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

Abstract

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, Mahyadag and Doganköy Nappes. The Sarpdere Nappe consists of Lower Triassic arkosic metasandstones with slate interlayers, followed by Middle to Upper Triassic carbonates and an alternation of Upper Triassic clastics and carbonates. The Mahyadag Nappe comprises a low-grade metamorphic Late Paleozoic-Triassic carbonate-siliciclastic sedimentary succession. The Doganköy 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 assemblages 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 intruded by Santonian-Campanian Dereköy-Demirköy intrusive suite. The preliminary data suggest that the Variscan basements of the Mahyadag and Sarpdere Nappes were juxtaposed prior to the Triassic and overridden by the Doganköy Nappe of possible Rhodopean origin from S to N during the Cimmerian compressional events.

The phanerozoic palaeotectonics of Turkey. Part I: an inventory

“…2) we drew the lower surface shown in the stereogram, because the upper surface shows the rocks expelled from suture in the form of nappes that cover the continental fragments usually on the downgoing plate, but, much more rarely, also on the overlying plate and mask their true extent and dark shales, equivalents of the Palaeokastro Formation in Bulgaria (Chatalov 1992). Their ages are Lower to Middle Triassic (Chatalov 1992;Hagdorn and Göncüoğlu 2007;Bedi et al 2013). A Jurassic sequence following them sits on them across a mylonitic zone.…”

Triassic limestone, turbidites and serpentinite–the Cimmeride orogeny in the Central Pontides

“…1). In the west in the Balkans the Triassic sediments were deposited on a continental to shallow marine platform passing to a deep shelf or platform margin at Dobrugea and Istanbul (Gedik, 1975; Muttoni et al 2000; Seghedi, 2001; Derman, 2002; Bedi et al 2013). They rest unconformably on the eroded remnants of the Variscan orogen, which include deformed Carboniferous sedimentary rocks and Permo-Carboniferous granitoids.…”

Two-Stage Late Jurassic to Early Cretaceous Hydrothermal Activity in the Sakar Unit of Southeastern Bulgaria

“…The Sakar Unit of the Strandja Zone [13], also known as the Strandja (Strandzha) Massif (SM; [14,15] and references therein) or Istranca Massif (IM; [16]), is located in the southeastern part of Bulgaria, close to the border with Turkey and Greece ( Figure 1A). It belongs to the East Srednogorie Zone of the Balkan Orogenic System [17,18].…”