Structural evolution of African basins: stratigraphic synthesis

摘要

AbstractThe structural and stratigraphic character of African interior sedimentary basins is highly variable, indicating contrasting basin‐forming mechanisms and subsequent subsidence histories. A stratigraphic database has been compiled for African interior depositional basins for the purpose of better understanding basin thermal and structural development. Data are recorded in the form of stratal age, lithology, thickness and elevation of top with respect to present sea level. The data are obtained from published structure contour maps, well sections, and outcrop geology and elevation. There are various degrees of data coverage of the basins, proportional to the amount of water and oil drilling activity. Consequently, there is excellent coverage of North African basins such as the Algerian basin and the Sirte basin, while there is little known about the subsurface of the Congo basin. The stratigraphic data are used to reconstruct the depositional history of the basins, while backstripping leads to the quantification of the thermo‐tectonic component of basin subsidence. The nature of basement subsidence can provide constraints on lithospheric flexural rigidity. In addition, the depositional and thermo‐tectonic history of each basin bears upon the mechanisms of basin formation and subsidence. Virtually all types of basins are represented in interior Africa, including thrust‐loaded basins (Algerian), passive‐margin rift basins (Algerian, Sirte), modern active rift basins (East African), ancient rift basins (Benue, Abu Gabra), basins caused by uplift of their margins (Congo, Chad, Illumeden) and even basins that may be related to thermal subsidence of hot‐spot domes (Alger