Geology and structural evolution of the Tokat Massif (Eastern Pontides, Turkey)

Abstract

The Tokat Massif consists of a pre-Jurassic metamorphic complex that crops out widely between Amasya and Resadiye in the western part of eastern Pontides, and which can be correlated with the Karakaya Complex of the western Pontides. This complex is named the Tokat Group, and is divided into two main units, namely, the Turhal Metamorphics and Devecidag Melange. The Turhal Metamorphics form a volcano-sedimentary sequence in the northern part of the Tokat Massif. The lower level of the formation is made up of gneiss, amphibolite and mica schists, whereas the upper part is represented by an alternation of mica schist, phyllite, metaclastic rocks, metabasite and marble, which probably reflects an arc association. The Devecidag Melange is characterised by a metavolcano-sedimentary olistostrome, which forms the southern part of the massif. This unit is quite heterogeneous and reflects, in places, a subduction melange and/or a fore-arc sequence. The Devecidag Melange may have formed in a setting between a subduction zone and a fore-arc. The units of the Tokat Massif can be traced along the eastern Pontides and also along the North Anatolian Ophiolitic Belt. These units have been accreted to the melange prism as tectonic slices along the North Anatolian Ophiolite Belt before the Campanian. Some of Late Cretaceous ophiolitic melange slices also crop out in the Tokat Group as E-W-trending tectonic slices. The ophiolites and ophiolitic melange are believed to have been emplaced both to the north and to the south during the Late Cretaceous. The north-vergent thrusts have been later realigned into south-dipping thrusts during a neotectonic phase.