Geomorphology of a modern carbonate slope system and associated sedimentary processes: Example of the giant Great Abaco Canyon, Bahamas

Abstract

The large acoustic data set acquired during the Carambar cruises is composed of high resolution bathymetry, backscatter data and very-high resolution seismic lines which allow for an overview of the morphology and sediment transfer processes from the shallow upper slope to the abyssal plain of a modern carbonate system: the northeastern slope of the Little Bahama Bank. Surficial distribution of the acoustic facies and echofacies reflects a wide variety of sedimentary processes along and across the slope. The western sector of the Little Bahama Bank is dominated by depositional processes whereas its eastern sector, which is incised in the lower slope by giant canyons, is affected by erosion and bypass processes. Datasets suggest that currents play an important role both in along-slope sedimentary processes and in the abyssal plain. The Antilles Current appears to affect a large part of the middle and lower slopes. The absence of sizeable present-day channel/lev ee complexes or lobes at the mouth of the canyonrevealed by the bathymetric mapindicates that the southward flowing Deep Western Boundary Current influences modern abyssal sediment deposition. Based on depositional processes and indicators of canyon maturity observed in facies distribution, the current study proposes that differential subsidence affects the eastern versus western part of the bank. The morphology of the Great Abaco Canyon and Little Abaco Canyon, which extend parallel to the platform, and the Little Bahama Bank slope appears to be related to the Great Abaco Fracture Zone.

Shape‐dependent settling velocity of skeletal carbonate grains: Implications for calciturbidites

“…As a result, margin-parallel carbonate factories may develop laterally-extensive sediment aprons containing channels, lobes and sheets (Colacicchi & Baldanza, 1986;Mullins & Cook, 1986;Playton et al, 2010). However, channel-levée systems and fans, as characteristic for siliciclastic shelf slopes, also occur in carbonate settings (Mulder et al, 2018;Recouvreur et al, 2021), although they seem to be the exception (Mulder et al, 2014). The nature of carbonate grains is in large part determined by the carbonate factory (Schlager, 2000(Schlager, , 2003Reijmer, 2021).…”

Submarine Channel Mouth Settings: Processes, Geomorphology, and Deposits

“…Similarly, carbonate depositional systems of the Bahamas contain plunge pools aligned at the base of steep (2-20 °) escarpments, where they are separated by small ridges and followed down-slope by sediment wave fields (Schnyder et al, 2018). Plunge pool depressions have been interpreted along siliciclastic submarine canyons associated with steep knickpoints within canyon thalwegs (e.g., Gamberi and Marani, 2007;Paull et al, 2011;Harris et al, 2014), and plunge pools along wide carbonate canyons occur downstream from chutes (knickpoints with hundreds of metres of relief, c. f., Mulder et al, 2019;Recouvreur et al, 2021). In the central equatorial Pacific, plunge pools ~100-m-deep were recently documented where channels cross steep (5-11 °) gradients and transition into sediment wave fields (Gardner et al, 2020).…”

“…Carbonate lobes can occur at the base of slope, though often with the influence of contour currents (e.g., Mulder et al, 2012;Reijmer et al, 2015). In some cases, the lack of carbonate lobe deposition is linked to current activity (e.g., Recouvreur et al, 2021). Carbonate basin floor settings tend to be drifts instead of lobes (Reijmer et al, 2015), which may be one contributing factor to why carbonate channel mouth examples are less prevalent than siliciclastic examples.…”

Can Offshore Meteoric Groundwater Generate Mechanical Instabilities in Passive Continental Margins?

“…However, it is in these settings that OMG is likely a major player in creating mechanical instabilities. The heads of blind submarine canyons in the Little Bahama Bank, for example, are located at water depths of ∼450 m, and these are thought to have been initiated by slope failures associated with sediment overloading (Mulder, Ducassou, Gillet, et al., 2012; Recouvreur et al., 2021; Tournadour et al., 2017). Several examples of the latter are observed along the middle slope of the Little Bahama Bank, with pockmarks located above the slide scars (Principaud et al., 2015).…”