Seismic stratigraphic framework and depositional history for Cretaceous and Cenozoic contourite depositional systems of the Mozambique Channel, SW Indian Ocean

Abstract

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Lateral migration of large sedimentary bodies in a deep-marine system offshore of Argentina

“…The lateral upslope migration of M increasingly confines C, and by SU3, exhibits a westward shift into C. In contrast to other giant drifts in the region however, M shows no vertical growth 18 . The deeper AABW/CDW interface at this time appears to have imposed a vertical height limit on the CDS similar to that proposed for the Zambezi drift 11 . Secondary oceanographic processes, such as internal waves at this location, may cause enhanced erosion of the steep basinward flank of M 8 .…”

“…However, in the absence of an observed feeder channel (or submarine canyon), and given the clear alongslope orientation and lateral continuity of the depositional and erosional features along the continental rise (rather than in the downslope orientation typically assumed by mixed turbidite-contourite systems), we consider here a pure Contourite Depositional System (CDS) and follow Gruetzner et al (2012) 15 in interpreting M as a large asymmetric mounded drift, because it meets criteria listed in Hernández-Molina et al (2008) 36 . The drift resembles modern drifts offshore of South Africa 37 or along the Mozambique Channel 11 . The M feature also resembles other, coeval, buried asymmetric mounded drifts found further south along the Patagonian margin 18 .…”

“…3A). This could represent more energetic secondary oceanographic processes (e.g., internal waves/tides) along the deeper AABW/CDW interface 11,32 . Deposition in P and M as well as minor aggradation in C reflect periods when the AABW was less energetic.…”

“…They generate a range of depositional (drifts), erosional (channels), or mixed features referred to as ‘contourites’, which typically appear in margin-parallel orientations, and together form a ‘Contourite Depositional System’ (CDS) 10 . Asymmetric mounded drifts, classified as giant, elongated drifts 6 , 9 commonly appear in slope-adjacent and open marine environments but these features and the mechanisms that form them remain poorly understood 11 . The Argentine continental rise hosts an extensive, buried CDS with a large asymmetric mounded drift that shows remarkable upslope migration.…”

Sedimentary evolution and effects of structural controls on the development of the Zambezi mixed turbidite-contourite system (Mozambique Channel, Southwest Indian Ocean) since the Oligocene

“…The U1 channel-levee complex, which was deposited during the Oligocene, is coeval to the building of the Zambezi giant 1.8 stwt-thick contourite drift on the southern bank of the upper Zambezi Valley (Fig 1B , 20A) (Raisson et al, 2016;Ponte, 2018;Thiéblemont et al, 2020).…”