THE HEZAN UNITS: A FRAGMENT OF THE SOUTH NEO‐TETHYAN PASSIVE CONTINENTAL MARGIN IN SE TURKEY

Abstract

Recent progress in structural and stratigraphic analysis of the allochthonous units situated north of Hazro in the Border Fold zone of SE turkey has shed light on the nature and signijicance of the Gondwanan margin there. Allochthonous material consists of several superimposed units ranging in age from the Early Trias to the Late Senonian (Hezan units), in which the transition between neritic carbonates and the pelagic and detrital facies is well indicated by an Ammonitico‐rosso facies of mid Jurassic age. Above it, ophiolitic material and radiolarites represent the former Tethyan crust and cover. The Hezan units thus belong to the former Gondwanan margin thrust southwards in Lute Cretaceous times, and a tentative reconstruction of its Mesozoic evolution there is facilitated by the absence of later major tectonic events.This reconstruction shows marked diferences compared with the more complex nearby margins described in the Hellenides or Zagrides, where parallel ridges and troughs reflect crustal extension. By contrast, the simple “staircase”geornetry of the present margin is best interpreted as the result of the fracturing of the Gondwanan continent, separating the Apulian and African Plates as early as the Trias.