GEOLOGY OF THE KÜTAHYA-BOLKARDAĞ BELT

Abstract

Kütahya-Bolkardağ Belt is one of the subunits of the Tauride-Anatolide Terrane extending from the Aegean Sea to the Hınzır Mountains. It includes numerous tectonic slices, formed during the closure of the İzmirAnkara Oceanic branch of the Neotethys. The tectonic slices are mainly derived from three different tectonic settings: i- rocks representing the oceanic lithosphere and subduction- accretion prism of the İzmirAnkara Ocean (ophiolites and ophiolitic mélanges), ii- flysch-type deposits that were formed in foreland-basins on the northern and passive edge of the Tauride-Anatolide platform in front of the southward advancing nappes (olistostromes with olistoliths, sedimentary mélanges), and iii- successions, in some cases with HP/LT metamorphism, representing the slope margin and external platform of the northern Tauride-Anatolide margin. Rock-units of the Kütahya-Bolkardağ Belt surround the HT/LP Menderes Core Complex and are also observed as slices or klippen in the massif, or as nappes to the south of it. The rocks of the İzmir-Ankara oceanic lithosphere occur as huge allochthonous bodies/tectonic slices and blocks within the mélange and olistostromes. The fossil data and geochemical data obtained suggest the following: The earliest "oceanic" volcanism commenced during middle Carnian, the generation of ocean island-type (OIB) volcanics lasted from Bajocian to Abtian, where as the MORbasalts spread from Aalenian to Turonian. Supra-subduction- and island-arc type basalts of Albian to Cenomanian age indicate an intra-oceanic subduction within the İzmir-Ankara Ocean. The mélanges are characterized by HP/LT metamorphism with a LP/LT overprint. Middle Maestrichtian olistostomes with olistoliths formed in foreland basins in front of the nappes include blocks of all kind of tectonic settings mentioned above. The flysch rocks are in depositional contact with the underlying platform and/or slope rocks of the Tauride-Anatolide passive margin. The Tauride-Anatolide slope and external platform deposits are partly affected by HP/LT metamorphism and occur as slices along the belt and as blocks within the flysch-basins. In Afyon area the Late Permian transgresses onto the Precambrian basement, whereas in Konya, more internal in regard to the platform, the Devonian carbonate platform is drowned and covered by back-arc-type sediments and volcanism of Carboniferous age. All along the belt, early Late Permian unconformably covers a slightly metamorphosed and deformed basement, attributed to a Variscan event within the Tauride-Anatolide platform. The Lower Triassic sequences unconformably covering the older units and starting with volcanogenic continental clastics, pass into the marine carbonates by Anisian. In the allochtonous belonging to the more internal platform, the Ladinian-Lower Cretaceous sequences are represented with thick platform carbonates. The first deep marine sediments take place in some slices of these sequences which is interpreted as the initial rifting of the İzmir-Ankara oceanic branch. While only the slope sediments accompanying with transitional ocean crust volcanics are observed in the allochtonous derived from the northernmost part of the Taurid-Anatolid platform, the Ladinian-Lower Cretaceous sequences are represented by thick platform carbonates in the allochtonous of the inner platform. The transition from platform to slopetype deposits is in Malm in the allochtonous of the external platform, but Abtian in more internal parts. This indicates a stepwise deepening of the platform-margin. The presence of HP/LT metamorphic platform-margin sediments is indicative for a deep subduction of the attenuated continental-crust of the Tauride-Anatolide margin. The initial compression-slicing and nappe-emplacement must have realized prior to Middle Paleocene. Middle Paleocene-Middle Eocene in the Kütahya-Bolkardağ Belt is characterized by shallow-marine or continental molasse-type deposition in the remnant basins on the platform.