Conference:
32nd International Geological Congress, Florence, Italy, 20-28 August 2014, Session G21.11 – Sedimentary records of catastrophic events
Authors:
Georges Clauzon, Jean-Pierre Suc, Speranta-Maria Popescu.
Abstract:
Major sea-level changes occurred in the Mediterranean Sea in Late Messinian–Early Zanclean, due to Antarctic glacials (OIS TG22, TG20) and the following warming up, then to the tectonic closure of the Rifian corridor and the erosional opening of the Gibraltar Strait.These events resulted in successive sedimentations or erosions in the Mediterranean margins or deep basins:(1) evaporite deposition (thick halite in some places) on margins (sea-level fall due to Antarctic glacials, probably emphasized in the Mediterranean) (5.96-5.80 Ma);(2) deposition of a transgressive body (gypsum-clay alternations in Sicily overlain by the so-called Lago Mare and the Arenazzolo Formations, clays in other coastal basins) related to a global sea-level rise (warming up documented by OIS 19 to 15) (5.80-5.70 Ma);(3) strong erosion on the margins (interrupted in some basins such as the Po Valley which evolved separately as a perched endoreic lake) and deposition of thick evaporites in the deep desiccated basin because of the isolation of the Mediterranean Sea from the Atlantic Ocean (complete closure of the Rifian corridor) (5.70-5.33 Ma);(4) deposition of Gilbert deltas in the rias resulting from the Zanclean waters filling the canyons cut by rivers during the previous sea-level drop; they concern all the Mediterranean margins including some extra-Mediterranean areas such as the Dacic Basin; they developed in the earliest Zanclean time during which the deep basin was starving (5.33-4.0 Ma); this is the coastal signature of the Zanclean flooding of the Mediterranean Sea before the continental shelf was reconstructed. Phase 1: only the margins were desiccated whereas the Mediterranean Sea was connected with the Atlantic Ocean, but at a relative low sea-level. Phases 2 and 4: the Mediterranean Sea was at high sea-level as the global ocean and connected to the Eastern Paratethys (i.e. the Dacic Basin and later the Black Sea). Phase 3: the Mediterranean Sea was disconnected from the Atlantic Ocean and evolved as an endoreic realm while some perched basins were still full of fresh- to brackish waters (N Adriatic-Po Valley, N Dacic Basin). Lago Mare corresponds to three events (two resulted from high sea-level Mediterranean Sea-Eastern Paratethys exchanges, well documented on the margins by dinocysts at 5.7 and 5.33 Ma; one due to the replacement of ultra-salted lagoons by freshwater lakes in the deep desiccated basin at ca. 5.35 Ma, only recorded in deep wells).