Contourite depositional systems off the Mozambique continental margin (Mozambique Channel, SW Indian Ocean). / Thieblemont, Antoine.

2020. 118 p.

Research output: ThesisDoctoral Thesis

Unpublished

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Abstract

The Mozambique Channel locates in the Southwest Indian Ocean between the East African continental margin off Mozambique and Madagascar. On the Mozambican continental margin, apart from the settling of pelagic and hemipelagic particles, great thicknesses of terrigenous sediments have accumulated, being transported and deposited by three principal processes: mass-failures, turbidity currents, and contour currents. Despite this area represents an ideal setting to study these contour currents, their impact on sediments have been poorly studied. This Ph.D. work aims to develop our understanding of the mechanisms behind contour currents, controlling the formation of contourite depositional systems (CDSs) in the Mozambique Channel during the Cretaceous and Cenozoic. The broad data set available for this Ph.D. work includes high-resolution multibeam datasets, seismic data, hydrographic data, and results of a numerical model (a regional oceanic modeling system).
Present-day CDSs of the Mozambique Channel are recognized from the upper continental slope to the abyssal plain. These CDSs show a broad array of morphologies, comprising plastered drifts, elongated-mounded drifts, sediment waves, contourite terraces, moats, contourite channels, abraded surfaces, scours, and furrows. Bottom currents and secondary oceanographic processes (internal waves) control the morphology of CDSs. Other predisposing factors for their morphologies identified in the Mozambique Channel are the presence of seafloor irregularities and the proximity/intensity of sediment sources. Hydrodynamic modeling of the present-day oceanic circulation showed that seafloor obstacles serve to focus the flow path of bottom currents while periods and areas with high rates of sedimentation superimposed on the whole CDSs, triggering mass-failures and turbidity currents. In the ancient record, the onset and burial phases of CDSs are mainly driven by tectonics (with the opening, shoaling, and closing of major oceanic gateways), leading to major palaeoceanographic changes. Locally, their variable morphologies confirm the present-day studies where seafloor morphology and proximity/intensity of sediment sources play a significant role. Specific conditions, where it exists a relative equilibrium between long-term steady bottom currents flow and short-term turbidity currents, might have economic significance for the petroleum industry, occurring more specifically along the contourite terraces.
Original languageEnglish
QualificationPh.D.
Awarding Institution
Supervisors/Advisors
Thesis sponsors
  • TOTAL, R&D Frontier Exploration Program, Avenue Larribau, Pau, 64000, France
Award date1 Jun 2020
Publication statusUnpublished - 2020

ID: 38046790