Contourite sedimentation in the Falkland Trough, western South Atlantic
Published:January 01, 2002
Alex P. Cunningham, John A. Howe, Peter F Barker, 2002. "Contourite sedimentation in the Falkland Trough, western South Atlantic", Deep-Water Contourite Systems: Modern Drifts and Ancient Series, Seismic and Sedimentary Characteristics, D. A. V. Stow, C. J. Pudsey, J. A. Howe, J.-C. Faugères, A. R. Viana
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The Falkland Trough is a west-east bathymetric deep that separates the Falkland Plateau from the North Scotia Ridge in the western South Atlantic. It lies in the path of Circumpolar Deep Water flowing within the Antarctic Circumpolar Current (ACC), and Weddell Sea Deep Water flowing beneath the ACC east of Shag Rocks passage. Marine geophysical and sediment core data demonstrate the influence of ambient bottom currents on deposition in this area, and reveal two styles of contourite sedimentation: (1) deposition of glauconite-rich sandy contourites in exposed areas of the Falkland Plateau and Falkland Trough, where vigorous ACC bottom currents control sedimentation, and (2) deposition of biogenic sandy contourites, muddy contourites and hemipelagites (western Falkland Trough), and muddy diatom ooze (eastern Falkland Trough), in the form of two elongate sediment drifts, which have developed in the presence of more sluggish bottom currents. The drift sediments contain a depositional record of bottom current flow through the glacial cycle (southern-origin bottom water flow in the east, and probably ACC flow in the west); analyses of core data from the western Falkland Trough suggest a reduction in bottom current strength during the Last Glacial Maximum at present depths of > 2500 m below sea level.
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Deep-Water Contourite Systems: Modern Drifts and Ancient Series, Seismic and Sedimentary Characteristics
Countourites are a widespread but poorly known group of sediments linked to the action of powerful bottom currents in deep water. Although we know they are especially common along continental margins and through oceanic gateways, they have been surrounded by contoversy since they were first recognized in the early 1960s. Where correctly recognized and decoded they can provide one of the keys to our better understanding of bottom water circulation and of the ocean–climate link. They are part of the spectrum of deposits that confronts the oil industry as exploration moves into progressively greater water depths.
This memoir is an important outcome of the International Geological Correlation Project 432 on Bottom Currents, Contourites and Palaeocirculation. It includes 30 papers involving over 75 key scientists from around the world. Following an introductory state–of–the–art paper by the editors, there are 25 separate case studies on modern drifts and four on ancient contourite series. Each contribution highlights the specific geological and oceanographic setting, bathymetry, physiographic and stratigraphic context, seismic attributes and sedimentary characteristics of that drift. Case studies range from some of the well-documented North Atlantic drifts to those much less known from the Mediterrenean, from important syntheses of the Gulf of Cadiz and Vema Channel Gateway, to completely new data on South Atlantic, Pacific and Antartic margin systems. The four papers on ancient series from Japan, China and Cyprus serve to emphasise the complex nature and subtle characteristics of contourites, which make their identification a scientific challenge.
This volume is dedicated to the memory of Charlie Hollister (1936–1999), one of the founding fathers and pioneers of countourite research.