Print this pageAAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
The Distribution of Deepwater Reservoirs and Depositional Environments: Can They Really Be Controlled by Crustal-Mantle Interactions? Evidence from the African Atlantic Margin
(1) University of Leeds, Leeds, United Kingdom.
As exploration progressively focuses on deep water settings in the South Atlantic there is much attention on developing a better understanding of reservoir distribution and depositional environments. The key structural aspect that control many of these systems are the gravity driven system including coupled deep water fold and thrust belts and updip extensional systems. Little attention is paid to the mechanism and genesis of long term margin instability.
We document the architecture and timing of margin deformation along the Namibian and South African margin.The margin shows evidence of high amplitude uplift events during the Late Cretaceous but we demonstrate that they are relatively short wavelength and have a short duration. The location of maximum uplift is co-incident with that of significant margin instability and gravity sliding. Furthermore, there is more uniform uplift during the Tertiary but that this is a longer wavelength event and does not result in such substantial margin instability.
We argue that neither uplift event can be accounted for by existing simple 1D stretching models or through horizontal compression. The advantage of this portion of the Atlantic is the absence of salt, therefore, salt driven tectonics can be also excluded. Rather, we suggest that it is crustal-mantle interactions that control the uplift events. The difference between Late Cretaceous and Tertiary events indicates different styles of crust-mantle interactions, although both have a profound effect on the deep water hydrocarbon systems, sediment supply onto the margin, the distribution of reservoir intervals, depositional environments and hydrocarbon maturation. A better constraint on large -scale controls on margin evolution is, therefore, essential for understanding reservoir-scale exploration questions.