The Oligocene to Quaternary Zambezi Depositional System (Mozambique Channel, Southwest Indan Ocean) : architecture, sedimentation and forcing factors

The Zambezi turbidite system (Mozambique Channel, Western Indian Ocean) is one of the largest turbidite systems in the world and yet still remains poorly understood. Newly acquired high-resolution multibeam bathymetry, seismic reflection and sedimentological data allowed to investigate the architecture evolution and depositional patterns since the Oligocene in order to understand the main forcing factors that control the deep sea sedimentation in the Mozambique Channel. It was found that the Zambezi turbidite system is composed of two adjacent depositional systems: the channelized Zambezi Fan and a semiconfined fan in the lntermediate Basin. Moreover, results and interpretations indicate: (1) important tectonic control since the Miocene that caused deep incision of the Zambezi Valley and limited overflow of turbidite currents; (2) an important influence of bottom-currents that induces scarcity of fine-grained turbidites, valley flanks erosion and widespread occurrence of sediment waves; (3) low turbidite activity for the last 700 kyr that shows no relationship with sea-level changes as turbidite activity occurred irrespective of glacial or interglacial periods; (4) peaks in terrigenous flux with maxima in local summer insolation, reflecting that monsoon controls the sediment inputs towards the deep marine depositional system; (5) an on-off evolution of the Zambezi Fan that demonstrates a depocenter shift from the distal Zambezi Fan to the proximal Intermediate Basin. All our findings underline the high complexity in depositional environments of the Zambezi turbidite system.