Seismic Geomorphology and Stratigraphy of the Provence Shelf Since the Messinian Salinity Crisis (SE France)
Aurelie Tassy¹, Francois Fournier¹, Jean Borgomano¹, Bruno Arfib¹, Philippe Munch²,
Isabelle Thinon3, Marina Rabineau4, and Marie-Claire Fabri5
¹CEREGE, Aix-Marseille University, Marseille, France
²Geosciences Montpellier, Montpellier, France
³BRGM, Orléans, France
4Brest University. Brest. France
5Ifremer Méditerranée Laboratoire Environnement, La Seyne/Mer, France
Outcrops in Provence have been exhaustively studied, however few studies focused on the marine geology and the possible offshore continuity of onshore structures. It is a complex geological domain situated between the Alpine arc and the continental margin of the Liguro-Provençal back-arc basin which was also influenced by the high amplitude Neogene eustatic changes, especially during the Messinian Salinity Crisis (MSC).
The salinity crisis in the Mediterranean basin during the Messinian is considered as one of the most spectacular events on the marine environment since the beginning of the Neogene. During the Messinian, the reduced inflow of Atlantic Ocean water through the Betic and Rifian corridors combined to a high evaporation rate provoked a dramatic Mediterranean base level drop of at least 1500m (Benson et al., 1991; Krijgsman et al., 1999; Jolivet et al., 2008).
In South of France, most of the studies related to the MES and Plio-Quaternary deposits focused on the southwestern and central part of the Gulf of Lion margin (synthesis in Séranne, 1999 and Guennoc et al., 2000), and the Ligurian margin (Sage et al. 2011). The published maps of the MES on the Gulf of Lion margin (Gennesseaux and Lefebvre, 1980; Guennoc et al., 2000) evidence a buried Messinian drainage network comprising two main valley systems, the Rhône valley system to the northeast, and the Languedoc-Roussillon valley system to the southwest. Offshore Marseilles, bathymetric maps evidence deep canyons incising a narrow shelf break, the Cassidaigne and Planier Canyons which do not extend to the present-day coastline. In addition, the impact of the Messinian eustatic event on the coastal hydrologic systems was never investigated in this area.
This shelf cartography allows a better understanding of the geometry of Bandol and Cassidaigne Canyons. Strong lithologic and structural controls permit incision to be realized on a place affected by strong tectonics between geological units characterized by different rock hardness. Such results imply new considerations for the tectonic, stratigraphic and hydrographic framework of the Provence area.
AAPG Search and Discovery Article #120034©2012 AAPG Hedberg Conference Fundamental Controls on Flow in Carbonates, Saint-Cyr Sur Mer, Provence, France, July 8-13, 2012