Geology of the Eastern Anatolian Plateau (Turkey): a synthesis

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The Eastern Anatolian Plateau (EAP), approximately 2000 m above sea level, is located between the Eastern Pontides to the north, the Arabian Platform to the south, and the Iranian Plateau to the east. It is characterized by approximately 6 km-thick Maastrichtian to Quaternary volcano-sedimentary cover which unconformably overlies continental and oceanic basement units. Overall, the outcrops of the pre-Maastrichtian basement are rare and include both continental and oceanic units. This led to drastically different interpretations of the nature of the pre-Maastrichtian basement as (i) the oceanic accretionary complex or (ii) continental crust and overlying ophiolitic mélange. This synthesis deals with the relationships between continental and oceanic units in light of the recent geological, geophysical, and geochemical studies. Geophysical studies consistently indicate the presence of a spatially thickened continental crust with a lateral variation ranging from 38 to 52 km. Seismological models estimate lithospheric thicknesses to be in the range of 70-80 km, suggesting the presence of a rather thinned lithosphere. The pre-Maastrichtian continental units include late Cretaceous high-T/low-P metamorphic rocks, which are intruded by late Cretaceous basic to acidic intrusions at the base. Protoliths of the high-T/low-P metamorphic rocks can be closely correlated with those of the Anatolide-Tauride Block, probably representing the metamorphosed equivalents of the Anatolide-Tauride Block. The continental crustal nature is also testified by the presence of metasyenite to -granite with igneous crystallization ages of 430-440 Ma. The Late Cretaceous ophiolitic mélanges with locally intact tracks of ophiolite and overlying forearc deposits tectonically sit over the Late Cretaceous high-T/low-P metamorphic rocks. These ophiolitic mélanges probably form part of the North Anatolian ophiolitic belt, related to the İzmir-Ankara-Erzincan suture. Maastrichtian to Quaternary volcano-sedimentary rocks overlie both the continental crustal and tectonically overlying oceanic units, representing probably collisional and postcollisional basin fills. Available geological, geochemical, and geophysical data suggest a pre- Maastrichtian basement that comprises a continental crustal domain and an overlying ophiolitic mélange beneath the Masstrichtian to Quaternary cover.