Salt Tectonic Controls on the Location and Evolution of Submarine Lobe-Channel-Levee Complexes: Miocene, Offshore Angola

Abstract

Coherence and RGB-blended spectral decomposition volumes calibrated by cross-sectional seismic facies, allow for high resolution imaging of deepwater depositional systems and their interaction with salt-related sea floor topography. Key structural controls on the location of major sediment transport pathways and the local interaction between lobe-channel-levee systems and individual salt-related structures were: the length and height of structures, the location and geometry of segment boundaries, the growth and linkage of individual structures, and the incidence angle between structural strike and flow direction. Where the regional flow direction was at a high angle to structural strike, transport pathways passed progressively through multiple intraslope basins in a fill and spill manner. Segment boundaries and structural lows between diapirs acted as spill points, focusing sediment transport between intraslope basins. Channel-lobe transitions are commonly associated with these spill points, where flows experience a change from lateral confinement as they pass through segment boundaries to relative unconfined in the down-dip depocentre. Where regional flow direction was at a low angle to structural strike, sediment transport pathways ran parallel to structure and were confined to individual intraslope basins for many tens of kilometres. Furthermore, spill between intraslope basins was rare in these cases. The major sediment transport pathways were used repeatedly during the Miocene, giving rise to vertically stacked lobe-channel-levee complexes along the pathways. Shadow zones devoid of coarse clastics developed in areas that were either structurally isolated from the sediment transport pathways or bypassed as a result of channel diversion. This large-scale stratigraphic architecture was largely controlled by the position of main structures and their segment boundaries being fixed through the Miocene. The results of this study allow us to identify generic responses of lobe-channel-levee systems to arrays of salt-related structural deformation of the sea floor.

AAPG Datapages/Search and Discovery Article #90189 © 2014 AAPG Annual Convention and Exhibition, Houston, Texas, USA, April 6–9, 2014