Refining our knowledge of the Messinian salinity crisis records in the offshore domain through multi-site seismic analysis

Abstract

The Messinian salinity crisis (MSC) [Hsü et al., 1973] has deeply shaped the Mediterranean landscape and triggered large sedimentary deposits (evaporites and clastics) in the deep basins within a short time span. Until recently, the MSC has mainly been analyzed independently, either through outcrops located onshore (e.g. Morocco, Cyprus, Spain, Sardinia, Italy) or through marine seismic profiles in the deep offshore. Each approach bears its own limitations:(1) on the one hand, land outcrops refer to incomplete Messinian successions that are geometrically disconnected from the offshore Messinian deposits owing to tectonics (e.g. Apennines) and/or because they accumulated at an early stage of the crisis in shallow marginal basins (e.g. Spain); (2) on the other hand, seismic profiles from the upper margins down to the deep basins allow to image and explore the entire MSC event as a continuous process, but with a lower resolution and with a lack of stratigraphical and lithological control, in the absence of full recovery of scientific boreholes.We present here a synthesis of a set of modern geophysical data over the Mediterranean and Black seas allowing to image the Messinian markers (erosion surfaces, depositional units and their bounding surfaces) much better than previously and to study the spatio-temporal organisation of these markers from the inner-shelves down to the bathyal plains. The results from thirteen areas located offshore are compared, with common charts and nomenclatures. The comparative and multi-site approach developed here allows to analyse the record of the MSC on margin segments and basins that depict various structural, geodynamical and geological settings, to fix a number of local influencing factors (tectonics, subsidence, inherited topography, sedimentary fluxes...) and to partly assess their influence in facies and geometrical variations of the MSC units. We are thus able to extract from our analysis some recurrent signals related to the MSC ss., allowing us to discuss: (1) the amplitude and modalities of base-level changes during the MSC; (2) the depositional modalities of the MSC units in the deep basins; (3) the location of the erosion product of the margins and to emphasise (4) the major differences between the eastern and western Mediterranean basins. Une meilleure connaissance des enregistrements de la crise de salinité messinienne en domaine marin grâce à l'analyse sismique multi-sitesMots-clés. -Crise de salinité messinienne, Méditerranée, Profils sismiques, Evaporites, Erosion, Clastiques.Résumé. -La crise de salinité messinienne (CSM) [Hsü et al., 1973] a profondément modelé les paysages méditerra-néens et généré d'épaisses accumulations sédimentaires (évaporites et dépôts clastiques) dans les bassins profonds sur une brève période de temps à l'échelle géologique. Jusqu'à présent, la CSM a principalement été étudiée distinctement, à terre, grâce aux affleurements (ex. Maroc, Chypre, Espagne, Sardaigne, Italie…), et en domaine marin, par l'intermé-diaire de profils sismiques. Chacun...

Seismic imaging of Late Miocene (Messinian) evaporites from Western Mediterranean back-arc basins

“…The reason for the 's' layer not being identified in other parts of the Western Mediterranean is probably two-fold: (1) the relatively high resolution of the deep-water seismic survey of the datasets analysed in this study; and (2) the possible dilution of gypsum and salt by clastics in the peripheral areas of the Western Mediterranean, with particular reference to the Gulf of Lion depocentre where most of the available information comes from. Following the MSC evolutionary model of Rouchy & Caruso (2006), Ryan (2008) and Lofi et al (2011b), we infer that the deposition of the 's' layer followed a second, short decrease in the base level. This secondary base level drop is correlatable to the intra-UU erosion (IES), which is well defined on the Sardinian continental slope (see also Geletti et al 2014).…”

Modelling global-scale climate impacts of the late Miocene Messinian Salinity Crisis

“…Flecker and Ellam, 2006;Fortuin and Krijgsman, 2003;Krijgsman and Meijer, 2008;Lugli et al, 2010;Meijer, 2012;Topper et al, 2011). In addition, it is difficult to envisage how enough salt could have been brought into the Mediterranean to explain the 1-3 km-thick Messinian evaporite sequence visible in the seismic record (Lofi et al, 2011;Ryan et al, 1973) without inflow from the Atlantic.…”

Evidence for deep-water deposition of abyssal Mediterranean evaporites during the Messinian salinity crisis

“…Seismic profiling has also revealed an erosional unconformity around the higher parts of the Mediterranean, and reworking of evaporite detritus into the lower parts of the basin (e.g. Lofi et al, 2011). Hydrologic (Debenedetti, 1982;Blanc, 2006;Meijer and Krijgsman, 2005) and isostatic (Norman and Chase, 1986;Govers et al, 2009) modeling have helped clarify the response of the basin to changing climate, water supply, and sediment and water loads.…”