How to resist subduction: evidence for large-scale out-of-sequence thrusting during Eocene collision in western Turkey

Abstract

Significant along-strike variations have locked large parts of the Alpine subduction complex in the Eastern Mediterranean in the Eocene, and defined the end of high-pressure accretion in western Turkey. Structural analysis reveals that the Anatolide belt in western Turkey formed under greenschist facies metamorphic conditions in the Eocene when a high-pressure metamorphic fragment of the Adriatic plate (the Cycladic blueschist unit) was thrust onto the imbricated mid-crustal units of the Anatolian microcontinent (the Menderes nappes). The contact between the Cycladic blueschist unit and the Menderes nappes, the Cyclades–Menderes thrust, represents an out-of-sequence ramp which cuts up-section towards the south. The lack of Alpine high-pressure fabrics below the Cyclades–Menderes thrust implies c. 35 km of exhumation of the Cycladic blueschist prior to its Eocene emplacement on top of the Menderes nappes. Structure and geodynamic evolution of the Anatolide belt are in striking contrast to the neighbouring Aegean and contradict the model of a laterally continuous orogenic zone, in which the Anatolide microcontinent is interpreted as an eastern extension of the Adriatic plate.