Jimmy Moneron – Geological Survey of Israel

The Eastern Mediterranean Sea has always been a brain teaser to understand for structural geologists. Since the Permian, this region was in the heart of contacts between several tectonic plates involving rifting (leading to expansion) and subduction phases (to contraction) (Figure 1).

Figure 1: Simplified kinematic and tectonic sketch of the Eastern Mediterranean (modified from Le Pichon et al., 1995; Chaumillon and Mascle, 1997; McClusky et al., 2000).

Six million years ago, a dramatic event occurred and affected the whole Mediterranean Sea, an alleged partial closure of the Sea with the Atlantic Ocean involved the disruption of the main inflow of saline Atlantic water to the Mediterranean through the former Gibraltar Straits and triggered a major accumulations of evaporites [dubbed as “salt”, but generally made of gypsum (CaSO4.H2O) and anhydrite (CaSO4)].

This event is called the Messinian Salinity Crisis, it happened during the Late Miocene’s epoch and it lasted from 5.97 till 5.33 million years ago. It is still sparsely understood and needs to be intensively studied in order to be deciphered. Fifteen Ph.D Students and lots of researchers and scientists of all types are working on this problem, together within a European funded fellowship in which I am part of, called SaltGiant.

The Eastern Mediterranean region has a rich structural evolution and history, and diverse tectonic configurations, marked by sedimentary features (crustal shortening, subsidence and uplift / tilting of the margins. Active tectonics during and post-Messinian have shaped the seafloor in some basins as well as the size of the Mediterranean, and the shape and physiography of the evaporites.

In the course of my previous work with Total (a French major oil company) and helped with several leading scientists and professionals, I was studying how much volume of salt has been accumulated in the Mediterranean Sea in order to answer for instance geodynamical questions on the closure of the Gibraltar Strait during this period.

Our first findings have implications for the Mediterranean’s Messinian sequestration and desiccation scenarios since we finally figured that it was impossible for the Gibraltar Strait to be fully closed during the whole salinity crisis.

This first work triggered my ambition to study the Mediterranean Sea structure to get meaningful geodynamic models, in order to provide new clues for some controversies that still surround this event in the geological history.

Since the processes behind deformation of salt in the Eastern Mediterranean are still poorly understood there was a necessity to further investigate and emphasize the mechanism drivers involved in the structural framework in the region.

Then, my role within this fellowship is to determine and understand the structure, shape, etc. of the accumulated salt first in the Levant Basin (offshore Egypt, Israel and Lebanon) and then in a wider area, from six millions years on. One of the main rationale of my study is to see how the reconstruction of the deformation history of the Levant Basin in time and space and the mapping of deformation in several structural levels (i.e., intra-salt, top salt, top Pliocene, top Gelasian, and seafloor) would help to decipher the general salt giant dynamics and tectonic activity during the last six million years. The available extensive data gives a good coverage of the area and facilitates the comprehension of the distribution and configuration of salt, thus reducing the uncertainty associated with previous assessment.

The first step of my study consists in documentation and bibliographic review on existing related research for the Levantine Basin, its geodynamic and stratigraphic evolution. It helps to better understand the distribution and displacement of salt in my study area over time (example, Figure 2).

Figure 2: Location of section and nomenclatures of the intra-evaporite units and reflectors (Feng et al., 2016)

Since there are few studies on the evaporite sequence in itself, it is quite hard to understand its behaviour over time. In this region more particularly since it is interbedded by clastic sediments. (Figure 2). It is then also very important to understand where those clastics come from, what are the structural mechanisms involved, and what was the climate and environnement. from a local to a regional scale.

Since confusion still exists about several fundamental issues concerning the MSC event, the understanding of deformation of the salt and its overburden into the different basins will be essential for a meaningful assessment of the mechanisms involved in the context of the MSC and its aftermath.  Later on I hope I will be able to show that evaporites and their overburden are not deposited uniformly and that their deformation style is dependent to specific tectonic phase timings.

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