Diagenetic and very low-grade metamorphic characteristics of the Paleozoic series of the Istanbul Terrane (NW Turkey)

Bozkaya, Omer
Göncüoğlu, Mehmet Cemal
The Istanbul Terrane along the Black Sea coast in NW Anatolia, is a Gondwana-derived continental microplate, comprising a well-developed Paleozoic succession. Petrographic and X-ray diffraction studies were performed on rock samples from measured sections throughout Ordovician-Carboniferous sedimentary units. Diagenetic-very low-grade metamorphic clastic (shale/mudstone, siltstone, sandstone) and calcareous rocks (limestone, dolomite) mainly contain phyllosilicates, quartz, feldspar, calcite, dolomite, hematite and goethite minerals. Phyllosilicates are primarily represented by illite, chlorite, mixed-layered chlorite-vermiculite (C-V), chlorite-smectite (C-S) and illite-chlorite (I-C). Feldspar is commonly present in the Ordovician and Carboniferous units, whereas calcite and dolomite are abundant in the Silurian and Devonian sediments. The most important phyllosilicate assemblage is illite + chlorite + I-C + C-V + C-S. Illite and chlorite-bearing mixed layer clays are found in all units. The amounts of illites increase in the upper parts of the Silurian series and the lower parts of the Devonian series, whereas chlorite and chlorite-bearing mixed-layers are dominant in the Ordovician and Carboniferous units. Kubler index values of illites reflect high-grade anchimetamorphism for the Early Ordovician rocks, low-grade metamorphism to high-grade diagenesis for the Middle Ordovician-Early Silurian rocks and high-grade diagenesis for the Late Silurian-Devonian units. The K-white micas b cell dimensions indicate intermediate pressure conditions in the Early Ordovician-Early Silurian units, but lower pressure conditions in the Middle Silurian-Devonian units. Illites are composed of 2M(1) +/- 1M(d) polytypes in all units, except for Upper Ordovician-Lower Silurian units which involve 1M polytype in addition to 2M(1) and 1M(d) polytypes. The 2M(1)/(2M(1) + 1M(d)) ratios rise from Devonian to Ordovician together with the increasing diagenetic-metamorphic grade. Chlorites have IIb polytype. In general, crystal-chemical data of clay minerals in the Istanbul Terrane show a gradual increase in the diagenetic/metamorphic grade together with increasing depth. The new data presented in this work indicate that the diagenetic/metamorphic grade of the Paleozoic of the Istanbul Terrane is higher than that of the neighboring Zonguldak Terrane and generated by a single metamorphic phase developed at the end of Carboniferous. This finding contrasts with the metamorphic history of the neighboring Zonguldak Terrane that displays a distinct Early Devonian unconformity and a thermal event.


Mineralogic evidences of a mid-Paleozoic tectono-thermal event in the Zonguldak terrane, northwest Turkey: implications for the dynamics of some Gondwana-derived terranes during the closure of the Rheic Ocean
Bozkaya, Omer; YALÇIN, HÜSEYİN; Göncüoğlu, Mehmet Cemal (2012-04-01)
The Zonguldak terrane is a Gondwana-derived continental microplate along the Black Sea coast in northwest Anatolia. It includes a Cadomian basement, with oceanic-and island-arc sequences, unconformably overlain by siliciclastic rocks of Ordovician to Middle Silurian age. After a period of deformation and erosion, late Lower Devonian (Emsian) quartzites and shallow-marine limestones unconformably cover Middle Silurian (Wenlock) graptolitic shales. Along several cross sections across the unconformity plane, t...
TOPRAK, V; Göncüoğlu, Mehmet Cemal (1993-12-01)
The Neogene-Quaternary Central Anatolian Volcanic Province (CAVP) is elongated in a north-east south-west direction within pre-Oligocene basement in central Turkey. This study investigates the field evidence relating to the development of the CAVP.
Holocene paleoenvironmental evolution of the Acıgöl paleo maar lake (Nevşehir, Central Anatolia)
Tuncer, Alaettin; Tunoğlu, Cemal ; Aydar, Erkan ; Yılmaz, İsmail Ömer; Gümüş, Burçin Aşkım ; Şen, Erdal (2019-12-01)
Acıgöl (Nevşehir, Central Anatolia) is a drained crater lake. Acıgöl maar was formed by the violent vapor explosions due to the interaction of hot rhyolitic magma with the (sub-)surface water during the latest Pleistocene. A 844 cm-deep borehole was drilled at the maar and 713 cm-thick Acıgöl Core Succession (ACS) was retrieved. The ACS is mainly composed of lower laminated and upper non-laminated mudstones (sandy, silty, and clayey) with rare organic and volcanic interlayers. Eleven ostracod taxa (Cypris p...
Episodic, two-stage Neogene extension and short-term intervening compression in Western Turkey: field evidence from the Kiraz Basin and Bozdag Horst
Bozkurt, Erdin (2005-05-01)
Western Anatolia (Turkey) is a region of widespread active N-S continental extension that forms the eastern part of the Aegean extensional province. The extension in the region is expressed by two distinct/different structural styles, separated by a short-term gap: (1) rapid exhumation of metamorphic core complexes along presently low-angle ductile-brittle normal faults commenced by the latest Oligocene-Early Miocene period, and; (2) late stretching of crust and, consequent graben evolution along Plio-Quate...
Metamorphism in the Palaeozoic schists of the Southern Menderes Massif field petrographic textural and fabric data from Selimiye Milas Muğla area
Bozkurt, Erdin (1996-01-01)
Abstract: The Menderes Massif is a large-scale metamophic core-complex in western Anatolia and forms the western of two large metamorphic culminations in the Turkish Alpide orogen. Within the Southern Menderes Massif on the southern side of the Beßparmak Mountain north of Selimiye (Milas-MuÛla), two distinct lithologic groups are recognized on the basis of their lithology and structural position: the late Oligocene granitoid rocks now in the form of mylonitic augen gneiss and the structurally overlying sequ...
Citation Formats
O. Bozkaya, H. YALÇIN, and M. C. Göncüoğlu, “Diagenetic and very low-grade metamorphic characteristics of the Paleozoic series of the Istanbul Terrane (NW Turkey),” SWISS JOURNAL OF GEOSCIENCES, pp. 183–201, 2012, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/32063.