Tectono-stratigraphic reconstruction of the Keban metamorphites based on new fossil findings, Eastern Turkey

Abstract

Keban metamorphites located at the orogenic belt of the Eastern Taurides is an allochtonous union metamorphized at the greenschist facies comprised of several nappes. Contrary to the massives around it, the aging of the union is not quite satisfactory due to the lack of fossil data. Permo-Triassic/Permo-Carboniferous ages have been used until now for the age of the metamorphites that are stated to be located only at a single location, the species of which have not been determined and which are based on two fossil data. However, for the first time in this study, “microgastropods” have been found at Early Triassic age related with The Great Dying at the end of the Permian inside the clastic limestones at the base levels of the Nimri Formation which is one of the lower nappes of the Keban metamorphites. Again, trace fossils Planolites, Rhizocorallium, Thalassinoides, Helminthopsis and (?)Protovirgularia have been determined for the first time in the layered crystallized limestones at the medium levels of the Nimri Formation. This ichnofabric is frequently observed in the Middle Triassic aged limestones at Germany, Poland, Austria, Italy and the Taurides and is known as the “vermicular limestone facies”. The ages of Keban marble, Delimehmet and Süleymanlı Formations, tectonically located on the Nimri Formation, are evaluated by regional correlations as Middle-Late Devonian, Late Devonian and Early Carboniferous, respectively. In addition, probably pre-Triassic aged, dark green colored metadiabase dykes have been inserted in the Delimehmet formation in relation with the Variscan Orogeny. Regional correlations with other units and massives indicate that the Keban metamorphites that have deposited at the farthest north of the south branch of the Neo-Tethys ocean paleogeographically may be the continuation of the Bolkardağı Union at the east rather than the Alanya and Geyikdağı Unions. © 2016 Elsevier Ltd