Hodgson, David1, Rosalind King1, Richard Wild1, Shaun
Waite1, Stephen Flint1, David Hodgetts1
(1) University of Liverpool, Liverpool, United Kingdom
ABSTRACT: 3-D Model of a Channelized Lower Submarine Slope from the Tanqua Depocentre, SW Karoo Basin, South Africa
The range of sedimentary environments and depositional and post-depositional processes that occur in submarine slope systems makes their accurate 3D modeling a challenge. An added complication in foreland basin settings is post-depositional folding and thrusting. Unit 5 of the Skoorsteenberg Formation is a 100-m thick succession with abrupt lateral facies changes. Detailed sedimentary logging and high-resolution cross-sections has produced an accurate model of Unit 5 in the Hangklip area. Unit 5 is dominated by two SW-NE trending sharp-based bodies of thick-bedded structureless and dewatered sandstones with numerous internal erosional surfaces up to 15 m in depth that are interpreted as submarine channel complexes. The dominant facies between these channel complexes are thin-bedded ripple-laminated turbidites intercalated with deformed sandbodies, interpreted to have formed under a range of soft-sediment deformation processes from slope creep to slumping, indicating local gradients. This facies association is interpreted as an overbank environment. Absence of significant levees and the high amount of sandstone preserved in the channel complexes support a lower slope environment. The structural model was constrained by high-resolution cross-sections displaying low amplitude periclinal folds related to low-angle thrusting. The periclinal folds are key to modeling the location, orientation and tip points of surface and sub-seismic thrusts in the area. For modelling purposes, Unit 5 was separated into 4 zones based on significant erosion surfaces that bound channel complexes. The model was populated with object dimensions from 7 facies that were constrained from outcrop measurements and analysis of continuous digital helicopter-based photopanels.
AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.