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G-Cubed: Geochemistry, Geophysics, Geosystems; an electronic journal of the Earth sciences

 

Keywords

  • quaternary
  • Mediterranean
  • shoreface
  • paleoclimate

Index Terms

  • Hydrology: Sedimentation
  • Global Change: Sea level change
Abstract
Cited By (0)
 

Abstract

The 100-ka and rapid sea level changes recorded by prograding shelf sand bodies in the Gulf of Lions (western Mediterranean Sea)

M. A. Bassetti

Institut de Modélisation et d'Analyse en Géo-Environnement et Santé, Université de Perpignan, 52 avenue Paul Alduy, F-66860 Perpignan, France

Géosciences Marines, Institut Français de Recherche pour l'Exploitation de la Mer, BP70, F-29280 Plouzané, France

S. Berné

Institut de Modélisation et d'Analyse en Géo-Environnement et Santé, Université de Perpignan, 52 avenue Paul Alduy, F-66860 Perpignan, France

Géosciences Marines, Institut Français de Recherche pour l'Exploitation de la Mer, BP70, F-29280 Plouzané, France

G. Jouet

Géosciences Marines, Institut Français de Recherche pour l'Exploitation de la Mer, BP70, F-29280 Plouzané, France

M. Taviani

Istituto di Scienze Marine, CNR, via Gobetti 101, I-40129 Bologna, Italy

B. Dennielou

Géosciences Marines, Institut Français de Recherche pour l'Exploitation de la Mer, BP70, F-29280 Plouzané, France

J.-A. Flores

Facultad de Ciencias, Universidad de Salamanca, Plaza Merced s/n, E-37008 Salamanca, Spain

A. Gaillot

Altran Quest, Technopole Brest Iroise, CS 23866, F-29238 Brest, CEDEX 3, France

R. Gelfort

Institut für Geowissenschaftliche Gemeinschaftsaufgaben, Stilleweg 2, D-30655 Hannover, Germany

S. Lafuerza

GRC Geociències Marines, Departament d'Estratigrafia i Paleontologia i Geociències Marines, Universitat de Barcelona, Martí i Franquès s/n, E-08028 Barcelona, Spain

N. Sultan

Géosciences Marines, Institut Français de Recherche pour l'Exploitation de la Mer, BP70, F-29280 Plouzané, France

Thick forced regressive units on the wide continental shelf of the Gulf of Lions (western Mediterranean) recorded the composite effect of sea level changes during the Quaternary. They are mostly composed of coastal siliciclastic and bioclastic wedges showing clinoform geometry. These deposits have been intensively explored through high-resolution seismic investigations, but only recently it was possible to ground truth seismic interpretations, based on a long (100 m) borehole that crossed the succession and recovered a large part of the mainly sandy deposits (∼84% recovery). A multiproxy analysis of the sedimentary succession shows that (1) the stratal architecture of the shelf margin is defined by major bounding surfaces that are polygenic erosion surfaces associated with coarse-grained material incorporating abundant and diverse shells, including cold-water fauna (presently absent from the Mediterranean Sea). Between each surface, coarsening upward units with steep (up to 5°) foresets are made of massive (more than 20 m thick) sands with possible swaley and hummocky cross-stratification, passing seaward to sands with muddy intervals and, further offshore, alternating highly boiturbated sands and silts. Each prograding wedge corresponds to a forced-regressive shoreface (or delta front/prodelta), deposited during the overall sea level falls occurring at (relatively slow) interglacial/glacial transition and therefore represents the record of 100 ka cyclicity. Higher-frequency Milankovitch cyclicities are also probably represented by distinct shoreface/delta front wedges; (2) detailed examination of the architecture and chronostratigraphy of the most recent sequence shows that minor bounding surfaces, corresponding to abrupt shallowing of sedimentary facies, separate downward stepping parasequences within the last 100 ka sequence. These events are in phase with millennial-scale glacial climatic and sea level variability, the downward shift surfaces corresponding to the falls during the coldest stadials. These deposits provide a comprehensive and well-constrained Pleistocene analog to the numerous shoreface deposits attributed to falling-stage systems tracts recognized in ancient stratigraphic records, studied at the outcrop scale.

Received 12 October 2007; accepted 10 September 2008; published 13 November 2008.

Citation: Bassetti, M. A., S. Berné, G. Jouet, M. Taviani, B. Dennielou, J.-A. Flores, A. Gaillot, R. Gelfort, S. Lafuerza, and N. Sultan (2008), The 100-ka and rapid sea level changes recorded by prograding shelf sand bodies in the Gulf of Lions (western Mediterranean Sea), Geochem. Geophys. Geosyst., 9, Q11R05, doi:10.1029/2007GC001854.

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