--> Abstract: Basin, Swells, Volcanoes and Turbidites: Continental Scale Controls on Deep Water Sand Input to African Margins, by Duncan S. Macgregor and Kevin Burke; #90072 (2007)

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Basin, Swells, Volcanoes and Turbidites: Continental Scale Controls on Deep Water Sand Input to African Margins

Duncan S. Macgregor1 and Kevin Burke2
1Neftex Petroleum Consultants, Oxford, United Kingdom
2University of Houston, Houston, TX

The Cenozoic history of the African continent can be recorded in two megasequences. Prior to the Oligocene, Africa was a flat continent, with regionally correlative marine transgressions extending far into the continental interior. From then onwards, a subtle interaction existed between rising plume-derived swells and ice-volume fluctuations in East, later West Antarctica and Greenland. Swell uplift, associated with volcanism, peaked in the period 20-10Ma in North and West Africa and in the period 8-2Ma in Southern and East Africa. The amounts eroded from the swells are considerable, particularly the Ahaggar, leading to the formation of the large deltas of Africa and the deepwater reservoirs associated with them. The oldest known deepwater reservoirs are aged around 20-22Ma in the large deltas, with maximum sediment input and delta progradation usually being younger than 17Ma. Smaller deltas may show more limited pulses of deepwater sand input, probably tied to peaks of plume uplift, eustatic lowstands and climatic variations. Many such deltas, particularly in now-aridified Saharan Africa, are now extinct, including examples in Mauritania and the Sirt Basin. Eustacy has become dominant again during the past 3 My, particularly the last 0.8 My, due to Eurasian ice volume fluctuations. Understanding these interactions is key to determining reservoir risk off the smaller deltas, predicting sands associated with now-extinct deltas, and analysing the undrilled deeper sections of the large deltas. Understanding swell uplift and erosion is also key to predicting the level of source rock maturity in onshore basins, which may often be underestimated.

 

AAPG Search and Discovery Article #90072 © 2007 AAPG and AAPG European Region Conference, Athens, Greece