Fission-track thermochronology of the Middle Aegean Island Bridge implications for Neogene geomorphology and palaeogeography

Abstract

43 samples from Aegean islands, Thessaly, Mt. Ossa and Pelion were investigated by apatite fission-track thermochronology. The measured cooling ages of the Cyclades and Ikaria have a distinct frequency maximum between 7 and 11 Ma (Tortonian, Late Miocene) which was a time of strong crustal extension in the south Aegean back-arc position. These ages also reflect a stage of primary peneplanation with fast denudation and intensive weathering under warm and humid conditions. The subsequent exhumation of the peneplain's weathering basal relief occurred under the drier climate of the Messinian. At least in the Cyclades and in the case of Ikaria, the development of peneplain staircase morphology could be partially caused by a step-wise sinking of the sea level in course of the Mediterranean evaporation process. However, the present-day vertical position of the peneplain torso is complicated by younger tectonical movements. The eroded material from the Middle Aegean Swell must have been trapped in proximal basins that were deep and mostly dry depressions during the Messinian. After the inundation through the Strait of Gibraltar, the Middle Aegean Swell became a large peninsula (Protokykladia) connected with Attica and Evia. It consisted of alluvial plains with active sedimentation and higher grounds inherited from the ancient peneplain.