The Black Sea and Caspian Sea are the present-day remnants of a much larger epicontinental
sea on the Eurasian continental interior, the Paratethys. During the late Miocene
Messinian Salinity Crisis (MSC), a unique oceanographic event where 10% of the salt
in the world's ocean got deposited in the deep desiccated basins of the Mediterranean,
the Paratethys Sea was connected to the Mediterranean Sea. Unlike the Mediterranean,
no salt is known to have been deposited in the Paratethys region at this time, yet
a similar mechanism of deep desiccation (with a water level drop of up to 2 km occurring
at 5.6 Ma) has been proposed in the past to explain the late Miocene and Pliocene
Paratethys basin evolution.
Here, we review the basin evolution, stratigraphy and subsurface data of the four
main Paratethyan sub basins to investigate the response to the Mediterranean Messinian
event. We show that hypotheses of a Paratethys-wide desiccation synchronous to the
Messinian Salinity Crisis climax at 5.6 Ma do not hold. Determinations of the magnitude
of the sea level drop appear to have regularly been overestimated by speculative basin-to-margin
interpretations, and often been disproven by increased age model resolution.
In the Euxinian (Black Sea) Basin, the most recent estimates for the magnitude of
sea level drop vary between 50 and 500 m, yet the timing is debated. Marginal outcrops
in the Dacian Basin highlight multiple switches from shallow basinal to littoral and
fluvial environments during the MSC interval, but no major water level drop coincides
with the 5.6 Ma event. The Paleo-Danube deposits filling in the Pannonian Basin do
not indicate any influence by the MSC and show prograding patterns into the deepwater
lake Pannon. The dramatic expansion of the Paleo-Volga delta in the Caspian Sea is
shown to be younger than the MSC, while estimates of the amount of water level drop
vary widely due to the poorly understood contribution of tectonic processes.
These changing perspectives and decreasing estimates of water level lowering are not
surprising given the vast northern drainage of the Paratethys region. Precipitation
and runoff from the Eurasian continent ensures a much more positive hydrological budget
under isolated conditions than the vast negative hydrological budget of the Mediterranean
Sea which requires constant compensation by infiowing oceanic waters.