The role and the record of ocean currents in the sedimentary deposits of the continental margins: the margin of the SE Brazilian Basin

• Main Author: Viana, A.R.
• Other Authors: Petrobras, Université Bordeaux I, EPOC 5805 - Environnements et Paléoenvironnements Océaniques, Jean-Claude Faugères
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 1998
• Subjects: deep-water; sedimentology; Campos Basin; cold-water corals; Atlantic Ocean; marine geology; contourites; sedimentologie; géologie marine; Bassin de Campos; coraux d'eaux froides; turbidites; Océan Atlantique; [SDU]Sciences of the Universe [physics]; [SDU.STU]Sciences of the Universe [physics]/Earth Sciences; [SDU.STU.AG]Sciences of the Universe [physics]/Earth Sciences/Applied geology; [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography; [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces; environment; [SDU.STU.ST]Sciences of the Universe [physics]/Earth Sciences/Stratigraphy; Antarctic; The Antarctic; Antarc*
• Online Access: https://tel.archives-ouvertes.fr/tel-02061073; https://tel.archives-ouvertes.fr/tel-02061073/document; https://tel.archives-ouvertes.fr/tel-02061073/file/VIANA_AR_these%20doctorat.pdf

This work consists on a synthetic state of art upon the sedimentation mechanisms on the Campos margin, SE Brazil. It takes into account the available PETROBRAS data set face to modern literature on oceanography, sedimentology, sedimentary hydrodynamics and its modelling. The main goal is to clarify and quantify the impact of the ocean currents on sedimentation and their interaction with gravity processes.On the upper margin, Brazil Current (BC) activity is the main agent controlling modern sedimentation. BC intensity and core position change in response to morphologic modifications. Bottom current speeds at 200m water depth can reach more than 1 m/s. Coarse sediment transport, sea-floor erosion, hydraulic dunes development, burying of the São Tomé canyon (STC) head and sand accumulation on the upper slope are related to the BC activity.A conceptual model for the upper slope sand deposition and a paleoceanographic reconstitution for the upper Campos margin are also proposed. The model suggests that upper slope sand accumulation is enhanced during rising and high-stand sea-levels. The paleoceanographic reconstitution indicates that the last glacial corresponds to a BC low activity period. It was re-started from the last glacial maximum up to the Recent. On the lower slope, a depositional hiatus is observed between 16,000 and 12,500 years BP. It corresponds to an intensification and widening of the Antarctic Intermediate Water (AAIW) flow. The AAIW activity during this period is also correlated to the modern erosion of the Albacora Escarpment.Turbidite deposits found on the slope base and on the upper continental rise keep compositional and stratigraphic similarities, indicating that strong gravity currents from the upper margin passed across the São Paulo Plateau and built important sediment accumulations beyond 3,500 m, essentially during strong sea-level falls. Early Holocene turbidites are found at the STC mouth.Ancient outcrops studies highlighted the role of the oceanic currents in the sand accumulation on ...