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The Vema contourite fan in the South Brazilian basin

2002; Zoological Society of London; Volume: 22; Issue: 1 Linguagem: Inglês

10.1144/gsl.mem.2002.022.01.15

2041-4722

Jean‐Claude Faugères, Sébastien Zaragosi, Marie‐Laure Mézerais, Laurent Massé,

Geological and Geophysical Studies

Abstract The Vema contourite fan is a Neogene mud-rich accumulation (200-400 m thick), fed by Antarctic Bottom Water bottom currents and located downstream of the Rio Grande Rise. It forms one single, mounded, fan-shaped body deposited between two major channels through which the main part of the deep AABW circulation is funneled. A suite of cores and seismic lines have been collected over the whole area. The sediments deposited below the shear zone between the two current branches consist almost exclusively of muddy contourites, either homogeneous in structure or micro-brecciated. Manganiferous deposits occur in the vicinity of the channels and on the channel floors. As a result of the morphological and hydrological background, the contourite drift has prograded mostly downstream. It is composed of several depositional units bounded by widespread discontinuities showing erosional patterns. This geometry results from an alternation of episodes of strong and unstable erosive currents, and periods of relatively weak and stable depositional currents