Although fine sediment represents an important proportion of sediment transferred by rivers, many studies of basin margin progradation emphasize supply and accretion of sand at and beyond the shelf edge. To understand how and when basin margin clinothems prograde in the absence of coarse-grained sediment supply to the shelf edge, Poyatos-Moré and others examine clinforms of the Permian Waterford Formation, in the Karoo Basin (South Africa). In these strata, normal and inverse grading, erosion surfaces, and moderate to low intensity of bioturbation are common in low-gradient (< 0.7°) clinoforms of thick, outer-shelf to upper-slope mudstone overlain by thin sandy shelf topset strata. The study provides a depositional model for shelf-to-slope transitions in fine grained successions, illustrating how progradational mud-rich, shelf-confined deltaic clinothems with muddy shelf-edge rollovers develop.
Mud-dominated basin-margin progradation: processes and implications by Miquel Poyatos-Moré, George D. Jones, Rufus L. Brunt, David M. Hodgson, Richard J. Wild, and Stephen S. Flint