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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 77 (1993)

Issue: 6. (June)

First Page: 963

Last Page: 979

Title: Sedimentary Geology and Evolution of an Outcropping Shelf-Margin Delta, Late Proterozoic Wonoka Formation, South Australia

Author(s): P. A. DiBona (2), C. C. von der Borch (3)


Discrete sand units or accumulations crop out within the late Proterozoic Wonoka Formation, northern Flinders Ranges, South Australia. These sand wedges are unique in their size, contacts, facies, and associations to other sands in the formation and are interpreted as shelf-margin deltas. The wedges can be divided into a main body and a series of discrete feeder channels. The main body consists of basal slump masses, a sandstone-dominated succession, and an overlying shale-dominated facies. Lithofacies grossly define a deepening-upward succession from a lower shoreface to outer shelf setting.

The formation and deposition of the feeder channels and sand wedges was controlled largely by relative sea level changes. Initial exposure of the shelf and subaerial erosion produced a regional erosional surface and incised valleys across the paleoshelf. Prior to deposition of the wedges, slope instabilities and minor uplift occurred. Sediment was then transported across the shelf and deposited near or at the shelf break and reworked in a shallow marine environment. Deposition of the shelf-margin deltas continued during relative sea level rise, but ended with shelf drowning.

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