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This paper discusses the maturity of source rocks of the Senegal basin through basin simulation, so as to get a better understanding of oil-source correlation. Based on the analysis of pyrolysis chromatography and total organic carbon (TOC) data of core samples taken from 11 wells, the model of Cenomanian-Turonian marine sediment- organic facies was established, and the genetic mechanism of high-quality source rocks was clarified. The results show that source rocks in the Senegal Basin may occur in the Aptian-Albian of Lower Cretaceous and Cenomanian-Turonian of Upper Cretaceous. One is hybrid organic facies in the shallow carbonate platforms in the shelf area and is characterized by moderate to high TOC (<3%) and hidrogen index - HI, (100-400 mg HC/g). The other is well-preserved marine facies in continental slope to abyssal sea, with high TOC (>3%) and high HI (max 900 mg HC/g TOC). Molecular fossils originating from aryl carotene are the indicator of the existence of euphotic zone in the ancient ocean. The compounds of aryl isoprenes and sulfurous aryl isoprenes are detected in the black shale samples of well DSDP 367. They rooted in photosynthetic green sulfur bacteria and the carbon isotope value of these compounds is higher 10~15 than those of fossil molecules of algae and cyanobacteria. Two packages of oil-prone source rocks separately occurr in the Aptian- Albian of Lower Cretaceous and Cenomanian-Turonian of Upper Cretaceous. High-graded marine source rocks of the Senegal Basin may occur in a sulfurous, anoxic deep-water environment with sufficient carbon sequestration. [ABSTRACT FROM AUTHOR]

Upper Cretaceous mudstones are the most important source rocks in the Termit Basin, SE Niger. For this study, 184 mudstone samples from the Santonian-Campanian Yogou Formation and the underlying Cenomanian-Coniacian Donga Formation from eight wells were analyzed on the basis of palaeontological, petrographical and geochemical data, the latter including the results of Rock-Eval, biomarker and stable isotope analyses. Samples from the upper member of the Yogou Formation contain marine algae and ostracods together with freshwater algae (Pediastrum) and arenaceous foraminifera, indicating a shallow-marine to paralic depositional environment with fresh- to brackish waters. Terrestrial pollen and spores are common and of high diversity, suggesting proximity to land. Samples from the lower member contain marine algae and ostracods and arenaceous foraminifera but without freshwater algae, indicating shallow-marine and brackish-water settings with less freshwater influence. The wide range of gammacerane index values, gammacerane/C30 hopane (0.07-0.5) and Pr/Ph ratios (0.63-4.68) in samples from the upper member of the Yogou Formation suggest a low to moderately saline environment with oxic to anoxic conditions. In samples from the lower member, the narrower range of the gammacerane index (0.23∼0.35) and Pr/Ph ratios (0.76-1.36) probably indicate a moderately saline environment with suboxic to relatively anoxic conditions. Petrographic analyses of the Yogou Formation samples show that organic matter is dominated by terrestrial higher plant material with vitrinite, inertinite and specific liptinites (sporinite, cutinite and resinite). Extracts are characterized by a dominance of C29 steranes over C27 and C28 homologues. Results of pyrolysis and elemental analyses indicate that the organic matter is composed mainly of Type II kerogen grading to mixed Type II-III and Type III material with poor to excellent petroleum potential. Mudstones from the upper member of the Yogou Formation have higher petroleum generation potential than those from the lower member. Mudstones in the Donga Formation are dominated by Type III organic matter with poor to fair petroleum generation potential. Geochemical parameters indicate that in terms of thermal maturity the Yogou Formations has reached or surpassed the early phase of oil generation. Samples have Tmax values and 20S/(20S+20R) C29 sterane ratios greater than 435°C and 0.35, respectively. 22S/(22S+22R) ratios of C31 homohopanes range from 0.50 to 0.54. The results of this study will help to provide a better understanding of the hydrocarbon potential of Upper Cretaceous marine source rocks in the Termit Basin and also in coeval intracontinental rift basins such as the Tenere Basin (Niger), Bornu Basin (Nigeria) and Benue Trough (Nigeria). [ABSTRACT FROM AUTHOR]

To analyze the dominant factors of the origin of marine source rocks of the northern South China Sea (SCS), this paper focuses on the Lower Oligocene neritic source rocks in the Baiyun Sag of the Pearl River Mouth Basin. This study assesses the source rocks based on the principles and methods of sedimentology, geochemistry, and palynology and data on pyrolysis parameters, biomarker compounds, major and trace elements, and sedimentary organic debris. The paleoproductivity, input of terrigenous organic matter (TOM), redox conditions and sediment flux are characterized by the above parameters. The dominant effects of organic matter (OM) supply, preservation, and dilution on the origin of the source rocks are studied, and a depositional model of the source rocks is established. Finally, the origin of the Lower Oligocene marine source rocks in the northern SCS is clarified. The results show that the main source of the marine source rocks was terrestrial higher plants, while the contribution of planktonic algae was small. The origin of the marine source rocks was strongly controlled by the input of TOM during the depositional period. The source rocks developed in an oxic environment, and the correlation between the redox indices and OM abundance is poor, which indicates that the redox conditions were not the main factor dominating the origin of the source rocks. With an increase in the sediment flux and the barrier formed by low uplifts, the dilution of the OM decreased, and the contact time between OM and oxygen was markedly reduced; therefore, some OM in the oxic bottom water was not oxidized but instead became enriched, thereby forming the source rocks. • Characteristics of geochemistry and palynofacies of source rocks were analyzed. • Lower Oligocene marine source rocks were developed in an oxic environment. • Terrigenous organic matter supply was the main controlling factor of source rocks. • High sediment flux and barrier of low uplifts reduced the organic matter dilution. [ABSTRACT FROM AUTHOR]