An Offshore View of the Messinian Salinity Crisis: A review
Christian Gorini, Lucien Montadert, Marina Rabineau, and Francois Bache
The Late Miocene isolation of the Mediterranean also known as the Messinian Salinity Crisis, is characterized by widespread deposition of basinal and marginal evaporites and erosion of the surrounding margins. An almost complete record of this episode, the events leading to it as well as its consequences, is preserved in the deep eastern and deep western Mediterranean. The recent interest in below-salt hydrocarbon resources around the world makes the pre-halite record of the Mediterranean particularly attractive to the Exploration community. Early seismic profiles had first revealed the presence of evaporites below the seafloor and they were soon verified in 1970 by DSDP drilling. However, since then, three more drilling expeditions have only managed to sample the top ~26 m of the evaporites in the Mediterranean due to technological limitations. New seismic data from the Western and Eastern Mediterranean indicate that the response of the sedimentary architecture to external forcing is complex and variable in term of seismic facies. New observations indicate high rates of erosion and redeposition of thick low stand silicoclastic deposits during the event in front the big deltas (Nile ,Rhone) and even in areas of more moderate clastic input (Levantine and Turkish margins) . Seismic profiles show that this huge Messinian lowstand is deposited in an already hypersaline environment, probably in a very short time. Two depositional megasequences have been identified for the deep salt, with a lower unit associated with the formation of Messinian lowstands deltas, and an upper salt/evaporites, associated with a low imput of silicoclastic in the deep basins. Inside these two megasequences, more sequences can be defined following the resolution of the seismic data. The top of the messinian upper unit is clearly infilling incised valleys and onlaping erosional surfaces of the Messinian slopes. The final stage of the Messinian salinity crisis and reflooding is recorded all around Mediterranean by deep incisions, abrasions and/or reworked material covered by Pliocene hemipelagic muds.
In conclusion the key seismic surfaces and facies observed all around Mediterranean provide distinctive reference and correlation surfaces, even if they can’t be precisely dated today.
AAPG Search and Discovery Article #90161©2013 AAPG European Regional Conference, Barcelona, Spain, 8-10 April 2013