GEOLOGY, CORRELATION AND GEODYNAMIC EVOLUTION OF THE MERSIN MéLANGES, SOUTHERN TURKEY

Extensive field work and numerous micropaleontological determinations in the infra-ophiolitic mélanges of the Mersin ophiolite (Southern Turkey) lead us to clearly differentiate two mélanges: the Late Cretaceous Sorgun Ophiolitic mélange and the Ladinian-Carnian Hacialaný mélange. We show that these mélanges display the mixed origin of different blocks and broken formations, as summarized below.

(1) The Paleotethyan remnants are common and found exclusively in the Hacialaný mélange as small blocks and few broken formations. Pennsylvanian and Early Permian slope and basin deposits (calcarenites, radiolarites) are unknown from the western Neotethys but were already described in Paleotethyan series in the Lycian Nappes and in the margins of displaced terranes in Iran. Radiolarites of Kungurian age are sometimes associated with large amount of tuffites and are also unknown in the western Neotethyan realm, where the oldest radiolarites have a (late) Wordian age. Kungurian radiolarites and pelagic limestones on tuffs and volcanics are common in the Paleotethys of Iran, where they are related to Early Permian seamounts within the Paleotethys. These Paleotethyan remnants within the HM were most likely reworked as major olistostromes in the Neotethys basin during the Eo-Cimmerian orogenic event.

(2) Neotethyan elements are represented by potential Middle-Late Triassic seamounts and by broken formations containing Neotethyan faunas. The rich occurrence of Metapolygnathus mersinensis Kozur & Moix and M. primitius sensu stricto in the latest Carnian of the Kocatabur block, as well as the rich occurrence of the middle Norian Epigondolella praeslovakensis Kozur, Masset & Moix in the Gâvuruçtugu block indicate a derivation from the Neotethys, but further studies in the latest Carnian to middle Norian interval of the Pindos, Antalya and Huglu units are necessary to exclude the common occurrence of these two species in the Huglu-Pindos Ocean to which belong also the Antalya Nappes.

(3) The main Anatolian elements (upper plate position) are symbolized by sequences belonging to the northern passive margin of the Anatolian terrane (southern margin of the Huglu-Pindos Ocean), outlined by the Late Triassic syn-rift volcanic event (Huglu-type series also found in the Beyþehir-Hoyran Nappes), the early flexuration of the margin (already during the Cenomanian) and the Late Cretaceous obducted ophiolitic sequences. This margin is interpreted as emerging from the collapse of the former Variscan cordillera and opening of major back-arc type basins along the northern active margin of Paleotethys during the Triassic.

(4) The Tauric elements (lower plate position) are represented by Eo-Cimmerian flysch-like and molasse sequences, intercalated in Neotethyan series starting most probably with pelagic Permian sediments totally absent in the Anatolian domain. Other blocks are most probably derived from the parautochthonous sequences belonging to the Taurus-Beydaglarý marginal sequences.

The Mersin Ophiolitic Complex belongs to the South-Taurides Exotic Units, extending from Mersin to Antalya, and which can be widened to the Mamonia “Nappes” in Cyprus. This domain is made of exotic elements of the Anatolian terrane now found south of the Taurus terrane, juxtaposed to elements derived from the Paleotethys/Neotethys/Taurus terrane, and emplaced onto the Taurus southern margin (Mersin) or Beydaglarý domain (Antalya) in Late Cretaceous-Paleocene times. In term of paleotectonic and paleogeography, a direct implication is the need of (roughly E-W) lateral displacements of hundred kilometers scale to explain the present day structural scheme. In conclusion, the ages and distribution of the basin, slope and platform facies found in the mélanges, their faunistic content, the age of the passive margin onto which the ophiolites were obducted, and the evolution of the stratigraphic series demonstrate that several Tethyan oceanic basins were involved in the formation of the southern Tauric ophiolitic nappes. The coexistence south of the Bolkardag of these cosmopolitan units is of crucial importance to decipher the regional paleogeographic and paleotectonic evolution.