Evidence of sea level drawdown at the end of the Messinian salinity crisis and seismic investigation of the Nahr Menashe unit in the northern Levant Basin, offshore Lebanon

Abstract

Several important aspects of the Messinian salinity crisis (MSC) are still subject to controversy and debate after more than 40 years of studies. Recent work from the eastern Mediterranean have provided a renewed stratigraphic framework for the basin that is inconsistent with previous interpretation studies in the area. This study presents a description of the evolution of the depositional environment in the northern Levant Basin in a time interval surrounding the end of the famous event, from Late Messinian to the Pliocene. Through seismic mapping, we have identified a sediment package overlying the intra‐Messinian truncation surface (IMTS). This package is interpreted as an axial fluvial system running along the Levant Margin in stage 3 of the salinity crisis, likely composed of redeposited evaporites and clastic material. The system was fed primarily from a large fan system building out from the basin margin during a time of sea‐level low stand following a major erosional event, and presumably also from similar systems along the Latakia Ridge and Syria. Our interpretation also lends weight to the theory of a subaerial origin for the truncation surface after a catastrophic desiccation event succeeding the deposition of the halite‐dominated Messinian evaporite succession, based on differences in maximum erosional depth throughout the basin. After the deposition of the post‐IMTS package, deep marine settings were restored in the basin, and hemipelagic sediments from the Nile Delta and the Levant Margin have dominated the sediment deposition since.

Integrated isotopic and organic geochemical constraints on the depositional controls and source rock quality of the Neogene Kalamaki sedimentary successions (Zakynthos Island, Ionian Sea)

“…During this period, a significant aridification (Vasiliev et al 2017) and cooling (Tzanova et al 2015;Herbert et al 2016;Holbourn et al 2018;Kontakiotis et al 2019) trend was evidenced, whereas enhanced ocean stratification, bottom water anoxia, and salinity increase were reported within the drawdown water column of the Mediterranean basin (Flecker et al 2015;Moissette et al 2018;Vasiliev et al 2019;Isaji et al 2019a;Kontakiotis et al 2019). This multifactorial scenario is compatible with the widespread deposition of preevaporitic sediments, which grade upward into the evaporitic succession during the sea-level drop (Kartveit et al 2019;Madof et al 2019), with favorable conditions for the preservation of the organic matter (Demaison 1991;Schenau et al 1999;Vasiliev et al 2019) (Fig. 8).…”

The demise of a ‘salt giant’ driven by uplift and thermal dissolution

“…The deposits immediately above the Mobile Unit in the South Levant Basin have been calibrated by wells and divided into two units/formations by Druckman et al (1995) and Gvirtzman et al (2017): Unit and Afiq Formation, with the evaporites restricted to Unit (Gvirtzman et al, 2017). The upper Messinian fluvial accumulation of the Nahr Menashe also directly overlies large sections of the Mobile Unit in the central-north Levant and Cyprus Basins offshore Lebanon and Syria (Kartveit et al, 2019;Madof et al, 2019).…”

“…Two competing models for the origin of the IMTS are (1) subaerial erosion linked with relative sea-level fall (Bertoni and Cartwright, 2007;Kartveit et al, 2019) that is locally in parts of the basin combined with/superimposed to tectonics (Maillard et al, 2011), or (2) subaqueous dissolution in a stratified water column in a deepwater setting where the tilted basinal evaporites were uplifted above a chemocline along the basin margin (Gvirtzman et al, 2017).…”

“…The extent of intra-Messinian truncation in the Eastern Mediterranean has until now been described primarily in the marginal domains of the Levant Basin (Bertoni and Cartwright, 2007;Lofi et al, 2011b;Feng et al, 2017;Gvirtzman et al, 2017), in the Cyprus Basin and Latakia Basin (Lofi et al, 2011b;Maillard et al, 2011) and recently within a small section of the wider axial domain of the salt basin (Kartveit et al, 2019). Relative sea-level fall (Bertoni and Cartwright, 2007;Kartveit et al, 2019), possibly locally combined with/superimposed to tectonics (Maillard et al, 2011), have been proposed to have led to subaerial exposure and erosion. An alternative model for the IMTS in the marginal Levant Basin was recently proposed by Gvirtzman et al (2017).…”

The Zanclean megaflood of the Mediterranean. Searching for independent evidence

“…To add to these conflicting observations, recent industrial seismicreflection data-sets in the deep Ionian Sea (Sirt Basin, Libya) and in the deep Levant Basin (offshore Syria) show the existence of large fluvial sedimentary systems formed after the halite precipitation (Bowman, 2012;Madof et al, 2019). In the Levant, these fluvial systems are longer than 100 km and interpreted as fluvio-deltaic lobes resting directly atop the Messinian halite and seem coeval with the erosion of deformed salt layers (Bowman, 2012;Kartveit et al, 2019;Madof et al, 2019). These are interpreted as the result of vast paleo-river basins draining areas of Africa and the Middle East region during the lowering of the Mediterranean Sea level.…”