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

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tel-00790852, version 1 - 21 Feb 2013 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 generate subsidence in the central basins. However the observation of transgressive ravinement surfaces in the Valencia Trough (García et al., 2011) and possibly in the Alboran margin (Estrada et al., 2011) as well as the necessity of water inputs from oceans to precipitate evaporites suggest a combination of subsidence and increase of the Mediterranean sea-level (Bache et al., 2012). This context coupled with a high evaporation rate was favorable to precipitate thick evaporites at the centre of the Mediterranean after the major Messinian drawdown dated at 5.60 Ma (Butler et al., 1995; Butler et al., 1999; CIESM, 2008; Clauzon et al., 1996; Riding et al., 1998) and before the catastrophic reflooding of the Mediterranean at 5.46 Ma (Bache et al., 2012), followed by a continuing sea-level rise well- documented at 5.332 Ma (Hilgen and Langereis, 1993; Lourens et al., 2004; Van Couvering et al., 2000). Here, we assume sufficient water inputs from ocean after the Messinian drawdown and before the catastrophic reflooding. Recent numerical models suggest that such water input is insufficient or unlikely to occur after the closure of the Rifian Corridor (Blanc, 2002; Garcia- Castellanos et al., 2009; Govers, 2009; Govers et al., 2009). The numerous uncertainties on models constraints (erodibility, uplift rate, climate data…) and the lack of alternative conceptual scenarios consistent with our observations do not allow to discard our assumptions. Loget et al. (2005) have shown that intense regressive erosion developed inevitably in the Gibraltar area after the Messinian drawdown. It should be a likely process to explain a continuous input of marine waters necessary to precipitate enough evaporites in the desiccated Mediterranean Basin. In the Eastern Mediterranean, wave ravinement surfaces comparable to the TRS observed in the Gulf of Lions have been observed off the Nile Delta in the interfluves bordering the Abu Madi canyon, where it contrasts sharply with the lowermost part of the canyon fill (Dalla et al., 1997). A series of flat ravinement surfaces have also been identified in the Levantine 14
tel-00790852, version 1 - 21 Feb 2013 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 Basin and ascribed to wave erosion (Bertoni and Cartwright, 2006). Our interpretation of the TRS in the Gulf of Lions (and Western Mediterranean) provides good perspectives to discuss the occurrence of step II in Eastern Mediterranean and to compare the evolution of these two parts of the Mediterranean during the peak of the MSC. 5.3. Step III, instantaneous catastrophic reflooding: prograding Gilbert- type fan deltas and completed inundation In several places in the Mediterranean Basin, it has been observed that the post-Crisis marine reflooding preceded the Zanclean GSSP (Calabria: (Cavazza and DeCelles, 1998); Dardanelles Strait: (Melinte-Dobrinescu et al., 2009); Sicily: (Londeix et al., 2007); Apennine Foredeep: (Popescu et al., 2007)). Indeed, this extremely fast reflooding has been dated at 5.46 Ma (Bache et al., 2012), i.e. about 128 kyrs before the Zanclean GSSP corresponding to the base of the Trubi Formation in Sicily dated at 5.332 Ma (Lourens et al., 2004; Van Couvering et al., 2000). The excessively brief duration of this episode [comprised between
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Quantification des flux sédimentaires et de la subsidence du bassin ...

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