Clay mineral associations and structural evolution of the South Atlantic: Jurassic to Eocene
Abstract Clay minerals have been used to reconstruct the geological history of the South Atlantic. Six mineralogical stages have been recognized from the Middle Jurassic to the Eocene: 1. (1) Prior to the Oxfordian, illite, irregular mixed-layers and kaolinite marked a period of tectonic extension between Africa and Antarctica. 2. (2) From the Oxfordian to the Early Albian, smectites developed during subsidence-induced peneplanation of the relief along the southern margin, while chlorite, illite, irregular mixed-layers and kaolinite characterized a distensive regime in the Cape and southern Angola basins. 3. (3) From the Albian to the Early Turonian, smectites, palygorskite and sepiolite linked to subsidence processes occurred from the Southern Ocean to the southern Angola Basin, while chlorite, illite, irregular mixed-layers and kaolinite characterized tectonic extension from Gabon to Nigeria. 4. (4) From the Early Turonian to the Early Campanian, smectites, palygorskite and sepiolite linked to subsidence were widespread in the South Atlantic areas. 5. (5) From the Early Campanian to Early Paleocene, chlorite, illite, irregular and subregular mixed-layers and kaolinite marked a reactivation of continental reliefs in the northern areas of the South Atlantic, in relation to compression in Nigeria and opening of the Equatorial Atlantic. 6. (6) After the Early Paleocene, smectites, palygorskite and sepiolite characterized the widespread subsidence in the South Atlantic.