Ronja Ebner (ESR 7)– Utrecht University (Netherlands).


“There is a theory which states that if ever anyone discovers exactly what the Universe is for and why it is here, it will instantly disappear and be replaced by something even more bizarre and inexplicable.

There is another theory which states that this has already happened.” [1]

When one starts to find their way into Geology and Geosciences in general, it is important to understand how this wonderful branch on the tree of science works. I might be biased, but I am perfectly sure that the Mediterranean Salinity Crisis is the perfect study object to understand those mechanisms and dynamics. Learning about that topic one will not only find discussions about data interpretation, the role of “chicken wire”, the probabilities of desiccation or a Mega Flood as well as the rise and the fall of theories, but also the collaboration of scientists with completely different backgrounds.

This of course implies that work on the MSC seldom is a stand-alone. Luckily one of us is focussing on unravelling this complex branched process of figuring-out. And I am pretty sure that the work of Bea (ESR 15) is going to be a thriller!

For everybody who does not want to wait, the paper by Angelo Camerlenghi and Vanni Aloisi is good first step towards a better understanding of this controversy (it will be comming soon here!).

This paper offers a overview over the controversies that still dwell around this “youngest salt giant on Earth” and gives some insights into the way scientific theories evolve and why often it is important and rewarding to think broader than just strait forward.

Layer thickness 1.5 km Time of deposition ~5.5 million years ago
volume ~1 000 000 km³ Amount of Salts >6% of dissolved salt of global oceans

Table 1: Why the Mediterranean Salt Giant is amazing: A data sheet.

Illustration 1: A panoramic view of the geological formation “Vena del Gesso”  in thenorthern Apennines (Italy).
Illustration 2: Chicken-wire structure from a DSDP drill core.

Although this MSG is hidden “beneath the deep ocean floor”[2], the “crisis of salinity” [3] caused curiosity among scientists before they actually knew about the existence of the MSG.

In 1960 Raimondo Selli made a link between the sedimentary sequences he saw in the Appennines and the evaporational sequence we know from experiments. “His reasoning was straightforward and based on solid geological ground”, but did not include the trigger for this situation. So, things got more complex when in 1973 more evaporictic rocks where found. This source of new information was not only hidden beneath the sea floor but also was  “equivalent in age and mineralogy to those described by Selli in the Apennines of Italy”.

This discovery in combination with chicken-wire (see illustration 2) nodular anhydrite and algal stromatolites, that needed light to exist at the time of seawater evaporation”, and “the existence of very deep erosional valleys, some of which buried by sediments” lead to the theory of a desiccated Mediterranean basin. This theory, maybe because of its extremity and inspirational character for fantastic scenarios, “ was successful not only among the scientific community, but also in the public opinion”. This theory though was not the only one, since the amount of evaporites could also be explained with non-desiccation models. And soon the controversy on the “what exactly happened”-question  emerged and is still living. Since then a broad variety of scientists  is working on that matter with the result that around  “1800 research articles have been published about the MSC, [although still] no consensus exists on the tectonic, climatic and hydro-geo-chemical processes that led to the deposition of the Messinian evaporite”[2].

Illustration 3: Picture of the Dead Sea used to visualise a desiccated Mediterranean.

One way to structure those efforts is COST (European Cooperation in Science and Technology). This cooperation coordinates the project MEDSALT and later on promoted the SALTGIANT project, a Marie Skłodowska-Curie European Training Network, of which I am a part of. “In all 200 scientists are working together across disciplines such as geophysics, geology, biology, microbiology, embracing also social sciences”[2]. This will lead to a broader evaluation of the data and maybe to new insights, although “[at] present, scientists agree to state that the controversy has no solution unless new data, in particular from the deep basins, is acquired and integrated to evaluate existing – or novel – MSC scenarios”[2].  And so, we are hoping that Japanese research vessel Chikyu will drill into the salts to gather even more information.

The main thing I learned  from the MSC ( and on what the paper focusses on) is, that collaboration between disciplines and more data is important.


“There is a theory which states that if ever anyone discovers evidence to falsify one endorse another idea, it [ the idea]  will instantly disappear and be replaced by something even more bizarre and inexplicable.

There is another theory which states that this has already happened.”

[loosely based on 1]


References:

[1] Douglas Adams, Intro to “The restaurant at the end of the universe”.

[2] Angelo Camerlenghi and Vanni Aloisi (2019) “Uncovering the Mediterranean salt giant (MEDSALT) – Scientific Networking as incubator of cross-disciplinary research in Earth Sciences”, to be published in European Review.

[3] Adams et al., “The Messinian salinity crisis and evidence of late Miocene eustatic changes in the world ocean”, 1977, Nature

[4] 23. Sedimentary petrology and strucures of Messinian evaporictic sediments in the Mediterranean Sea, LEG 42A, Deep Sea Drilling Project. Accessed through: http://www.deepseadrilling.org/42_1/volume/dsdp42pt1_23.pdf

[5] Marc Arenas Camps, 05/11/2015, How many species live in the Mediterranean Sea and other curiosities. https://allyouneedisbiology.wordpress.com/2015/11/05/species-mediterranean-sea/

[Title picture] FAZ, 10.5.2004, Ivan Steige.

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