T33C-2946
Long-term deformation of the Lesser Antilles arc recorded by Late Pleistocene carbonate platforms: questioning our present knowledge of the megathrust seismic behavior.
Wednesday, 16 December 2015
Poster Hall (Moscone South)
Nathalie Feuillet1, Frédérique Leclerc2, Jennifer Weil Accardo1, Guy Cabioch3, Sara Bazin1, Francois Beauducel1, Georges Boudon1, Christine Deplus4, Pierre Deschamps5, Lyvanne De Min6, Eric Jacques1, Lebrun Jean-Frederic6, Anne Le Friant1, David Mélézan1, Anne-Sophie B Meriaux7, Marie Perret1, J Taylor Perron8, Belle Philibosian9 and Jean-Marie Marie Saurel10, (1)Institut de Physique du Globe de Paris, Paris, France, (2)Earth Observatory of Singapore, Nanyang Technological University, Singapore, Singapore, (3)Laboratoire d’océanographie et du Climat, Institut de Recherche pour le Développement, Bondy, France, (4)IPGP & CNRS, Paris Cedex 05, France, (5)CEREGE, Aix-en-Provence Cedex, France, (6)Université des Antilles, Pointe-à-Pitre, Guadeloupe, (7)Newcastle University, Newcastle Upon Tyne, United Kingdom, (8)Massachusetts Institute of Technology, Cambridge, MA, United States, (9)Columbia University of New York, Palisades, NY, United States, (10)Institut de Physique du Globe de Paris, Observatoire Volcanologique et Sismologique de Martinique, Paris, France
Abstract:
The Lesser Antilles subduction zone is relatively seismically quiet, hasn’t produced M8+ earthquake since the 19th century and recent geodetic studies indicate that it is presently weakly coupled. However, the islands of the forearc are being uplifted since at least 330 ka, at rates of several tenths of m/ka, due to subduction processes. In order to understand the long-term deformation of the Caribbean margin in this subduction context, we aimed at characterizing and quantifying the along-dip and along-strike pattern of the deformation. Through carbonate platform morphology and stratigraphy studies and modeling, offshore the volcanic arc islands of Les Saintes and Martinique, we show that these reef platforms are composed of multi-superimposed sea-level highstand deposits separated by subaerial exposure surfaces formed during sea-level low stands. This stratigraphy is typical of drowning carbonate platforms and we estimated the subsidence rate of these platforms to be of few tenths of m/ka. By summarizing the previous studies, we picture the vertical deformation pattern along and across the Lesser Antilles arc for the MIS5 highstand deposit. We discuss the different potential processes capable of driving this deformation, such as crustal faulting, volcanism and subducting ridges that have only local effects on the deformation pattern. Finally, we examine the implications of our results for the megathrust. Long-term deformations in the Lesser Antilles, but also seismic cycle-induced deformations, challenge our understanding of the megathrust seismic behavior and indicate that the state of coupling of the megathrust is most probably transient over time in order to sustain these deformation.
