Deep structure of the Demerara Plateau: From a volcanic margin to a Transform Marginal Plateau

Type Article
Date 2021-03
Language English
Author(s) Museur Thomas1, 2, Graindorge David2, Klingelhoefer FraukeORCID1, Roest WalterORCID1, Basile C.3, Loncke L.4, Sapin F.5
Affiliation(s) 1 : Ifremer, Centre de Brest, Institut Carnot – Ifremer EDROME, UR Géosciences Marines, BP 70, 29280 Plouzané, France
2 : Univ Brest, Cnrs, Géosciences Océan, UMR6538, F-29280 PLOUZANE, France
3 : ISTerre, UMR-CNRS 5275, Observatoire des Sciences de l'Univers de Grenoble, Université Joseph Fourier, Maison des Géosciences, 1381 rue de la Piscine, 38400 St. Martin d'Hères, France
4 : University of Perpignan Via Domitia, Centre de Formation et de Recherche sur les Environnements Méditerranéens (CEFREM), UMR 5110, 52 Avenue Paul Alduy, 66100 Perpignan, France
5 : Total SA, Centre Scientifique et Technique Jean Feger (CSTJF), Avenue Larribau, 64018 Pau, France
Source Tectonophysics (0040-1951) (Elsevier BV), 2021-03 , Vol. 803 , P. 228645 (22p.)
DOI 10.1016/j.tecto.2020.228645
WOS© Times Cited 11

The Demerara Plateau (offshore Suriname and French Guiana) is located at the junction of the Jurassic Central Atlantic and the Cretaceous Equatorial Atlantic Oceans. The study of its crustal structure is fundamental to understanding its tectonic history, its relationship with the adjacent oceanic domains and to enlightening the formation of Transform Marginal Plateaus (TMPs). This study presents two wide-angle seismic velocity models from the MARGATS cruise seismic experiment, and adjacent composite seismic reflexion lines. The plateau itself is characterized by a 30 km thick crust, subdivided into three layers, including a high velocity lower crust (HVLC). The velocities and velocity gradients do not fit values of typical continental crust but could fit with volcanic margin or Large Igneous Province (LIP) type crusts. We propose that the, possibly continental, lower crust is intruded by magmatic material and that the upper crustal layer is likely composed of extrusive volcanic rocks of the same magmatic origin, forming thick seaward dipping reflector sequences tilted to the west. This SDR complex was emplaced during hotspot related volcanic rifting preceding the Jurassic opening of the Central North Atlantic and forming the present-day western margin of the plateau. The internal limit of the SDR complex corresponds to the future limit of the eastern margin. The Demerara Plateau would therefore be an inherited Jurassic volcanic margin boarding the Central Atlantic. This margin was reworked during the Cretaceous at the eastern limit of the Jurassic SDR complex, creating the present-day northern transform margin and the eastern divergent margin along the Equatorial Atlantic. This study also highlights the major contribution of thermal anomalies such as hotspots and superposed tectonic phases in the history of TMPs, which share a great number of characteristics with Demerara.

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