1 de setembre de 2021
Heida, H., Raad, F., Garcia-Castellanos, D., Jiménez-Munt, I., Maillard, A. and Lofi, J. (2021), Flexural-isostatic reconstruction of the Western Mediterranean during the Messinian Salinity Crisis: implications for water level and basin connectivity. Basin Research. https://doi.org/10.1111/bre.12610
Abstract
During the Messinian Salinity Crisis (MSC, 5.97-5.33 Ma), thick evaporites were deposited in the Mediterranean Sea associated with major margin erosion. This has been interpreted by most authors as resulting from water level drop by evaporation but its timing, amplitude and variations between subbasins are poorly constrained due to uncertainty in post-Messinian vertical motions and lack of a clear time-correlation between the marginal basin and offshore records. The Balearic Promontory and surrounding basins exemplify a range of responses to this event, from margin erosion to up to a kilometer thick Messinian units in the abyssal areas containing the majority of the MSC halite. The Balearic Promontory contains unique patches of halite with thickness up to 325 m at intermediate depths that provide valuable information on water level during the stage of halite deposition. We compile seismic markers potentially indicating ancient shorelines during the drawdown phase: the first is marked by the transition from the MES to UU based on seismic data. The second is the limit between the Bottom Erosion Surface and abyssal halite deposits. We restore these shorelines to their original depth accounting for flexural isostasy and sediment compaction. The best fitting scenario involves a water level drop of ca. 1100± 100 m for the Upper Unit level and 1500±100 m for the Bottom Erosion Surface level. According to our results, halite deposition began in the Central Mallorca Depression at 1300-1500 m depth, perched hundreds of meters above the deep basins, which were at 1500-1800 m (Valencia Basin) and >2900 m (Algerian Basin). The hypothesis that erosion surfaces were formed subaerially during the drawdown phase is consistent with a model of halite deposition before/during the water level drop of at least 1000 m, followed by the deposition of the Upper Unit until the MSC is terminated by reinstatement of normal marine conditions.