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"According to the logbook entry, we only left Lisbon on August 14th [1970], and we set off precisely at zero o'clock one minute," noted Kenneth J. Hsü, scientific leader of the Glomar Challenger marine expedition (LEG 13) together with Bill Ryan, in the summer of 1970 - which can be read in his book "The Mediterranean was a desert. On research trips with the Glomar Challenger". The fact that the drilling ship with a displacement of 11,000 tons and the 60 meter high drilling tower left the harbor exactly one minute after midnight is probably due to the superstition of the sailors, who would not have liked to leave on the 13th. The ten-person scientific crew consisted of Jennifer M. Lort (Cambridge) and Maria B. Cita (Milan), two female and eight scientists, including the paleontologist Herbert Stradner, born in 1925, from the Federal Geological Institute in Vienna. The aim was to explore the subsurface of the Mediterranean Sea with drilling and to derive information about age and formation from the analysis of the rock samples obtained.
Unplanned stop in the Atlantic
According to the plan, the Glomar Challenger was supposed to sail from Lisbon via the Strait of Gibraltar directly into the Mediterranean. But things turned out differently. The book "Science Adventures - Explorers between the Alps, the Orient and the Arctic Ocean" says the following: "On the day of departure, Bill Ryan came forward with a request from his French friend, the geologist Xavier Le Pichon: He had asked him to drill a hole in the Atlantic on the Gorringe Bank. Le Pichon wanted to get geological evidence for his plate tectonic concepts. Hsü and other crew members were by no means impressed by this. In the end, they drilled; the result Drilling core made of ophiolite (green ocean bed rock) from a depth of 1,711 meters confirmed that rocks from the Tethys (Ocean of the Mesozoic Age) are also present here, comparable to those known from the Alps. With this initial result, even the initial skeptics were convinced and - now with an initial feeling of success - left this unplanned drilling site with joy.
Southeast of the Balearic Islands: Borehole 124 with evaporite
After just two weeks, on August 28, 1970, the scientists had solid evidence from a depth of around 3,000 meters. The drill, which usually penetrates the soft ocean floor sediments several meters per minute, had penetrated a hard layer of rock in borehole 124 south of Mallorca. This layer was known from geophysical studies and was called the "M layer", but they did not know what it consisted of. When Hsü and Ryan saw the core of the "M layer" at the laboratory table on the Glomar Challenger, they were amazed. The drill core, several meters long, consisted of thin layers of algae (stromatolite) and anhydrite, chemically calcium sulfate. In contrast to gypsum, also a calcium sulfate, anhydrite has no water molecules in the crystal lattice. Such sediments (evaporites) form in extremely dry climates with high evaporation rates.
Everyday scientific work on board
Herbert Stradner, a world-renowned specialist for calcareous nannofossils (smaller than 30 micrometers) - he described around 100 new species for the first time and some were named after him - still remembers what it was like on the Glomar Challenger in 1970. "When the drilling was in full swing, a new core arrived every hour. It was called 'Core up!', and then all of a sudden all the investigations began. During the drilling process, the core itself was pushed into a 9 meter long plastic tube, which was then pulled up using a cable pull. The 9 meter long piece was first placed on the deck and cut into pieces so that the core sections could be carried comfortably. The cores were then cut open lengthways in the laboratory. One half went into the archive, the other half was The untouched half was carefully photographed, in black and white and in color. Only then were we allowed to take out sediment samples for micropaleontological, nannopaleontological and sedimentological examinations [...] My task was to determine the nannofossils (small fossils) in the sediment in order to date the rock age of the seabed layers as accurately as possible 1000x magnification. The biggest problem on board was the stable position of the microscope. In order to get a steady image, the microscope was placed on an air ring cushion and was also lashed to the work table with rubber straps so that it would not fall off the table in heavy seas. This was the only way to do microscopy on board, but only up to around wind force 5. From wind force 5 it is impossible to see the human head with the optical axis of the microscope."
Stradner was able to quickly classify the age of the sediments on board using nannofossils. Maria B. Cita was able to draw conclusions about the deposition conditions of the sediments using microfossils, especially foraminifera (single-celled protists).
The article in “Nature” raises questions
When they returned to Lisbon on October 6, 1970, they had made groundbreaking discoveries but also brought with them many questions. On September 18, 1972, Hsü, Ryan and Cita sent their results to the editors of the renowned journal "Nature" under the title "Late Miocene Desiccation of the Mediterranean". On March 23, 1973, their work on the desiccation of the Mediterranean in the late Miocene was finally published. In terms of time, this is the geological period of the Messinian (7.25 to 5.33 million years before today), the uppermost stage of the Miocene, which began 23.03 million years ago. The drying out of the Mediterranean around six million years ago, which was unknown until August 1970, entered the specialist literature as the Messinian salinity crisis (MSC).
The researchers were surprised not only by the fact that evaporites, rocks from extremely shallow deposits, were found, but also by the fact that there were pronounced deep-water deposits above and below and even between the evaporites. They saw here proof that the Mediterranean was already a deep sea basin at that time. The flooding with Atlantic sea water took place via the Strait of Gibraltar. Hsü, Ryan and Cita looked for answers ("Explaining an Improbable Fact") and concluded their article in "Nature" with an appeal to their colleagues: "We welcome comments from our colleagues in the Earth and biological sciences, ..."
PS: Five years later, in 1975, Expedition 42A, again with Hsü and Cita on board, provided further evidence of the dry Mediterranean in the eastern area. Since then there have been no further scientific drillings in the Mediterranean. The IOPD program plans to drill again in the next few years. (Thomas Hofmann, August 14, 2020)