Abstract
In the Late Cretaceous, the Eastern Mediterranean looked very different. Turkey as it is today did not yet exist and instead there was the Neotethys Ocean. The tectonic terranes that make up contemporary Turkey were scattered throughout this ocean. The Strandja, Istanbul en Sakarya terranes (Northern Turkey) were part of
... read more
the southern margin of Eurasia while the Anatolide-Taurides, Central Anatolian Crystalline Complex, Bitlis and Pütürge complexes (Southern Turkey) were scattered throughout this ocean. They were initially part of Gondwana but broke away in the Early Permian and subsequently drifted northwards, facilitated by subduction of the Neotethys beneath the southern margin of Eurasia. Subduction was followed by continental collision between the Gondwana-derived tectonic terranes and the southern margin of Eurasia in the Late Cretaceous-Eocene. This resulted in the Alpine-Himalayan orogenic belt. The uplift associated with the formation of this orogenic belt separated at the start of the Oligocene the shallow sea that covered a large part of Eurasia from the Neotethys. The latter sea is since then referred to as the Paratethys. At the start of the late Miocene, the Paratethys had shrunk significantly and only the Caspian Sea, Black Sea and the Pannonian basin remained open. Being isolated from the rest of the oceans, the sea level in the Paratethys was sensitive to fluctuations in climate. In the late 1970’s, evidence was found for the existence of a shallow marine environment in the Black Sea (Paratethys) during the late Miocene at a depth of more than 1700 meters. Using a computer model, I estimated that the sea level drop should have been between 1730 and 2230 meters to account for these observations. Central Turkey is part of the Alpine-Himalayan orogenic and characterized by a high mean elevation (1000 meters). Geological observations suggest that Central Turkey obtained its high elevation after the Cretaceous-Eocene continental collision in the Miocene. This raises the question what caused the uplift of Central Turkey. I propose to extend the scenario that was originally used to explain the rapid uplift and high elevation of Eastern Turkey to include Central Turkey. In the first part of this new scenario, following the closure of the Neotethys Ocean, the lithosphere of the Mediterranean Sea started to subduct horizontally beneath the crust of Southern Turkey but the slab continued to sink into the deeper mantle beneath Northern Turkey (Sakarya terrane). In the second part of this scenario, the subducting slab steepened and started to retreat southwards. By doing so, it removed the entire lithospheric mantle of Central and Eastern Turkey: delamination of the lithospheric mantle. I test the last part of this scenario - whether delamination can explain the uplift of Central and Eastern Turkey. Model results show that delamination of the lithospheric mantle can indeed explain the high mean elevation of Central and Eastern Turkey. Subsequently, the scenarios proposed for Eastern and Central Turkey are integrated into a single consistent evolution of entire Turkey since the Late Cretaceous at the scale of the lithosphere.
show less
