Türkiye Jeoloji Bülteni

Abstract: The Gediz Graben basin, one of the youngest and important structural elements of the Western Anatolia,has an evolutionary history with markedly geologic and geomorphologic phases during the Quaternary.The old and actual Gediz River, running since the beginning of the Quaternary, and various sized lakehave deposited their sediments during a tectonic-controlled basin evolution processes developed in N-Sextension regime.In this study, sedimentary facies, environmental properties and characteristics of the Gediz basin changedby synsedimentary tectonics during the early and late Quaternary are explained. Also it is emphasized thatthe joining adventure of the river with the sea was probably lived in the middle of the Holocene, and thegeologic and geomorphologic evolution of the river in the Quaternary is interpreted.

Abstract: The Devonian metasandstones from allocthonous Bolkardağı Unit outcropping in Central (BozkırKonya, İsalı formation Gerez member) and Eastern (Kangal-Sivas, Kangal formation Bakırtepemember) Taurides mainly include quartz (monocrystalline and polycrystalline), feldspar (microclineand plagioclase), phyllosilicate (illite, chlorite, C-V, C-S and dickite) and rock fragments (phyllite andquartzite). Polycrystalline quartz, microcline and phyllitic rock fragments found as higher amounts inthe Bakırtepe member, but plagioclase in the Gerez member. The metasandstones are represented bya composition of quartz arenite in the Gerez member, whereas of subarkose in the Bakırtepe member.Devonian metasandstones have differences such as lithologic (dominance of sand-size siliciclastic rocks)and mineralogic (more feldspar and quartz, appearance of 1M illites, different phyllosilicate assemblages)with respect to overlying and underlying units with same age. Metasandstones were characterized by highcontents of SiO2, Al2O3, Fe2O3 and K2O, and Bakırtepe member is rich in K2O but poor in CaO ana Na2Oin comparison with those of the Gerez member depending on feldspar types. Bakırtepe and Gerez membersare separated from one another and fed largerly from both sedimentary and magmatic sources accordingto the ratios of chondrite-normalized trace elements. As a conclusion; The members of Bolkardağı Unithave the same age and similar stratigraphic setting and lithologies, hovewer some important differenceswith respect to their sources, sedimentations and diagenetic/metamorphic histories. These differenceswere evaluated as sudden changes in provence through transgression related to Variscan orogeny peculiarto northern units of Taurides rather than continuous sedimentation.

Abstract: The aim of the presented study is to review the ophiolites and ophiolitic mélanges of Turkeyand their importance for constraints on the evolution of the region. On the basis of the existing data, theophiolitic associations of Turkey are classified in three main groups.

1. Group comprises pre-Alpine ophiolites and mélanges located on the southern edge of theIstanbul zone. These associations are in Pre-Jurassic age, and represent ophiolitic sequences of the PontideSuture zone. The Karakaya complex represents pre-Alpine ophiolitic mélange and developed during theemplacement of the pre-Alpine ophiolites. The opening and closing ages and polarity of the Paleotethysis still a question. 

2. Group can be divided in two sub-belts and they are the Northern-Northeastern and the Southernsub belt. They are allied to the North Anatolian Ophiolitic Belt (NAOB). The northern-northeastern subbelt extends from Izmir to eastward, continuing as the Ankara-Erzincan zone and as the Sevan-Akerasub-belt of the Lesser Caucasus Ophiolitic Belt (LCOB). This sub-belt directly represents the northernbranch of Neotethys. The ophiolites of this sub-belt represent dismembered ophiolitic sequences andtake place within the Late Cretaceous melanges. The southern sub-belt begins in the Marmaris area andcontinues eastward to the Hadim, Aladağlar, Tecer-Divriği, Erzurum, Kağızman areas, and then on to theVedi sub-belt of the LCOB. The ophiolitic outcrops of the Hınıs area and northeast of Lake Van, may bethe southernmost products of the southern sub-belt of the NAOB associations. In the framework of age,composition, and tectonic setting ophiolites and mélanges of the southern sub-belt and northern sub beltshow similar characteristic features. Therefore the southern subbelt units may be tectonically transportedproducts of the northern sub-belt. The opening of the northern branch of Neotethys began in Triassic timein the west, in the Jurassic in the east. The closing of the northern branch of Neotethys was initiated in theLate Cretaceous and ended in pre-Middle Eocene time.

3. Group is represented by the Southern and Southeastern Anatolian Ophiolitic Belt (SAOB) comprisingJurassic-Lower Cretaceous ordered ophiolitic sequences and Late Cretaceous mélanges. Opening of the southern Neotethys began in Triassic and closure began in the Late Cretaceous and ended in pre-LateMiocene.

2. and 3 groups of ophiolites with mélanges are separated from one another by the Taurus UnmetamorphicAxis of the Anatolide-Tauride block These ophiolites together include Mid Ocean Ridge Basalt (MORB)and Supra-subduction zone (SSZ) type ophiolites, emplaced along double northward subduction zones inLate Cretaceous. The emplacement style for the ophiolitic units along NAOB and SAOB show a flowerstructure, on the basis of the presence of north- and south-facing overthrusts.