Mesozoic extensional history of the southern Tethyan continental margin in the SE Aegean

The islands of Rhodes, Alimnia and Symi are situated at the eastern end of the Hellenic arc. Well exposed on these islands are a series of nappes composed of Mesozoic-early Tertiary, principally carbonate, sequences which formed the sedimentary cover of the southern Tethyan margin and were stacked during Alpine deformation in the late Palaeogene. The stratigraphy of these sequences is described and interpreted as preserving a transition from a carbonate platform through slope to basin. The sequences formed part of the cover of a passive continental margin but this margin differed from typical modern margins in recording several episodes of extension with no clear evidence of ocean crust formation in the SE Aegean. Three important episodes of extension are recorded: a platform-basin topography was initiated by Mid-Late Triassic rifting, late Liassic extension led to platform collapse and development of carbonate slopes, and renewed Late Cretaceous extension further reduced the size of carbonate platforms. The Late Cretaceous extension was probably linked to the formation of ocean crust further east, in Cyprus and Turkey. Sedimentological evidence indicates that the slope was eastward-facing and the platform-basin margin was orientated approximately north-south. This evidence is not consistent with previously proposed palaeogeographic reconstructions of the region based on tracing the isopic zones of the Hellenides through the arc. A new two-dimensional reconstruction of the form of the southern Tethyan margin in the SE Aegean is proposed.