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. (25th November 2021)

• Record Type: Journal Article
• Authors: Gay, A.; Padron, C.; Meyer, S.; Beaufort, D.; Oliot, E.; Lallemand, S.; Marcaillou, B.; Philippon, M.; Cornée, J‐J.; Audemard, F.; Lebrun, J‐F.; Klingelhoefer, F.; Mercier de Lepinay, B.; Münch, P.; Garrocq, C.; Boucard, M.; Schenini, L.
• Is Part Of: Geochemistry, geophysics, geosystems. Volume 22:Number 12(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-11-25
• Subjects: polygonal faults -- seabed polygons -- fluid seep -- volumetric contraction -- creep deformation; Geochemistry -- Periodicals; Geophysics -- Periodicals; Earth sciences -- Periodicals; 550.5
• DOI: 10.1029/2021GC009809
• Languages: English
• ISSNs: 1525-2027

Abstract

Abstract: 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 ∼55, 000 km 2, which is the largest area of outcropping polygonal faults (PF) ever found on Earth so far. They represent the top part of an active 700–1, 200 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 center‐to‐center 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 toward the depocenter, indicating a creep deformation toward 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. Key Points: Seabed giant polygons in the Grenada Basin cover the largest area (55, 000 km 2 ) ever found on Earth The short axis of best‐fit ellipses of polygons may represent the orientation of the creep deformation of slope sediments The north and south tectonic domains in the Grenada Basin are marked by major differences in the shape and orientation of seabed polygons