Integrating Core and Outcrop Data to Constrain the 4D Evolution of Submarine Channel Complexes: an Example from the Karoo Basin, South Africa

Morris, Emma A.¹; Hodgson, David M.; Flint, Stephen S.; and Brunt, Rufus L.
¹[email protected]

The evolution of submarine channel complexes can be documented using high resolution 3D seismic datasets. However, these studies provide limited information on the distribution of sedimentary facies of channel-fills, channel-scale stacking patterns, or the stratigraphic relationship with the adjacent levee/overbank deposits. Sub-unit C2 is a channel-levee system in the mud-prone submarine slope succession, of the Fort Brown Formation, Karoo Basin, South Africa, which crops out on both limbs of the post-depositional Baviaans syncline. C2 comprises thin-bedded siltstones and fine-grained sandstones interpreted as external levee, adjacent to channels filled with thick-bedded structureless sandstones, thin-bedded channel margin, and internal levee deposits. Behind outcrop research boreholes and well logs on the southern limb of the syncline intersect the C2-aged system in channel axis, internal levee, and external levee settings. Detailed sedimentary facies and channel stacking patterns identified in 1D can be placed within well-constrained 2-D outcrop correlation panels. Using correlation panels on both limbs of the syncline, key characteristics, such as depth of erosion, stacking patterns, and cross-cutting relationships, can be constrained allowing the correlation of submarine channel complexes and bounding levees across the syncline reconstructing palaeogeographic configurations for different channel complexes. This correlation indicates that the system evolved over time; from a deeply incised channel complex, to a series of external levee-confined laterally stepping channel complexes before developing into an aggradational channel complex confined by both internal and external levees. Channels in the proximal areas of the southern limb are relatively ordered and confined by external levees to a 3 km wide area resulting in channels preserved as remnants, however, this increases the potential for connectivity between channels. On the northern limb, these channel complexes are more widely spaced out over an 11 km cross-sectional area, therefore there is a higher rate of channel preservation but with a lower potential for connectivity between channels as external levee deposits are often preserved between channel complexes. This unique integrated dataset enables a better understanding of how the architecture and geometry of a suite of submarine channels has evolved through time.

AAPG Search and Discovery Article #90166©2013 AAPG International Conference & Exhibition, Cartagena, Colombia, 8-11 September 2013