Quaternary coral reef complexes as powerful markers of long-term subsidence related to deep processes at subduction zones: Insights from Les Saintes (Guadeloupe, French West Indies)

Abstract

Geodetic measurements reveal modern rates of tectonic deformation along subduction zones, but the kinematics of long-term deformation are typically poorly constrained. We explore the use of submarine coral reefs as a record of long-term coastal vertical motion in order to determine deformation rate and discuss its origins. The Lesser Antilles arc results from the subduction of the American plates beneath the Caribbean plate and undergoes regional vertical deformation. Uplifted reefs along forearc islands are markers of the interplay between tectonics and sea-level variations since the late Pleistocene. We compared results from a numerical model of reef-island profile development to high-resolution marine geophysical measurements of Les Saintes reef plateau (Guadeloupe, French West Indies), a ∼20-km-wide, 250-m-thick submerged platform that lies at 45 m below sea level along the volcanic arc, to constrain its vertical deformation history. Models explore different scenarios over wide parameter domains including start time, basement morphology, sea level variations, reef growth rate, subaerial erosion rate, and vertical motion history. The major features of the plateau (its depth, internal structure, unusual double-barrier) is only reproduced in a context of subsidence, with a constant rate of −0.3 to −0.45 mm/yr since the late Pleistocene, or in a context of increasing subsidence, presently of ∼–0.2 mm/yr. Discussed in the framework of the forearc vertical deformation history, this result indicates subsidence is promoted by local faulting, volcanic, and deep subduction processes. Coseismic deformation accumulation could be a mechanism by which deformation builds up in the long-term. We show that subduction can drive long-term subsidence of a volcanic arc, and demonstrate that submarine reefs are powerful markers of long-term vertical motion.

Estimation of Lesser Antilles Vertical Velocity Fields Using a GNSS-PPP Software Comparison

“…Some vertical movement assessments in this area were performed in the past. Paleo-geodesy based on coral reef growth tends to show a subsidence trend in Martinique and Les Saintes Islands (south of Guadeloupe archipelago) (Weil-Accardo et al 2016;Leclerc and Feuillet 2019). This subsidence is corroborated by GNSS observations for a few stations within the vertical velocity ULR6 solution (Santamaría-Gómez et al 2017).…”

The polygenetic Kahouanne Seamounts in the northern Lesser Antilles island arc: Evidence for large-scale volcanic island subsidence

“…Although the closest of these study sites is about 100 km from the Kahouanne Seamounts, the fact that similar subsidence rates are observed between Guadeloupe and Martinique (separated by 170 km) suggests that regional subsidence is indeed impacting a large area of the northern Lesser Antilles, as suggested by Leclerc et al (2015). A detailed analysis of submerged coral reef complexes from Les Saintes (Guadeloupe) by Leclerc and Feuillet (2019) indicated that their configurations and present depths could only be explained by subsidence and not by westward tilting of the arc platform as evidenced by uplifted carbonate terraces in Grand Terre, Marie Galante and La Desirade. They considered a number of possible mechanisms to explain subsidence of the carbonate platforms including the influence of volcanic activity (magma chamber cooling, loading of volcanic edifices, changes in hydro-static pressures of deep magma chambers), active faulting, and long-term subduction processes.…”

“…Recent studies of drowned carbonate platforms off the islands of Guadeloupe and Martinique have revealed evidence for tectonic Distance (meters) Depth (meters below sealevel) subsidence with rates from 300 to 400 m/My, influenced by regional as well as local processes (Leclerc et al, 2014(Leclerc et al, , 2015Leclerc and Feuillet, 2019). Although the closest of these study sites is about 100 km from the Kahouanne Seamounts, the fact that similar subsidence rates are observed between Guadeloupe and Martinique (separated by 170 km) suggests that regional subsidence is indeed impacting a large area of the northern Lesser Antilles, as suggested by Leclerc et al (2015).…”

“…Leclerc et al, 2014Leclerc et al, , 2015. There is also evidence for localized uplift along the arc (Leclerc and Feuillet, 2019) including on Montserrat, notably at Roche's Bluff (Harford et al, 2002) The Kahouanne Seamounts lie about 25 km southeast of the island of Montserrat at the eastern side of an asymmetrical graben (Kahouanne Valley), oriented in a NW-SE direction and with greater throw along the western side (LeBas et al, 2011, Fig. 1).…”

“…Subsidence rates in intra-arc basins are likely to be high and can impact both the distribution and evolution of nearby volcanic centers (Yamaji, 1990;Clift and ODP Leg 135 Scientific Party, 1994). In addition, there may be wider scale regional subsidence in rifted arcs related to a variety of possible factors including extension itself, cooling in the forearc, changes in subduction plate coupling, changes in density of the active arc crust related to igneous differentiation and volcanism, and coseismic deformations associated with megathrust earthquakes (Leclerc and Feuillet, 2019). In the northern Lesser Antilles, there is evidence for the subsidence of marginal reefs surrounding Guadeloupe and Martinique, at rates of decimeters per thousand years (e.g.…”