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

tel-00790852, version 1 - 21 Feb 2013
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Mistral 1 this boundary, respectively located at 1540 and 1675 m depth, corresponds to a
transition from marine to littoral conditions (Fig. 5; Cravatte et al., 1974). The sediments
overlying this boundary and located below the base of Dm are dated in these wells from
Middle to Upper Miocene (Cravatte et al., 1974). In Calmar 1, the boundary is located at 1400
m and has been ascribed to the Serravallian/Tortonian transition (Fig. 5; Guennoc et al.,
2000), leading to a younger age for the deposition of Dm prisms.
4.2.2. Transgressive evaporites
The TRS identified in the Gulf of Lions highlights the existence of a slow landward migration
of the shoreline before the catastrophic reflooding of the Mediterranean (Bache et al., 2009;
Bache et al., 2012). Seismic units onlapping this surface were not clearly identified due to the
unclear seaward extent of this surface and the lack of seismic data to accurately observe this
transition. First interpretations assumed that only the Upper Evaporites (UU) and 52 m of
sandstones drilled in GLP2 well between 3437 and 3385 m (Brun et al., 1984) were deposited
during this transgressive step (Bache et al., 2009; Bache et al., 2012). The sandstone unit
contains a clayey level at 3426.70 m depth which provided a calcareous nannoflora with
Amaurolithus primus and A. tricorniculatus (Fig. 7; Brun et al., 1984), that can be precisely
dated between 5.54 and 5.35 Ma (Di Stefano and Sturiale, 2010; Raffi et al., 2006), i.e. in
agreement with chronology of the reflooding proposed by Bache et al. (2012) (Fig. 8).
The TGS-NOPEC seismic line (Fig. 6) acquired in the Gulf of Lions in 2001 allows us to
refine our interpretation of the transition from the TRS to the evaporite units. The TRS is
characterised by its smooth aspect, the erosional truncation of the underlying series and by the
onlap termination of the overlying series (Fig. 7). Thickness map of the seismic unit
immediately above the TRS (Fig. 9) confirms its onlap configuration seaward of the
paleoshoreline preserved just before the catastrophic reflooding. Toward the basin the base of
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