NEOGENE SUPRA-SUBDUCTION ZONE EXTENSION IN THE POLIS GRABEN SYSTEM, WEST CYPRUS

The Neotectonic Polls graben and adjacent Pegia half-graben in west Cy prus are extensional basins developed within the convergent tectonic r egime of the Eastern Mediterranean. Both basins contain an early fill of Miocene carbonates including reef limestones. Messinian extension, oriented ENE-WSW, produced the asymmetrically faulted Polls graben str ucture. Evaporites were deposited in the south of the area while uncon formity surfaces developed in the north. Pliocene marls and chalks wer e then deposited in a relatively quiescent phase in the north of the g raben, while faulting continued into the Early Pliocene in the south. Plio-Pleistocene to Recent sediments record regional uplift of Cyprus. Contemporaneous NNE-SSW-oriented extension formed the Pegia half-grab en and renewed minor faulting in the Polls graben. The extensional str uctures of the Polls graben system are thought to result from extensio n above a subduction zone located south of Cyprus, driven by subductio n 'roll-back' and trench migration. Accelerated convergence and rapid roll-back during Late Miocene times caused the first stage of extensio n, whilst the Plio-Pleistocene faulting was driven by differential ext ension in the overriding plate as the Eratosthenes Seamount collided w ith the trench and locally impeded subduction. The Polls graben system may provide a model for the early stages of development of major supr a-subduction zone extensional areas such as the Aegean region.