Cretaceous to Recent Submarine Fans in the Southeast Angola Basin

There have been three periods in the past 100 m.y. during which sedimentation at Site 530 in the S.E. Angola Basin has been dominated by mass gravity processes. These three successions, each between 200 m and 300 m thick, can be interpreted as deep-sea fan accumulations on the basis of their morphology, seismic stratigraphy, and facies sequences and have been informally named the "brown," "white," and "green" fans from the colors of their dominant sediments. They are composed dominantly of pelagic, carbonate, and volcanogenic turbidites, respectively, all derived primarily from the Walvis Ridge immediately to the south. The average rate of sedimentation for each of the brown and green fans was 2-3 cm/1000 yr., but the frequency of (sandy) turbidites on the green fan (1/ 2,500 yr.) was an order of magnitude higher than for the (muddy) brown fan (1/25,000 yr.). Surprisingly, the brown fan sediments are more proximal than those of either the green or white fans. The primary controls on sedimentation in each case were different and included tectonic activity, paleogeography, sediment type, oceanic circulation, and sediment instability.