Neogen und jungtertiäre Entwicklung der Insel Kos (Ägäis,Griechenland)

The geology of the central portion of Kos island (Greece) is described. A geological map shows the distribution of the Neogene Konstantinos, Gurniati, Stefanena und Tafi formations and of the Pleistocene Plateau-tuff in the vicinity of the Dikeos mountain chain. The Neogene and Pleistocene sedimentary formations of Kos are reviewed, and a detailed sketch of the history of the island from the Miocene till now is given. The deposition of marine sediments of lower to middle Miocene age was followed by tectonic movements and accumulation of lacustrine sedimentary rocks in the upper Miocene. During that time, Kos was part of a land mass including Anatolia, the Aegean Sea and the Greek mainland. Sediments, which can be assigned to the lower Pliocene with certainty, are not known from Kos until now. From the middle Pliocene to lower Pleistocene a continuous sequence of sediments was deposited. In the lowermost lithologic units (Gurniati and Stefanena formations in central Kos, Phoka and Sefto formations in east Kos) continental sediments predominate. In central Kos, about eight marine intercalations can be traced, but the sea did not reach the eastern area. The Tafi formation (central Kos, uppermost Pliocene to lower Pleistocene) was mainly accumulated in marine environments. During the same time, in east Kos in a lake of varying size the Kos up to the Elia formations were deposited. Its endemic gastropods include some of the best examples of evolutionary lineages. When by the beginning of the Pleistocene the sea invaded this basin, the endemic fauna was destroyed. After tectonic displacement of the Plio-Pleistocene sediments, what began during accumulation of the lower Tafi formation, and after their elevation above sea-level, the area of Kos and surrounding islands was covered by the Pleistocene Plateau tuff. At about the same time, Kos became separated from the Anatolian Datça peninsula and was transformed into an island. During periods of glacial sea-level fall, however, it was more than once united with the Anatolian mainland via a northern connection. The gradual phyletic change of the freshwater snail,Melanopsis sporadum into M.gorceixi is described. The evolutionary rate was influenced by marine transgressions causing a reduction of the population size.