The Messinian Salinity Crisis deposits in the Balearic Promontory: An undeformed analog of the MSC Sicilian basins??

Abstract

The Messinian Salinity Crisis (MSC) is a controversial geological event that influenced the Mediterranean Basin in the late Miocene leaving behind a widespread Salt Giant. Today, more than 90% of the Messinian evaporitic deposits are located offshore, buried below the Plio-Quaternary sediments and have thus been studied mainly by marine seismic reflection imaging. Onshore-offshore records’ comparisons and correlations should be considered a key approach to progress in our understanding of the MSC. This approach has however not been widely explored so far. Indeed, because of the erosion on the Messinian continental shelves and slopes during the MSC, only few places in the Mediterranean domain offers the opportunity to compare onshore and offshore records that have been preserved from erosion. In this paper, we compare for the first time the MSC records from two basins that were lying at intermediate water depths during the MSC and in which salt layers emplaced in topographic lows: the Central Mallorca Depression (CMD) in the Balearic Promontory, and the Caltanissetta Basin (CB) in Sicily. The reduced tectonic movements in the CMD since the late Miocene (Messinian) till recent days, favored the conservation of most of the MSC records in a configuration relatively close to their original configuration, thus allowing a comparison with the reference records outcropping in Sicily. We perform seismic interpretation of a wide seismic reflection dataset in the study area with the aim of refining the mapping of the Messinian units covering the Balearic Promontory (BP) and restituting their depositional history based on a detailed comparison with the Messinian evaporitic units of the Sicilian Caltanissetta Basin. We discuss how this history matches with the existing 3-stages chrono-stratigraphic model. We show that the Messinian units of Central Mallorca Depression could be an undeformed analog of those outcropping on-land in the Sicilian Caltanissetta Basin, thus questioning the contemporaneous onset of the salt deposition on the Mediterranean scale. We show a change in seismic facies at a certain range of depth between stage 1 MSC units, and wonder if this could reflect the threshold/maximum depth of deposition of bottom growth PLG selenites passing more distally to pelagic snowfall cumulate gypsum. Moreover, we confirm that PLG could be deposited in water depths exceeding 200 m.