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

tel-00790852, version 1 - 21 Feb 2013
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corresponds to the deposition of detritals in relation with intensive subaerial erosion
immediately after the fast Messinian major sea-level drawdown; step II (?-5.46 Ma) is
characterised by deposition of evaporites (more than 2 kilometers in thickness) since the sea-
level drawdown and during a slow sea-level rise resulting in landward migration of the
shoreline; step III is the instantaneous catastrophic reflooding of the Mediterranean at 5.46
Ma.
This scenario, the first to be expressed for the peak of the MSC, has been numerically
modelled for the Western Mediterranean and the expected thickness of evaporites implies that
precipitation minus evaporation (E-P) was higher than today when the basin was dried up.
Because of similar observations, this scenario should be expandable to the whole
Mediterranean. The missing pieces for continuing to improve the understanding of the peak of
the MSC at the scale of the whole Mediterranean are ground-truth observations of the pre-
evaporite geometries as well as an accurate datation of the corresponding sediments.
Recognition at larger scale of the critical stratigraphic markers identified in the Gulf of Lions
in other Mediterranean basins should allow:
1/ a finer chronostratigraphic constraint of the MSC leading to comparisons between different
basins. In particular, the understanding of the connections between Western and Eastern
Mediterranean and the role of sill that probably separated these basins is necessary to model
the MSC for the whole Mediterranean (Bache et al., 2012; Gargani et al., 2008; Gargani and
Rigollet, 2007; Leever et al., 2011; Leever et al., 2010);
2/ the quantification of vertical movements across the whole Mediterranean that will lead to
better understanding of the behaviour of the lithosphere (its rigidity) in response to rapid
variations of load during the MSC (sedimentary transfers, sea-level variations).
New data acquisition (geophysical and sampling) is needed in the central basins to provide
accurate dating of the Messinian events, for example in drilling the pre-salt sedimentary
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