC in the Oued Mya Basin ranges from 3% to 10%, while in the Hassi Messaoud uplift, it varies between 1% and 17%, with the highest concentration in the Tidikelt dome reaching 20%. The Lower Silurian formation is rich in organic content, highly evolved, and has a significant hydrocarbon generation potential, typically exceeding 60 kg/t, making it an excellent-to-superior hydrocarbon source rock. Influenced by tectonic movements, the maturity of the hydrocarbon source rock, and hydrocarbon expulsion efficiency, the TOC content gradually increases from the southern to the northern parts of the basin. However, some of the Lower Silurian hydrocarbon source rocks might have been eroded in uplifted areas. Previous studies have indicated that the effective hydrocarbon generation and expulsion from the Lower Silurian hydrocarbon source rocks in the Hassi Messaoud Uplift began in the Late Jurassic, peaking in the Late Cretaceous to Neogene. In terms of regional organic maturity, the vitrinite reflectance (Ro) in the Timimum Basin ranges from 1.0% to 4.0%. In the Oued Mya Basin, the Ro varies between 0.5% and 1.3%, with the basin's center reaching up to 1.5%. The Hassi Messaoud Uplift has an Ro of 0.8% to 1.1%. These parameters collectively indicate that the organic matter in the Lower Silurian hydrocarbon source rock has matured and is in a phase of extensive hydrocarbon generation. During the Early Silurian period, the lithological profile of the Longmaxi Formation in the Sichuan Basin of South China is characterized by deep-water shelf deposits in the lower part, with a higher content of gratpolites, predominantly dominated by Climacogratus [71]. Pyrite is locally enriched in thin layers and bands. The upper part is characterized by shallow-water shelf deposits with fewer gratpolites, mainly consisting of single gratpolites. Pyrite is often enriched in nodules and concretions. In the deep water shelf deposition zone, the thickness of organic-rich mud shale generally ranges from 40 to 120 m. For instance, the thickness reaches 80-120 m in the area of Shizhu Qiliao-Jiaoshiba-Dingshan-Changing Shuanghe-Leibo Bajiaotan.