External Controls on Deep-Water Depositional Systems
The principal objective of the meeting from which this set of papers arose was to gain an overview of the current state of knowledge of the roles and interplays of external controls on deposition in deep marine environments. By external controls we mean allocyclic or allogenic factors, i.e., those that are unrelated to the self-organization of the depositional system (autocyclic or autogenic); principal among these are climate, sea level, sediment supply, and tectonics. One of the big questions that the meeting sought to address concerned the comparability of the recent high-frequency, high-resolution record with the older, generally lower-frequency stratigraphic record of “deep time”; to what extent are the apparent differences a function of resolution, or of comparisons between a glacial and a nonglacial Earth? In fact, as the papers in this volume illustrate, the variability between individual systems, even in Late Glacial time, and the paucity of constraints on older systems makes these questions difficult to answer, but some useful conclusions can be drawn. The papers presented at the meeting were organized into themes that included: overviews of glacial sea-level change, and of climate modeling; external controls on large river-fed submarine fans, including the effects of climate and sea level on the fluvial system itself; influences of climate, sea level, and tectonics on a range of smaller modern systems; deep marine processes; the outcrop record of the pre-Pleistocene Earth; the subsurface record of the pre-Pleistocene Earth; and syntheses. The organization of the volume largely reflects this structure.
Development of Subaqueous Fold Belts as a Control on the Timing and Distribution of Deepwater Sedimentation: An Example from the Southwest Karoo Basin, South Africa
Published:January 01, 2009
Rosalind C. King, David M. Hodgson, Stephen S. Flint, Graham J. Potts, Belinda Van Lente, 2009. "Development of Subaqueous Fold Belts as a Control on the Timing and Distribution of Deepwater Sedimentation: An Example from the Southwest Karoo Basin, South Africa", External Controls on Deep-Water Depositional Systems, Ben Kneller, Ole J. Martinsen, Bill McCaffrey
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The sediment source area for foreland-basin fills is typically inferred to be the adjacent fold-and-thrust belt. In the case of the Karoo Basin, South Africa, however, the Cape Fold Belt (CFB) was not the source during the early phase of basin filling. Instead, the Permian deepwater siliciclastic sediments of the lower Ecca Group were derived from a granitic source area outboard of the adjacent orthoquartzitic fold belt. Lithofacies, stratal thickness, and paleocurrent distributions indicate that seabed deformation occurred during deposition. Sediment was supplied across an evolving but submerged proto-CFB through a major syncline that acted as a long-lived single delivery point to the submarine slope. Northward migration of the deformation front and the subsequent uplift of the CFB, notably in the eastern parts of the syncline, forced another sediment route to develop 100 km north from the Laingsburg depocenter to the Tanqua depocenter.