Coexistence of Adjacent Siliciclastic, Carbonate, and Mixed Sedimentary Systems: An Example From Seafloor Morphology in the Northern Lesser Antilles Forearc

Abstract

Three main types of factors commonly control the nature of the clasts, the arrangement of the distinctive lithologies, and the general architecture of turbidite systems: sedimentation rate and carbonate production; climates and glacio-eustatism; and morphology and tectonics. The coexistence of adjacent systems of distinctive nature is, however, scarcely documented, and the relative influence of each factor needs better constrain. In the Northern Lesser Antilles Segment (NLAS), carbonate and siliciclastic sediment sources coexist within a 150 km lateral distance, with carbonate platforms lying onto a volcanic substratum, and by a succession of spurs and triangular valleys that are bounded by active normal faulting. To better understand the factors controlling sedimentary processes from the carbonate platform sources to the deep-sea sinks, we used backscatter, bathymetry, multichannel seismic, and sub-bottom profiles. Sedimentary systems are dominated by siliciclastic input (by retrogressive erosion of confined canyons affecting the volcanic slope), carbonate input (by carbonate sediment transported by oceanic- and wind-driven submarine currents beyond the leeward edges of carbonates platforms), or both. In the mixed systems, the retrogressive erosion of the canyon head determines the nature of the source (volcanic on the slope, carbonate when the canyons reach the shelf edge). Glacio-eustatism has a key role in carbonate availability on the platform, as attested by the presence of drowned platforms. The main contribution of this study is the identification of the major role that tectonic activity plays in the short-distance coexistence of the distinctive sedimentary systems since fault-bounded V-shaped valleys in map view offer alternating leeward and windward edges favoring carbonate or mixed systems. Additionally, the steep slope gradient induced by normal faults and regional subsidence seems to be the main factor controlling sediment dispersal. It causes multiple line sources and the dispersion of gravity-driven currents under the effect of hydraulic jumps, thus preventing the formation of a channelized system. Our study provides a modern analog of adjacent systems dominated by distinctive lithologies in a tectonically active area. The results appear particularly appropriate to decipher the nature of ancient source-to-sink systems dominated by complex tectonics, paleo-bathymetry, and sediment routings.

Submarine paleoseismology in the Japan Trench of northeastern Japan: turbidite stratigraphy and sedimentology using paleomagnetic and rock magnetic analyses

“…A suspension cloud caused by a flow rebound in a confined basin has been considered for forming the thick muddy interval (e.g., Patacci et al 2015). The oscillating currents and seiche effects in confined basins have also been proposed by McHugh et al (2016McHugh et al ( ), Çağatay et al (2012 and Yakupoğlu et al (2022) for Marmara Sea, and it has been recognized in other basins such as the Canal du Sud in Haiti (e.g., ) and most recently in the Lesser Antilles forearc basins (Morena et al 2022). The seiche effects generated by earthquakes are considered to induce a massive structureless characteristic of "homogenite. "…”

Sedimentary Records in the Lesser Antilles Fore‐Arc Basins Provide Evidence of Large Late Quaternary Megathrust Earthquakes

“…The crustal shallow earthquakes occur on two sets of active normal faults that accommodate the oblique convergence between the North American and the Caribbean plates (Feuillet et al, 2002(Feuillet et al, , 2004(Feuillet et al, , 2010Leclerc et al, 2016): (a) A NE-SW striking system in the fore-arc domain that forms graben and half graben perpendicular to the arc between the Virgin Islands and the Guadeloupe island and (b) an arc-parallel en-échelon fault system between Saba and Martinique (Figure 1). Crustal active faulting, megathrust earthquakes, the subduction of the Barracuda and Tiburon ridges (Figure 1a), the growth of the accretionary wedge, the development of reef platforms and the volcanic processes shape the seafloor morphology at various space and time scales (Boucard et al, 2021;Feuillet et al, 2002Feuillet et al, , 2010Feuillet et al, , 2011Laigle et al, 2013;Laurencin et al, 2019;Macintyre, 1972) and exert a control on the sedimentary processes (Morena et al, 2022;Seibert et al, 2020). As expected in a mixed carbonated-siliciclastic environment along an active margin where large earthquakes, tsunamis, volcanic events and hurricanes can occur, the sediments that were cored in the Lesser Antilles in the framework of previous investigations are diverse: tephra falls, deposits from reef platform or volcanic flank instabilities, turbidites of various nature (Beck et al, 2012;Bieber et al, 2021;Brunet et al, 2016;Le Friant et al, 2008;Morena et al, 2022;Picard et al, 2006;Reid et al, 1996;Seibert et al, 2020;Trofimovs et al, 2013).…”

“…We infer that each of those was promoted by a large earthquake on a section of the megathrust located north of the Barracuda ridge maybe extending over the whole northern part of the arc (up to the Anegada Passage, Figure 11). Seven cores were taken in this area and their analysis, in progress (Morena et al, 2022), is needed to confirm this hypothesis. It is noteworthy that large pre-columbian overwashed sand deposits were found in Anegada (British Virgin Islands, Atwater et al, 2017) and in several other coastal lagoons and ponds in Anguilla and Saint Martin (Biguenet et al, 2021(Biguenet et al, , 2022.…”

“…Crustal active faulting, megathrust earthquakes, the subduction of the Barracuda and Tiburon ridges (Figure 1a), the growth of the accretionary wedge, the development of reef platforms and the volcanic processes shape the seafloor morphology at various space and time scales (Boucard et al., 2021; Feuillet et al., 2002, 2010, 2011; Laigle et al., 2013; Laurencin et al., 2019; Macintyre, 1972) and exert a control on the sedimentary processes (Morena et al., 2022; Seibert et al., 2020). As expected in a mixed carbonated‐siliciclastic environment along an active margin where large earthquakes, tsunamis, volcanic events and hurricanes can occur, the sediments that were cored in the Lesser Antilles in the framework of previous investigations are diverse: tephra falls, deposits from reef platform or volcanic flank instabilities, turbidites of various nature (Beck et al., 2012; Bieber et al., 2021; Brunet et al., 2016; Le Friant et al., 2008; Morena et al., 2022; Picard et al., 2006; Reid et al., 1996; Seibert et al., 2020; Trofimovs et al., 2013).…”