The Ophiolitic Molasse Unit of Ikaria Island (Greece)


Abstract: Ikaria Island can be divided generally into two composite tectonic units, namely the lower and upper. The lower unit comprises paragneiss basement with local orthogneiss bodies that is overlain by a platform-type marble sequence, passing upward into a sequence of intercalated schist and marble that is intruded by Miocene granites. The upper unit has not experienced Alpine high-pressure metamorphism, and is restricted to the central (Kefala unit) and northeastern (Faros area) parts of the island, which host ophiolitic associations similar to those found in the upper unit of several Cycladic islands. The Faros area consists of an Oligocene-Early Miocene age ophiolitic molasse unit (conglomerates and olistostromes), rich in ophiolitic clasts, which are similar to diorite and amphibolite rocks of the Kefala unit, and probably were derived from Late Cretaceous oceanic crust. Furthermore, olistolites and/or rifted recrystallised carbonate blocks that are similar to those of the Kefala unit overlie the upper parts of the molasse unit, which elsewhere is discordantly succeeded by Lower Pliocene marine formations. Therefore, the tectonic emplacement of the upper unit is assigned to the Late Miocene. The origin and provenance of the molasse unit is probably the present Cretan Basin. Thus, in its northwestern part, the molasse unit is related to the Eocene-Miocene molasse of the Meso-Hellenic trough of continental Greece, to the northeast passes into the SW Anatolian Late Oligocene-Early Miocene molasse basin of Turkey.

Keywords: Olistostrome, ophiolite, Cretaceous, molasse, Miocene, Ikaria, Cyclades, Greece

Full Text: PDF