The Messinian salinity crisis: open problems and possible implications for Mediterranean petroleum systems

Abstract

A general agreement on what actually happened during the Messinian salinity crisis (MSC) has been reached in the minds of most geologists but, in the deepest settings of the Mediterranean Basin, the picture is still far from being finalized and several different scenarios for the crisis have been proposed, with different significant implications for hydrocarbon exploration. The currently accepted MSC paradigm of the 'shallow-water deep-basin' model, which implies high-amplitude sea-level oscillations (> 1500 m) of the Mediterranean up to its desiccation, is usually considered as fact. As a consequence, it is on this model that the implications of the MSC events on the Mediterranean petroleum systems are commonly based.In fact, an alternative, deep-water, non-desiccated scenario of the MSC is possible: it (i) implies the permanence of a large water body in the Mediterranean throughout the entire Messinian salinity crisis, but with strongly reduced Atlantic connections; and (ii) envisages a genetic link between Messinian erosion of the Mediterranean margins and deep brine development.In this work, we focus on the strong implications of an assessment of the petroleum systems of the Mediterranean and adjoining areas (e.g. the Black Sea Basin) that can be based on such a non-desiccated MSC scenario. In particular, the near-full basin model delivers a more realistic definition of Messinian source-rock generation and distribution, as well as of the magnitude of water-unloading processes and their effects on hydrocarbon accumulation.

Restored topography of the Po Plain‐Northern Adriatic region during the Messinian base‐level drop—Implications for the physiography and compartmentalization of the palaeo‐Mediterranean basin

“…(), Roveri et al. () for the entire Mediterranean area. This result implies that, at a broader scale, during maximum sea‐level fall, the Mediterranean was divided into at least three sub‐basins (the two major western and eastern Mediterranean Basins and PPNA) with independent base‐level evolutions and water budgets. The separation from the rest of the Mediterranean can partly explain the lack of halite and potassium‐rich salts in the Po Plain area and Adriatic Sea. The present‐day fluvial network flows directly above buried incised valleys into the Southern Alpine basement below the Po Plain.…”

“…Roveri et al. () extended the proposal of a relatively minor MSC sea‐level drop (100–200 m) to the entire Mediterranean, in contrast with other estimates suggesting between 1,300 and 2,000 m of sea‐level drop (Ryan, ; Stampfli & Hocker, ; Clauzon, Suc, Gautier, Berger, & Loutre, ; Krijgsman et al., ; Blanc, ; Meijer & Krijgsman, ; Maillard & Mauffret, ; Urgeles et al., ; Cameselle & Urgeles, ; see Vai, for a review; Sternai et al., ).…”

“…(), Roveri et al. () based on modelling submarine dense water cascading from the shelf areas producing canyons without the need of significant drawdown. Roveri et al.…”

“…(), Roveri et al. (). We take advantage from high‐resolution stratigraphic data (e.g., sedimentological, palaeontological, and geochemical data) and detailed geological constraints (e.g., seismic‐based and well logs) for the study region also provided by recent works (Ghielmi, Minervini, Nini, Rogledi, & Rossi, , ; Rossi, ; Rossi, Minervini, & Ghielmi, ; Rossi, Minervini, Ghielmi, & Rogledi, ).…”

“…We model the sea-level drop of the Po Plain-Northern Adriatic foreland basin (PPNA) during the Messinian based on its detailed stratigraphic record in order to better understand its connectivity with the rest of the Mediterranean Sea during the MSC. To this aim, we analyse public and private (courtesy of Eni Upstream) subsurface data and carry out a 3D reconstruction of the subaerial and submarine landscape of the Po Pain and Adriatic foreland during the MSC desiccation peak, that is, after the MSC stage 1 according to the chronostratigraphy by Roveri, Flecker, et al (2014), , Roveri et al (2016). We take advantage from high-resolution stratigraphic data (e.g., sedimentological, palaeontological, and geochemical data) and detailed geological constraints (e.g., seismic-based and well logs) for the study region also provided by recent works (Ghielmi, Minervini, Nini, Rogledi, & Rossi, 2010, 2013Rossi, 2017;Rossi, Minervini, & Ghielmi, 2018;Rossi, Minervini, Ghielmi, & Rogledi, 2015).…”