Architectural hierarchy of two juxtaposed slope channel complex sets in the Laingsburg depocenter, Karoo Basin, South Africa

Characterization and understanding of outcrop analogous enhance facies models of deep-water systems and provide the detailed architectural properties required to construct more accurate reservoir models. In the southwest Karoo Basin, South Africa, Units C and D of the Permian Laingsburg Formation are continuously exposed along 10 km-long WNW-ESE trending ridges that provide excellent outcrop examples of two erosionally juxtaposed channel complex sets. A correlation panel built with 184 logs at 20 m spacing (about 13 km of measured stratigraphy) provides a rare opportunity (i) to identify a hierarchy of architectural elements and their vertical and lateral stacking patterns and (ii) to develop better predictive models of reservoir properties. Three orders of hierarchically-organized physical stratigraphic elements can be defined at seismic and sub-seismic scale. The lowest order element in the scale is comprised of two channel complex sets each bounded by 50-100 m-deep and 2000-3000 m-wide composite erosion surfaces. Within these major cuts, smaller-scale erosional surfaces define 30-90 m-deep and 300-2000 m-wide channel complexes. Each complex consists of two or more 2-30 m-deep and 100-500 m-wide channel-fills of similar architectural style. Statistical data, such as net-to-gross ranges, infill facies type, magnitude of erosion, and aspect ratios have been determined for each level of hierarchy. Stacking patterns of the channel complexes within the two sets is very different. In the older set (Unit C) they preserve an overall compensationally stacked architecture, whereas in the younger set (Unit D) they display a progressive westward shift in the locus of erosion and deposition.