Contourite depositional systems along the Mozambique channel: The interplay between bottom currents and sedimentary processes

Abstract

We present a combined study of the geomorphology, sedimentology, and physical oceanography of the Mozambique Channel to evaluate the role of bottom currents in shaping the Mozambican continental margin and adjacent Durban basin. Analysis of 2D multichannel seismic reflection profiles and bathymetric features revealed major contourite deposits with erosive (abraded surfaces, contourite channels, moats, furrows and scours), depositional (plastered and elongated-mounded drifts, sedimentary waves), and mixed (terraces) features, which were then used to construct a morphosedimentary map of the study area. Hydrographic data and hydrodynamic modelling provide new insights into the distribution of water masses, bottom current circulation and associated processes (e.g., eddies, internal waves, etc.) occurring along the Mozambican slope, base-of-slope and basin floor. Results from this work represent a novel deep-sea sedimentation model for the Mozambican continental margin and adjacent Durban basin. This model shows 1) how bottom circulation of water masses and associated sedimentary processes shape the continental margin, 2) how interface positions of watermasses with contrasting densities (i.e., internal waves) sculpt terraces along the slope at a regional scale, and 3) how morphologic obstacles (seamounts, Mozambique Ridge, etc.) play an essential role in local water mass behaviours and dynamics. Further analysis of similar areas can expand understanding of the global role of bottom currents in deep-sea sedimentation. Highlights► Combined study of the geomorphology, sedimentology, and physical oceanography of the Mozambique Channel. ► Bottom circulation of water masses and associated sedimentary processes shape the continental margin. ► Interface positions of water-masses with contrasting densities (i.e., internal waves) sculpt terraces along the slope at a regional scale. ► Morphologic obstacles play an essential role in local water mass behaviours and dynamics.

Crustal structure of the East African Limpopo margin, a strike-slip rifted corridor along the continental Mozambique Coastal Plain and North Natal Valley

“…Velocity models built from these data challenge the tight-fit scenario as they unravel the continuity of a thick and highly intruded continental crust beneath the MCP and NNV (Moulin et al, 2020;Leprêtre et al, 2021;Watremez et al, 2021). Conversely, these results strengthen previous studies that interpreted continental crust in the area (Domingues et al, 2016;Hanyu et al, 2017) and brings strong support for a "loose" fit plate reconstruction without plate overlap (Thompson et al, 2019). Within such a framework, both rifting and subsequent spreading are inferred to proceed from a continuous quasi N-S movement of the Antarctica-Australia and Madagascar-India plates with respect to Africa with major implications for the dynamics of rifting along the East African margins and the age of Gondwana breakup.…”

Hybrid turbidite-drift channel complexes: An integrated multiscale model

“…2E). These currents are likely related to the East African Coastal Current (moorings B and D) and deeper Antarctic Intermediate Water (Schouten et al, 2003;van Aken et al, 2004;Thiéblemont et al, 2019). Annual variation in current strength may relate to the seasonal occurrence of eddies along the Mozambique Channel (de Ruijter et al, 2002;Nauw et al, 2008;Miramontes, et al, 2019;Thiéblemont et al, 2019).…”

“…While the influence of bottom currents on submarine channel architecture has been recognized, interpretation has been hampered by a lack of direct monitoring data (Shanmugam et al, 1993;Gong et al, 2018;Sansom, 2018;Fonnesu et al, 2020). Modern, integrated data sets, including direct measurements and monitoring of bottom currents, are of great importance in understanding the complexity of oceanographic processes (Fierens et al, 2019;Miramontes et al, 2019;Thiéblemont et al, 2019), sediment gravity flows (Clare et al, 2016;Azpiroz-Zabala et al, 2017;Symons et al, 2017), and the preservation of strata within submarine channel complexes (Gamberi et al, 2013;Vendettuoli et al, 2019). This study combines an integrated subsurface study (three-dimensional [3-D] seismic, core, and well-log data) with modern seafloor geomorphology and near-bed bottom-current measurements to develop a process-product-based sedimentological model for bottom currentinfluenced submarine channel complexes.…”

The erosive power of the Malvinas Current: Influence of bottom currents on morpho-sedimentary features along the northern Argentine margin (SW Atlantic Ocean)

“…We suggest that contourite terraces may have been initiated by erosion on the slope generated by the action of two water masses and their interphase trough time, being the (paleo) Malvinas Current one of the key factors that progressively cut the slope landwards, widening the contourite terrace with time. The fact that the Argentine contourite terraces are much wider and flatter than other terraces observed for instance in the Mediterranean Sea (Ercilla et al, 2016;Miramontes et al, 2019), along the Mozambican margin (Thiéblemont et al, 2019;Miramontes et al, 2020) and in the Makassar Strait (Brackenridge et al, 2020) could be related to the higher speed of near-bottom currents as part of the Malvinas Current and the long time period of erosion (since the opening of the Drake Passage). The particular flat morphology with an abrupt edge of the terraces along the Argentine margin may favour the formation of internal waves at the terrace edge, similar to those observed at the shelf break (Jackson et al, 2012), that could also favour sediment transport and erosion along the terrace.…”

“…Terrace is deeper (~500 m) south of the MdP Canyon compared to the north where it is located at shallower depth (~400 m) (Preu et al, 2013). Contourite terraces can show depositional and erosional features and often correspond to the landward upper part of plastered drifts (Hernández-Molina et al, 2016a;Thiéblemont et al, 2019;Miramontes et al, 2021). The…”