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Tectonic Development, Sedimentation and Palaeoceanography of the Mozambique Channel During the Tertiary


The bottom current circulation along continental margins is shaping their morphology and affecting their sedimentary evolution. However, a better understanding of the processes that link the bottom circulation and continental slope features is needed. The Mozambique Channel is the northernmost part of the deep Mozambique basin, developed along the eastern African margin. The tectonic setting and the basin evolution of this area is related to the break-up of Gondwanaland. The basin hosts a record of sediments since the Jurassic separation of East Gondwana (Madagascar, India, Australia and Antarctica) and West Gondwana (Africa and South America). We characterized the main stratigraphic framework of the basin by analyzing the available seismic profiles. We identify eight major stratigraphic units that were deposited during the Tertiary. The construction of time isopach maps for each unit based on seismic facies changes and unconformities reveals the sedimentary infill of the Mozambique Channel. It supports the interpretation that the evolution of the basin was influenced both by the occurrence of the Beira-High, a SW-NE elongated basement horst interpreted as a continental crust fragment detached from the Mozambique continental margin, and bottom-currents interfering with sedimentation. A giant contourite drift system was developed from the Upper Cretaceous to the Early Miocene with a main growth stage during the Oligocene. The main phase of the drift development during the Oligocene was influenced by the onset of Antarctic Bottom Water and Circumpolar Deep Water coeval with the opening of the Drake and Tasmanian Passage. During the Early Miocene, the onset of the North Atlantic Deep Waters (NADW) might have forced the deepening of the AABW and became progressively dominant in the Mozambique Channel. It might be inferred that this change has caused the burial of the drift from the Middle Miocene times. In the Middle Miocene the Zambezi delta was deflected to the NE by the topography, deposited in the Angoche basin due to confinement by the giant drift in the South. From the Late Miocene to the Pleistocene, the Zambezi fan progressively prograded on the both sides of the giant drift into the open basin to the South. The results that we report here should prove essential for understanding the evolution of the basin and the increasing role played by bottom-currents at a global scale.