Abstract
This paper is an attempt to show how one may discriminate turbiditic and contouritic processes in the deposition of deep-sea accumulations. The case study is the Sao Tomé deep-sea ‘channel levee’ system in the South Brazilian Basin. This system is elongated parallel to the margin contour, and was first interpreted as being controlled by contour current activity. Detailed analyses of 3.5-kHz profiles and piston cores allowed to demonstrate that the Upper Quaternary sediments are predominantly deposited by turbidite and hemipelagic–pelagic sedimentation processes. On the levee and the transitional area towards the deeper rise, frequent fine-grained turbidites, accounting for 25–45% of the entire depositional series, are interbedded with the hemipelagic–pelagic muds. In the channel, thicker and coarser turbidites (15%) are associated with debris-flows (20%). Deposit deformation in the form of slides, slumps and diapir-like structures largely affect the distal transitional area. Slight evidence of contour current activity only consists of some sediment wave fields and manganiferous-rich layers or some top-truncated sequences and foraminiferal sandy layers.
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