Late Quaternary geomorphology and sedimentary processes in the Zambezi turbidite system (Mozambique Channel)

Abstract

The morphology and present-day sediment distribution of the Zambezi turbidite system was investigated using new bathymetric and sub-bottom profiler data as part of the PAMELA research project. The Zambezi turbidite system is composed of two depositional systems: a channelized fan (the Zambezi Fan) and a semi-confined fan (in the lntermediate Basin). The Zambezi Fan includes the Zambezi Valley, which is deeply incised in the Mozambique Channel and is more than three times as large and deep as the great Tanzanian and North Atlantic Mid-Ocean channels. The erosion in the Zambezi Valley is evidenced by its V-shaped morphology and the existence of a U-shaped thalweg affected by several generations of incisions. Based on echo facies and cores from literature, sediments of the Zambezi Fan are dominantly coarse-grained and fine-grained overbank deposits are infrequent. The distal portion of the Zambezi Fan is a main depositional area where typical transparent wedged-shape seismic bodies are interpreted as terminal lobes. Seismic facies in the Intermediate Basin are thought to represent mostly fine-grained turbidites intercalated with infrequent coarse-grained sheet-like turbidites. Hydrodynamic circulation (from surface eddies to the deep circulation of NADW) appears to have a great impact on the Mozambique Channel sedimentation and is suggested (1) to be involved in the delivery of the Zambezi River sediments along the Mozambique margin, (2) to entrain the upper suspended load of turbidity currents, contributing to the absence of fine-grained sedimentation and (3) to contribute to the erosion of the valley flanks leading to the exceptionally great dimensions of the valley. Highlights ► The Zambezi turbidite system comprises a channelized fan and a semi-confined fan. ► The Zambezi Valley has an atypical morphology compared to other turbidite systems. ► Erosional processes dominate in the valley. ► From echo facies, deposition appears mainly fine-grained in the semiconfined fan. ► Oceanic and turbidity currents control sediment distribution and erosion.

On the termination of deep-sea fan channels: Examples from the Rhône Fan (Gulf of Lion, Western Mediterranean Sea)

“…Channels disconnected from the main channel, also called "headless" are common features and occur at shallow and deep-water, in small and big sedimentary systems like on prodeltas (Gales et al, 2019), in fjords (Heijnen et al, 2020), in lakes (Girardclos et al, 2012) and on deep, basin wide, turbidite systems (Fierens et al, 2019). Here we discuss their inception together with the related topic of channel sinuosity that are thoroughly addressed in scientific publications (Peakall et al, 2000).…”

Fluid seepage associated with slope destabilization along the Zambezi margin (Mozambique)

“…Nowadays, the Zambezi turbidite system is disconnected from the Zambezi river system (Schulz et al, 2011;Fierens et al, 2019;Miramontes et al, 2019). The sediments are dispersed by strong NNE-SSW trending coastal currents on the continental shelf (Schulz et al, 2011;Wiles et al, 2017a and b).…”

Hybrid turbidite-drift channel complexes: An integrated multiscale model

“…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.…”