Paleogene V‐Shaped Basins and Neogene Subsidence of the Northern Lesser Antilles Forearc

Abstract

Worldwide, forearc trench-perpendicular basins are interpreted as the result of trench-parallel extension possibly due to either strain partitioning as at the Aleutians (Ryan & Scholl, 1989) and Ryukyu (Nakamura, 2004) Subduction Zones, and/or to increasing margin curvature as at the Marianas (Heeszel et al., 2008) and Hellenic trenches (Angelier, 1978; Mascle & Martin, 1990). In more extreme cases, widespread deformation of forearc domains results from the collision of buoyant crustal features (e.g., oceanic plateaus, seamount chains, or continental fragments) which is prone to generate bending and rotation of subduction zones (e.g., Vogt et al., 1976). Strongly curved convergent plate boundaries are subject to alongstrike variations in subduction obliquity and thus commonly associated with large-scale rigid body rotation

Elongated Giant Seabed Polygons and Underlying Polygonal Faults as Indicators of the Creep Deformation of Pliocene to Recent Sediments in the Grenada Basin, Caribbean Sea

“…The N40°E orientation evidenced from polygon shapes thus may indicate that the PF in the upper sedimentary cover (unit U3 at least) have recorded such extension in the backarc. This is possibly explained by thermal relaxation related to the cessation of arc activity in the northeastern LAA (Jany et al, 1990;MacPhee et al, 1989; and/or possibly by tectonics influence of subduction dynamics (Boucard et al, 2021;. However, the more recent and continuous subsidence since Late Miocene-Early Pliocene can explain shallower depths of both the present-day seafloor and the base of unit U3, with an average depth of 2 s TWT (Figure 9a), and a constant thickness of unit U3 of about 0.7-0.8 s TWT, indicating a homogeneous subsidence in the entire area with no major slope orientation except in the vicinity of emerged volcanic islands and around Saba Bank (Figure 9b).…”

Evolution of a Shallow Volcanic Arc Pluton During Arc Migration: A Tectono‐Thermal Integrated Study of the St. Martin Granodiorites (Northern Lesser Antilles)

“…Indeed, new geochronometric data suggest a slow westward arc migration through time (Legendre et al, 2018). Because of intraplate deformation, and contemporaneously with the migration of the volcanic arc, the northern Lesser Antilles forearc was segmented into deep V-shaped basins and highs (Boucard et al, 2021). These highs expose various crustal levels of the Eocene-lowermost Miocene arc: from its roots intruding Eocene marine deposits in St. Martin and St. Barthélemy, to its surface deposits in Antigua (e.g., Andréïeff et al, 1988;Cornée et al, 2020;Legendre et al, 2018;Westercamp & Andréïeff, 1983).…”

“…To the north, the Anguilla bank is bounded by the Anegada Trough, a transtensive deep basin trending parallel to the V-Shaped basins, which crosscuts the Lesser Antillean forearc. These N40° trending structures are thought to accommodate strain in the upper plate since the late Oligocene-early Miocene (Boucard et al, 2021;Chaytor & ten Brink, 2015;Jany et al, 1990;Laurencin et al, 2017).…”

“…It has been proposed that tilting of the Eocene volcanic series is related to a regional-scale deformation event that occurred before the Oligocene (Andréïeff et al, 1988;Legendre et al, 2018;Westercamp & Andréïeff, 1983). The Bluff fault, responsible for the main vertical motion (and tilting) in St. Martin, trends N45°, parallel to the main crustal faults bounding the V-Shaped basins, and the timing of its activity is similar and postdate the opening of the Anegada Trough (Boucard et al, 2021). Similar N45° trending faults exist in the neighboring island of St. Barthélemy (south of St. Martin, Legendre et al, 2018 and reference therein).…”

“…In addition to tectonic control of the subsidence, we propose that when the magmatic activity stopped in the present-day forearc and began to migrate (or jump, towards the west, the crust cooled down as illustrated in Figure 11 and consequently gained in density (or lost its buoyancy), which may have triggered subsidence. Indeed, recent findings (Boucard et al, 2021;Cornée et al, 2021), show that the migration of the Lesser Antilles arc is accompanied by regional drowning of the Anguilla bank from 15 to ∼5 Ma. Moreover, we demonstrate that in St. Martin the magmatic emplacement is contemporaneous with extension and exhumation (Figure 12).…”