The Permian Laingsburg depocenter, Karoo Basin, South Africa is the focus of sedimentological and stratigraphic research as an exhumed analogue for offshore hydrocarbon reservoirs in deep-water basins. Thin-skinned thrust tectonics during the Permo-Triassic Cape Orogeny resulted in post-depositional deformation of the Permian basin-fill. Regional-scale cross sections reveal two structural domains: a southern domain in the Laingsburg depocenter comprising 8-11 km wavelength north-verging fault-propagation folding, driven by buried low angle (<45o) reverse faults that coalesce at depth as part of a mega-detachment below the Lower Paleozoic Cape Supergroup; and a northern domain to the north of the Laingsburg depocenter of short wavelength, low amplitude, asymmetrical folding facilitated by a detachment within the Permian Ecca Group. Five detailed structural cross sections permit the palinspastic restoration, and a calculation of the amount of shortening, across a 2500 km2 area in the Laingsburg depocenter. Average shortening across the study area is 16.9% (5.8 km), and decreases south to north. Shortening estimates from the Upper Ecca Group increase from 4.3 km near Matjiesfontein in the west to 10.4 km near Prince Albert in the east. Three dimensional restorations of stratigraphic surfaces are consistent with these figures (17%), and allow paleogeographic and isopach thickness maps to be resorted to their configuration at the time of deposition. Structural restoration can be routinely employed in outcrop studies to improve the accuracy of dimensions (e.g. volumetrics) and reconstructions (e.g. sediment dispersal patterns) derived from ancient sedimentary systems. The workflow presented here will add value to exhumed basin analogues by presenting pre-kinematic configurations at the frontal margins of fold-thrust belts.
CORE (COnnecting REpositories)
CORE (COnnecting REpositories)