Seismic stratigraphy of the Eocene northern continental margin of the Santos basin (Brazil): relationships between platform and turbidite systems read from depositional sequences.

Because of a high siliciclastic sediment supply rate, the Eocene Brazilian passive margin shows sedimentary geometries that differ from the classical models. Two orders of sequences or cycles have been identified: 1.5-9 and 1 2 My. During high rates of accommodation and low sediment supply, at a 12 M y time-scale, ramp morphologies occur with well developed transgressive and highstand systems tract and shelf margin wedges, at 1.5-9 My intervals, wh ereas turbiditic deposits are rare to non-existent. During low rates of acc ommodation and high sediment supply, at a 12 My time-scale, a slope morphol ogy is built with well-expressed aggradational transgressive and lowstand s ystems tracts at 1.5 My intervals. Within transgressive and highstand syste ms tracts, turbiditic sedimentation occurs because of the increasing slope during aggradation of shelfbreak deposits. (C) 2001 Academie des sciences / Editions scientifiques et medicales Elsevier SAS.