La succession des sédiments dans les bassins marins et continentaux du Congo depuis le début du Mésozoïque

Abstract

This contribution is the result of initial investigations presented on sedimentary accumulations, from the beginning of the Mesozoïc, in the continental basin called Cuvette du Congo and in the marine basin of the near atlantic margin. Later researches of regional geology and of petroleum exploration provide new datas. The mechanisms of sedimentation are compared during the stages of opening, then of sea floor spreading of the south Atlantic Ocean. A long distensive tectonic phasis begins during the first jurassic subsidence and continues until Senonian ; a paroxysm is observed during Neocomian. A moderate compressive phasis begins at the Paleocene with a N 90-100 folds and reach a relative maximum during Lutetian with a N 110-120 orientation. At the Miocene, a distensive regime appears again while the continental flexure is going westward. The hot climate with an arid tendency of lower Cretaceous become increasingly tropical from the Albian down the Senonian. Toward the end of the Cretaceous and during Paleogene, a quiet intensis aridification phasis interferes. At the Neogene, the South Atlantic opening lets the apparition of a monsoon regime and then of a new tropicalisation. The sedimentation balance is a direct result of tectonic deformations and climatic changes. High rates of detritic accumulations, rubéfactions, continental silicifications and glauconitisation episodes are taking into account. This study is also a first introduction to the present contribution of the Congo river to the ocean.