Palaeorotation of the Troodos microplate, Cyprus

Abstract

The Troodos ophiolite represents one of the best preserved fragments of ocean-floor crust that is exposed on land. As the extrusive series of the ophiolite retains a stable magnetization that is directed westward, the ocean crust is considered to have rotated anticlockwise through 90° since its formation in the Late Cretaceous1. To determine the timing of the rotation event, over 3,000 orientated samples have been collected from the ophiolite and from its in situ Turonian to Recent sedimentary cover. Here we report that pelagic chalks immediately overlying the highest extrusive lava units of the ophiolite complex give reliable magnetic vector directions indicating that at least 60° of rotation occurred before the Lower Eocene and that rotation was completed by the end of the Lower Eocene. Rotation cannot have occurred within a single late Miocene event, as reported previously2. Regional geological considerations support the rotation of only a small fragment of oceanic crust that was stranded adjacent to an active continental margin. In this tectonic setting the oblique consumption of oceanic crust beneath Troodos crust could provide the necessary driving force for tectonic rotation.