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

tel-00790852, version 1 - 21 Feb 2013
(m) and we therefore obtain a 2D section of interpretated profile LRM18 in depth (see later
in results).
On the slope and deep sea we used ESP (Expanding Spread Profiles) data that were shot along
the ECORS profile (De Voogd, 1991 #26), and that have been interpreted by Pascal et al.,
1993, and the velocities obtained by tomographic inversion from new refraction data acquired
during the Sardinia Cruise (Gailler et al., 2009) to build the 2D velocity model (Figure 6D).
We also compared those velocities with measuremets at GLP2 well (1246 m water depth, see
position on ECORS line, Figure 5) and Figure 6 TFP measurements in GLP2 showed
velocities from 1800 m/s at the top of the well to 2500 m/s at 2508 m ; 3000 m/s at 4100 m ;
3180 m/s at 4855 m (at the base on Miocene series), and 3320 m/s at 5345 m (i.e. at 4100
mbsf).
After time-depth conversion, we therefore obtain a 2D section of interpreted reflectors in
depth (m) (Figure 7 and 12).
• Dating of surfaces
Very high-resolution profiles interpreted in earlier studies (Rabineau, 2001, 2005) showed
that the last 5 erosional surfaces correspond to the last five glacial maximum erosions of
100,000 years cycles, with preservation of the shoreline on the outer shelf. The fifth surface
D30 was interpreted as MIS12.2 and therefore dated at 434 000 years (according to orbitally
tuned isotopic Specmap curve, Imbrie, 1984) (Rabineau et al. 2005, 2006). This interpretation
and dating has now been confirmed on the shelf thanks to the Promess drillsite (Bassetti et al.,
2008, Sierro et al., 2009).
The messinian margin erosional surface (MES) is generally dated at 5.33 Ma according to the
GSSP (Global Stratotype Section and Point) of the Lower Pliocene Zanclean Stage dated
astronomically by Van Couvering et al., 2000. Most authors also agreed to date the initiation
of salt deposition at 5.6 Ma, and the end of the Salinity crisis at 5.33 Ma (CIESM, 2008).
4- Data and Results : measure of subsidence rates
a- On the shelf
The high resolution erosional surface D30 was plotted on LRM18 profile (Figure 4). Below
this D30 surface, other erosional surfaces could be plotted: surface q10 corresponds to a
major erosional surface, that lies around 450 ms (or 400 m) below present day sea-level at