Neogene supra-subduction zone extension in the Polis graben system, west Cyprus

Abstract

The Neotectonic Polis graben and adjacent Pegia half-graben in west Cyprus are extensional basins developed within the convergent tectonic regime 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 Polis graben structure. Evaporites were deposited in the south of the area while unconformity surfaces developed in the north. Pliocene mark and chalks were then deposited in a relatively quiescent phase in the north of the graben, 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-graben and renewed minor faulting in the Polis graben. The extensional structures of the Polis graben system are thought to result from extension above a subduction zone located south of Cyprus, driven by subduction 'roll-back' and trench migration. Accelerated convergence and rapid roll-back during Late Miocene times caused the first stage of extension, whilst the Plio-Pleistocene faulting was driven by differential extension in the overriding plate as the Eratosthenes Seamount collided with the trench and locally impeded subduction. The Polis graben system may provide a model for the early stages of development of major suprasubduction zone extensional areas such as the Aegean region.