The ophiolite-related Mersin Melange, southern Turkey: its role in the tectonic–sedimentary setting of Tethys in the Eastern Mediterranean region

Abstract

The Mersin Melange underlies the intact Mersin Ophiolite and its metamorphic sole to the south of the Mesozoic Tauride Carbonate Platform in southern Turkey. The Melange varies from chaotic melange to broken formation, in which some stratigraphic continuity can be recognized. Based on study of the broken formation, four lithological associations are recognized: (1) shallow-water platform association, dominated by Upper Palaeozoic–Lower Cretaceous neritic carbonates; (2) rift-related volcanogenic–terrigenous–pelagic association, mainly Upper Triassic andesitic–acidic volcanogenic rocks, siliciclastic gravity flows, basinal carbonates and radiolarites; (3) within-plate-type basalt–radiolarite–pelagic limestone association, interpreted as Upper Jurassic–Lower Cretaceous seamounts with associated radiolarian sediments and Upper Cretaceous pelagic carbonates; (4) ophiolite-derived association, including fragments of the Upper Cretaceous Mersin Ophiolite and its metamorphic sole. Locally, the ophiolitic melange includes granite that yielded a K/Ar radiometric age of 375.7±10.5 Ma (Late Devonian). This granite appears to be subduction influenced based on ‘immobile’ element composition.

The Mersin Melange documents the following history: (1) Triassic rifting of the Tauride continent; (2) Jurassic–Cretaceous passive margin subsidence; (3) oceanic seamount genesis; (4) Cretaceous supra-subduction zone ophiolite genesis; (5) Late Cretaceous intra-oceanic convergence-metamorphic sole formation, and (6) latest Cretaceous emplacement onto the Tauride microcontinent and related backthrusting.

Regional comparisons show that the restored Mersin Melange is similar to the Beyşehir–Hoyran Nappes further northwest and a northerly origin best fits the regional geological picture. These remnants of a North-Neotethys (Inner Tauride Ocean) were formed and emplaced to the north of the Tauride Carbonate Platform. They are dissimilar to melanges and related units in northern Syria, western Cyprus and southwestern Turkey, which are interpreted as remnants of a South-Neotethys. Early high-temperature ductile transport lineations within amphibolites of the metamorphic sole of the Mersin ophiolite are generally orientated E–W, possibly resulting from vertical-axis rotation of the ophiolite while still in an oceanic setting. By contrast, the commonly northward-facing later stage brittle structures are explained by backthrusting of the ophiolite and melange related to exhumation of the partially subducted northern leading edge of the Tauride continent.