Formation and emplacement ages of the SSZ-type Neotethyan ophiolites in Central Anatolia, Turkey: palaeotectonic implications

Abstract

Isolated outcrops of ophiolitic rocks, termed the Central Anatolian Ophiolites, are found as allochthonous bodies in the Central Anatolian Crystalline Complex, that represent the metamorphosed passive northern edge of the Tauride–Anatolide Platform, central Turkey. In terms of pseudostratigraphic relationships of the magmatic units and their chemical designation, the Central Anatolian Ophiolites exhibit a supra-subduction zone (fore-arc) setting within the Vardar–İzmir–Ankara–Erzincan segment of the Neotethys. The epi-ophiolitic sedimentary cover of the Central Anatolian Ophiolites is generally characterized by epiclastic volcanogenic deep-sea sediments and debris flows intercalated with pelagic units. The richest and most significant planktonic foraminiferal association recorded from the lowest pelagic members infer a formation age of early–middle Turonian to early Santonian. K/Ar ages of post-collisional granitoids (81–65 Ma) intruding the basement rocks as well as the Central Anatolian Ophiolites suggest a post-early Santonian to pre-middle Campanian emplacement age. The marked high volume of epiclastic volcanogenic sediments intercalated with the pelagics of the Central Anatolian Ophiolite is suggestive of rifting in a marginal sea adjacent to a volcanic arc. Penecontemporaneous tectonism is reflected in repetitions in the stratigraphy and in debris flows, which result from major slides and mass-gravity reworking of pre-existing units and of arc-derived volcanics and sediments. Correlating the rock units and formation/obduction ages of the Central Anatolian Ophiolites with further supra-subduction zone type ophiolites in the eastern (Turkey) and western (Greece) parts of the Vardar–İzmir–Ankara–Erzincan segment of Neotethys we conclude that the intraoceanic subduction in the east is definitely younger and the closure history of this segment is more complex than previously suggested. Copyright © 2000 John Wiley & Sons, Ltd.