Late Telychian (early Silurian) graptolitic shales and the maximum Silurian highstand in the NW Anatolian Palaeozoic terranes

Sachanski, Valeri; Göncüoğlu, M. Cemal; Gedik, İbrahim

doi:10.1016/j.palaeo.2010.03.011

Cited by 18 publications

(11 citation statements)

References 24 publications

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“…These differences cannot be explained simply by lateral facies changes; hence, they were considered (Göncüoglu et al 1997) as two different Variscan terranes. In the Safranbolu area of the ZT, Paleozoic successions include a low-grade angular unconformity between Wenlock graptolitic shales (Sachanski et al 2010) and late Early Devonian (Emsian) (Göncüoglu et al 2004) carbonates. On the contrary, IT is characterized by continuous deposition during the same time interval.…”

Section: Introductionmentioning

confidence: 99%

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

2012

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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, the mineralogical characteristics of the Paleozoic sedimentary rocks in the Zonguldak terrane are studied to check whether this regional unconformity is only of epeirogenic nature or the result of a thermal event. In addition to the appearance of kaolinite in Devonian units, crystal-chemical data of illites show a sudden jump at the unconformity plane. The b cell dimension values of illites of Ordovician–Silurian units are somewhat higher than those of Devonian–Carboniferous units and show a drastic drop between the Silurian and Devonian units. The new mineralogic data indicate that the pre-Emsian rocks in the Zonguldak terrane experienced a thermodynamo event, prior to the Emsian transgression. This Caledonian-time event is also reported in east Moesian terrane but not noticed in the neighboring Istanbul–Zonguldak and in the west Moesian – Balkan – Kreishte terranes. By this, it is suggested that Zonguldak and east Moesian terranes behaved independently from the Istanbul–Balkan terranes during the closure of the Rheic Ocean. They very likely docked to Laurussia during Emsian by strike-slip faults and remained thereon at its platform margin, where the Middle–Late Devonian shallow-platform conditions were followed by fluvial (lagoon and delta) conditions and deposition of coal during Late Carboniferous.

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Section: Introductionmentioning

confidence: 99%

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

2012

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“…The main difference between the ZT and İT was explained by stratigraphic variations between the two and the presence of a Caledonian time thermal event in the ZT (Bozkaya et al, 2012). In the ZT, Paleozoic successions include a low-grade angular unconformity (Figures 1c and 2) between Wenlock graptolitic shales (Sachanski et al, 2010) and late Early Devonian (Emsian) (Göncüoğlu et al, 2004) carbonates, whereas in the İT, the deposition is continuous during the same time interval.…”

Section: Regional Geological Settingmentioning

confidence: 97%

Clay mineralogy, chemistry, and diagenesis of Late Devonian K-bentonite occurrences in northwestern Turkey

Türkmenoğlu¹,

Bozkaya²,

Göncüoğlu³

et al. 2015

Turkish J Earth Sci

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The products of explosive eruptions in the form of volcanic ash (tephra), after being transported for long distances by wind, are settled and altered to bentonites (smectite-rich volcanogenic clay rocks) in early diagenesis. In late diagenesis, these bentonites are transformed into K-bentonites by chemical modification and K-fixation with progressive illitization and then finally into metabentonites by low-grade metamorphism (Fortey et al., 1996). During diagenesis and very low-grade metamorphism, due to potassium enrichment, smectite transforms to mixed-layer illite-smectite (I-S) and then illite in K-bentonites (Weaver, 1953;Nadeau et al., 1985;Merriman and Roberts, 1990).The discovery of K-bentonites dates back as early as the 1920s. Since then, their geologic importance has been revealed and proven by ongoing interdisciplinary research. Nelson (1921Nelson ( , 1922 originally denoted the pyroclastic nature of some rocks in the Paleozoic rock system in the eastern part of the United States. Following Nelson's original remarks, Allen (1932), based on the crescent-shaped shard structures and the presence of sanidine, apatite, and euhedral zircon crystals, evidenced the volcanic origin of those deposits. Rosenkrans (1934) and Kay (1944aKay ( , 1944b were the first to use bentonites for stratigraphic correlations. The significance of K-bentonites as widespread marker beds has been recognized recently since they are also datable using fission track and U/Pb dating of zircons, K/Ar, and Ar/Ar of amphibole, biotite, and sanidine (Kolata et al., 1996).Worldwide research activities on K-bentonites have diversified aims such as discovering localities and studying their mineralogical, petrographic, and

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“…1c,d). The Upper Ordovician-Middle Silurian succession is represented by the Karadere, Ketencikdere and Fındıklı formations including graptolitic black and grey shales, with sandstones, siltstones (Schanski et al, 2010) and limestone interlayers (Dean et al, 1997) (Fig. 1d).…”

Section: Lo C At I O N a N D R E G I O N A L G E O Lo G I C A L S E Tmentioning

confidence: 99%

Geological features and geochemical characteristics of Late Devonian–Early Carboniferous K-bentonites from northwestern Turkey

et al. 2016

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Newly discovered K-bentonite beds, interstratified with limestones/dolomitic limestones of the Upper Devonian–Lower Carboniferous Yılanlı Formation, are exposed in the northwestern Black Sea region of Turkey, around Zonguldak and Bartın. K-bentonite samples collected from four different locations: the Gavurpınarı and Yılanlı Burnu quarries from the Bartın area, the Çimşir Çukurları quarry from the Şapça area, and the Güdüllü and Gökgöl highway tunnel section near Zonguldak city were investigated using optical microscopy, X-ray diffraction and inductively coupled plasma mass spectrometry in order to reveal their mineralogical and geochemical characteristics and understand their origin and evolution. The K-bentonites occur at different levels in the Yılanlı Formation as 2–40 cm-thick, greenish to yellowish beds cropping out several hundred metres along strike. Preliminary biostratigraphic data suggest that the protoliths of the Bartın (Gavurpınarı and Yılanlı Burnu) and Güdüllü K-bentonites were deposited at around the boundary between the Frasnian and Famennian, whereas those in the Şapça and Gökgöl sections are slightly younger (Devonian–Carboniferous boundary interval). The lithofacies types of the host carbonate rocks suggest an ‘epeiric’ shallow carbonate platform environment. Illite and mixed-layer illite-smectite were the major clay minerals in the K-bentonites. The K-bentonites from the Bartın area display a high degree of illitization and consist mainly of illite indicating high-grade diagenesis, whereas illite-smectite-rich samples from the Şapca and Gökgöl tunnel locations reflect relatively lower diagenetic conditions. According to their geochemical compositions, two groups of K-bentonites were distinguished, one with alkali basalt (Bartın area and Güdüllü locations) and one with trachyte affinities (Gökgöl tunnel and Şapça locations). Geochemical fingerprinting of K-bentonites by trace and rare earth element (REE) data suggest that tephras with alkali basalt composition have been derived by a source formed in a ‘continental back-arc’ setting, whereas the source of K-bentonites with trachytic precursors is related to ‘continental within-plate rifting’. An evaluation of the global Late Devonian and Devonian–Carboniferous volcanism suggests that the bentonite precursors may be related to late-Variscan magmatism in Laurussia.

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Late Telychian (early Silurian) graptolitic shales and the maximum Silurian highstand in the NW Anatolian Palaeozoic terranes

Cited by 18 publications

References 24 publications

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

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

Clay mineralogy, chemistry, and diagenesis of Late Devonian K-bentonite occurrences in northwestern Turkey

Geological features and geochemical characteristics of Late Devonian–Early Carboniferous K-bentonites from northwestern Turkey

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