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
|Author(s)||Gay Aurelien1, Padron C.2, 3, Meyer S.1, 4, Beaufort D.5, Oliot E.1, Lallemand S.1, Marcaillou B.4, Philippon M.1, Cornée J‐j.1, Audemard F.6, Lebrun J‐f.1, Klingelhoefer Frauke3, Mercier De Lepinay B.4, Münch P.1, Garrocq C.1, Boucard M.1, 4, Schenini L.4, The Garanti Cruise Team|
|Affiliation(s)||1 : Géosciences Montpellier CNRS Université de Montpellier, Université des Antilles, Place Eugène Bataillon,34095 Montpellier, France
2 : Departamento de Ciencias de la Tierra, Universidad Simón Bolívar (USB), Caracas, Venezuela
3 : Géosciences Marines, Ifremer, ZI de la Pointe du Diable CS 1007029280 Plouzané, France
4 : Géoazur, Université Côte d’Azur CNRS IRD Observatoire de la Côte d’Azur Géoazur250 Avenue Albert Einstein 06560 Valbonne, France
5 : Université de Poitiers, IC2MP ‐ UMR 7285 ‐ CNRSRue Michel Brunet F‐86073Poitiers cedex 9, France
6 : Universidad Nacional de San Luis, San Luis, Argentina
|Source||Geochemistry Geophysics Geosystems (1525-2027) (American Geophysical Union (AGU)), 2021-12 , Vol. 22 , N. 12 , P. e2021GC009809 (21p.)|
|WOS© Times Cited||4|
|Note||This article also appears in: A Fresh Look at the Caribbean Plate Geosystems|
|Keyword(s)||polygonal faults, seabed polygons, fluid seep, volumetric contraction, creep deformation|
Based on 2D seismic profiles, multibeam and seabed grab cores acquired during the Garanti cruise in 2017, 1-5 km wide seabed giant polygons were identified in the Grenada basin, covering a total area of ∼55000 km2, which is the largest area of outcropping polygonal faults (PF) ever found on Earth so far. They represent the top part of an active 700-1200 m thick underlying polygonal fault system (PFS) formed due to the volumetric contraction of clay- and smectite-rich sediments, initiated in the sub-surface at the transition between the Early to Middle Pliocene. The short axes of the best-fit ellipses obtained from a graphical centre-to-centre method were interpreted as the local orientation of a preferential contraction perpendicular to the creep deformation of slope sediments.
In the North Grenada Basin, the polygons are relatively regular, but their short axes seem to be parallel to a N40°E extension recently evidenced in the forearc, possibly extending in the backarc, but not shown in the study area. They are most probably related to a progressive burial due to a homogeneous subsidence. In the South Grenada Basin, the polygons are more elongated and their axes are progressively rotating southeastward towards the depocenter, indicating a creep deformation towards the center of the basin created by a differential subsidence. Seabed polygons and underlying PF could thus be indicative of the deformation regime of shallow sediments related to main slopes controlled by two different basin architectures.