Quantification des flux sédimentaires et de la subsidence du bassin ...

tel-00790852, version 1 - 21 Feb 2013
sediments. A minor reactivation has been detected on the inner shelf that induces a
localised deformation of Pliocene-Quaternary sedimentary cover. The amplitude of this
deformation is small, but can induce a shift of up to 50 m in the Pliocene series. It is
superimposed on deeper faults that seem to have been reactivated at around 1 Ma. The
quantification of Pliocene-Quaternary subsidence also enabled to evaluate isostatic
rebound on the outer shelf during the messinian crisis (up to 1.3 km uplift at the
Herault-Sète canyon heads).
When using older sedimentary marker from the deep-sea (the base of salt deposits,
dated at 5.6 Ma) to estimate the subsidence rate on ECORS profile, we also find a
seaward tilting subsidence of the slope with a measured angle of 1.44°. The subsidence
increases up to 996 m/Ma at 200 Km from the coast. From this point to the deepest part
of the basin, the total subsidence is then almost vertical and reaches 1070 m/Ma during
the last 5.6 Ma in the deepest part of the basin.
These very high total subsidence rates enable high sedimentation rates along the margin,
which in turn enabled the detailed record of climate evolution during Pliocene-
Quaternary that make of the Gulf of Lion a unique archive.
Abstract: (452 words). Main Text : 4578 words ; 13 Figures.
* Corresponding author and requests for materials should be addressed to Marina Rabineau
(e-mail: marina.rabineau@univ-brest.fr) Tel: (33) (0)2 98 49 87 28 Fax: (33) (0)2 98 49 87 60
Keywords : Subsidence, Passive margins, Sedimentary record, Isostasy, Pliocene-Quaternary,
Gulf of Lion, Gulf of Lions, Mediterranean Sea, Stratigraphic modelling.
1. Introduction : A rapid overview of Subsidence studies in the Gulf of Lion
Subsidence studies in the Gulf of Lion margin (Fig. 1) have recently been summarized in
Bache, 2008 ; Bache et al., 2010. We provide here only a short summary. Subsidence has long
been considered as an Atlantic-type passive margin with a general and regular seaward tilt of
the shelf (Le Pichon et al., 1971; Watts & Ryan (1976) ; Ryan, 1976; Biju-Duval, Letouzey et
al., 1978; Montadert, Letouzey et al., 1978 ; Steckler and Watts, 1980, Burrus, 1989). While
uniform extension models (McKenzie, 1978) were largely used to explain the evolution of
such margins, many discrepancies with the predictions of these models have been highlighted