CLIMATE EVENTS AND THEIR BEARING ON TURBIDITE CHANNELS OF THE CONGO FAN

The Congo Fan is a huge deep water fan with high sedimentation rate since Oligocene, decorated by widely developed turbidite channels, which provided excellent geologic conditions for hydrocarbon to accumulate. To recognize the key controlling factors and distribution patterns of these channels, it is significant to establish the stratigraphic frameworks by dating sediments, dividing evolutionary phases and defining isochronous geological events. Based on a comprehensive analysis of logging, seismic and palaeontological data, two 2^nd order and eight 3^rd order sequences have been identified. The age of each sequence boundary is dated by biostratigraphic evidence and global sea-level cyclicities. Under the sequence stratigraphic framework, three evolutionary periods of turbidite channels have been recognized: the rapid filling period of Late Oligocene, the stable depositional period of Early-Middle Miocene, and the massive channels developing period of Late Miocene. The three periods are closely related to the three uplifting events widely observed in the West African coastal basins. In addition, palynological assemblages suggest that climate changed very frequently in Miocene. And the massive channels developing period is in response to the cooling events when the sea-level dropped rapidly. Therefore, the development of turbidite channels is mainly controlled by both the tectonic and cooling events in West Africa. They are supplementary to each other and have joint effect on the development of channels.