The application of seismic and sequence stratigraphy to the post-rift megasequence offshore Namibia

Abstract

Abstract provided by author:

The passive continental margin offshore Namibia is a relatively under-studied area where information concerning the ages of individual geological events or the lithological nature of the offshore deposits is limited. The detailed interpretation of 2D regional seismic data from this region therefore requires a tool which enables the correlation of events and the prediction of lithologies, two factors which provide the basic premise of sequence stratigraphy. The application of seismic and sequence stratigraphic concepts to the post-rift megasequence offshore Namibia has resulted in the identification of five megasequences, based upon which a large scale, regional framework for this area can be constructed. Detailed seismic interpretation reveals a number of depositional anderosional processes (e. g. submarine canyons and channels, incised valleys, deltas and mass transport deposits), thought to characterise the different depositional environments of the continental margin. Based on the interpretation of these processes and also the identification of a number of Cretaceous and Tertiary third order depositional sequences, a sequence stratigraphic framework has been established for the post-rift megasequence, within which correlations to adjacent margins can be made. Seismic expressions of the different depositional systems, and therefore interpreted systems tracts, suggest that important modifications should be made to existing sequence stratigraphic models in order to develop a more comprehensive model for theNamibian continental margin. The incorporation of information from the onshore area and details of the tectonic subsidence history of the margin resolved from flexural backstripping studies carried out in this project, additionally enables a better understanding of the causes of relative sea level change, and thus the controls on sequence development, to be attained. Once established, the sequence stratigraphic framework can be used to predict the hydrocarbon potential of the post-riftmegasequence, resulting in a number of new play types being proposed for this largely frontier area