Stratigraphic evolution of the upper slope and shelf edge in the Karoo Basin, South Africa
R. Wild, S.S. Flint and D.M. Hodgson
Journal name: Basin Research
Issue: Vol 21, No 5, October 2009 pp. 502 - 527
Special topic: Trajectory Analysis in Stratigraphy
Info: Article, PDF ( 5.59Mb )
The Permian EccaGroup of the Karoo Basin, South Africa preserves an extensive well- exposed siliciclastic basin £oor, slope and shelf- edge delta succession. The Kookfontein Formation includes multiple sedimentary cycles that display clinoform geometries and are interpreted to represent the deposits of a slope to shelf succession. The succession exhibits progradational followed by aggradational stacking of deltaic cycles that is related to a change in shelf- edge trajectory, and lies within two depositional sequences. Sedimentwas transferred to the slope via overextension of deltas onto and over the shelf edge, resulting in failure and re-adjustment of local slope gradients.The depositional facies and architecture of the Kookfontein Formation record the change from a bypassto accretion-dominated margin, which is interpreted to re£ect a decrease in sediment transport efficiency as the slope gradient decreased, slope length increased and shelf-edge trajectory rose. During this time the delivery system changed from point- sourced basin- £oor fans fed by slope channels to starved basin- £oor with sand-rich slope clinoforms. This is an example of a progradational margin inwhich the younger slope system is interpreted to be of a different style to the older slope system that fed the underlying sand-rich basin floor fans.