부산대학교 도서관

Major changes in watermass chemistry during the opening of the central segment of the South Atlantic, and oceanic anoxic events (OAEs 1a to 1d), represent dramatic events that affected the ocean–atmosphere system during the Early Cretaceous. This thesis addresses the chemostratigraphic correlation of Tethyan and South Atlantic sections based on carbon-, sulphur- and strontium-isotopes (δ13C, δ34S and 87Sr/86Sr) integrated with other methods to explore the causal links between these phenomena. Firstly, the sedimentation of massive evaporite deposits is discussed and its relationship with the Early Aptian OAE 1a explored. The proposed coincidence in timing between massive evaporite deposition and OAE 1a enhances the understanding of carbon and sulphur cycles in the Early Cretaceous. Secondly, the top of sub-evaporite carbonates in the southern Brazilian basins is identified as having been deposited in a continental environment, and further evidence for its deposition during part of the OAE 1a interval is presented. Thirdly, it is suggested that the formation of the Ontong Java Plateau, already linked to the genesis of OAE 1a, promoted a eustatic sealevel rise responsible for rapid seawater entrance into the southern Brazilian basins during the Early Aptian. Fourthly, the first record of OAE 1a from northeastern Brazil (Sergipe- Alagoas Basin) has been recognized, allowing stratigraphic correlation with southern Brazilian basins. Stratigraphic correlation between the southern Brazilian basins is extended to the Falkland Plateau, where the decrease in the content of organic matter upwards in the stratigraphy of DSDP Site 511 through the Barremian–OAE 1b interval can be related to the evolution of South Atlantic basinal geometry. Finally, in the context of a Tethyan reference section, the record of the Barremian-Aptian boundary and the OAE 1a interval has been characterized in the Tethyan Poggio le Guaine scientific core from Marche–Umbria, Italy.