Cold Tectonics of Kos, Central Dodecanese: Oligocene Bivergent Extension of the Pelagonian Domain

Abstract Tectonic and lithological correlations between the Cycladic Blueschist Unit of the Aegean domain and Pelagonian domain of the western Turkey have rarely been proposed. Herein, we focus on the pre‐volcanic geology of Kos, and investigate the tectonic history of the central Dodecanese Islands and the general correlation between the two domains. Raman Spectroscopy of Carbonaceous Material analyses combined with white mica 40 Ar/ 39 Ar and zircon (U‐Th)/He geochronology were carried out to determine peak temperatures and the timing of tectonothermal events recorded by the various units. Three tectonic units were identified: (a) the Dikeos Unit including the Paleozoic Unit overlain by the Permo‐Triassic Wildflysch Unit, whose rocks have reached a maximum temperature of 300°C; (b) the Marina Basement Unit was thrusted onto the Dikeos Unit with top‐to‐N kinematics during the Paleocene, reaching a maximum temperature of 565°C; (c) the Marina Cover Unit is preserved as isolated klippen juxtaposed onto the Dikeos Unit along the Oligocene top‐to‐SSE Kos Detachment. The Dikeos Unit was then intruded by a c. 10 Ma monzonite, creating a few hundred meters wide metamorphic aureole. At the regional scale, we propose that units from Kos belong to the Pelagonian domain and that post‐orogenic N‐S bivergent extension started in the Oligocene. Over the same time, the deformation started to propagate to deeper structural levels affecting the rocks of the Cycladic Blueschist Unit. Unfortunately, the lack of consensus on the deformation history in southwestern Turkey does not unequivocally allow the constraints to be extended eastward. Finally, mid‐Neogene to recent extension continues within a consistent N‐S direction, which is related to slab retreat and tearing.