Slumping and Sediment Storage at the Shelf‐Edge: A Case Study From the Kookfontein and Waterford Formations, Tanqua Karoo Depocenter, South Africa

ABSTRACT A low‐gradient shelf‐edge delta system preserved at the Katjiesberg outcrop in the northern Tanqua Karoo depocenter (South Africa) records the evolution from shelf‐ to slope‐depositional processes in a fine‐grained sandstone dominated system. Lateral and vertical facies associated with slumping and other soft‐sediment deformation features at near seismic scale (~1 km laterally, ~100 m vertically) are documented. Stratigraphic correlations of these units using measured sections and ~3 km of digital outcrop models document the stratigraphic position of two shelf‐edge inflection points, which implies progradation of the shelf‐edge. Progradation and aggradation of detached slump deposits and their transition into dominantly in situ deformation features are consistently representative of the evolution from slope‐to‐shelf through time. The exposed Permian–Triassic Kookfontein Formation prodelta/slope succession at Katjiesberg is likely a time‐correlative deposit to clinothem cycles previously described 10s of km up depositional‐dip to the southwest. Katjiesberg represents the more distal expression of these cyclothems in the lower Kookfontein Formation, whereas the upper cycles are interpreted as collapse‐dominated clinothems that are overlain by basinward prograding mouthbar deposits of the Waterford Formation. This study highlights intra‐basinal process regime variability and facies expressions within a preserved shelf‐edge delta system. Results underscore the role of slump features in characterising clinothems and signalling clinothem rollover, which is particularly useful in low‐gradient systems with subtle clinothem geometry. The characterisation of low‐gradient clinothem geometries and variability in this shelf‐edge delta system improves our understanding of shelf‐margin accretion and deepwater sediment delivery across the shelf and slope.