International Geological Journal - Official Journal of the Carpathian-Balkan Geological Association

New age data from the tectonostratigraphic units of the Istranca “Massif” in NW Turkey: a correlation with SE Bulgaria

Pages: 255 - 277

Authors: YAVUZ BEDI, EMIL VASILEV, CHRISTO DABOVSKI, ALI ERGEN, CENGIZ OKUYUCU, ADIL DOGAN, U. KAGAN TEKIN, DARIA IVANOVA, ILIANA BONCHEVA, ISKRA LAKOVA, VALERI SACHANSKI, ISMAIL KUSCU, ERCAN TUNCAY, D. GÜLNUR DEMIRAY, HAVVA SOYCAN, M. CEMAL GÖNCÜOGLU

Abstract: The Istranca Crystalline Complex in NW Anatolia and SE Bulgaria includes structural units that differ in lithostratigraphy, metamorphism, age and structural position. They are collectively named as the “Istranca nappes” comprising from bottom to top the Sarpdere, Mahyada˘g and Do˘ganköy Nappes. The Sarpdere Nappe consists of Lower Triassic arkosic metasandstones with slate interlayers, followed by Middle to Upper Triassic carbonates and an alterna- tion of Upper Triassic clastics and carbonates. The Mahyada˘g Nappe comprises a low-grade metamorphic Late Paleo- zoic—Triassic carbonate-siliciclastic sedimentary succession. The Do˘ganköy Nappe includes Precambrian?—Paleozoic metasediments, intruded by Late Carboniferous-Early Permian calc-alkaline granitoids. Its Triassic cover comprises metaclastics and metacarbonates. The Istranca nappes were juxtaposed at the end of the Triassic and transgressively covered by Lower Jurassic coarse clastics, followed above by Middle to Late Jurassic carbonates, black shales and carbonate-siliciclastic sedimentary succession. The phosphate concretions in black shales yielded radiolarian assem- blages indicating Late Bajocian-Early Bathonian, Early Bathonian and Early Kimmeridgian ages. These nappes and their Jurassic cover are unconformably overlain by the Cenomanian-Santonian volcano-sedimentary successions in- truded by Santonian-Campanian Dereköy-Demirköy intrusive suite. The preliminary data suggest that the Variscan basements of the Mahyada˘g and Sarpdere Nappes were juxtaposed prior to the Triassic and overridden by the Do˘ganköy Nappe of possible Rhodopean origin from S to N during the Cimmerian compressional events.

Keywords: NW Turkey, SE Bulgaria, Istranca Crystalline Complex, stratigraphy, nappes

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