Location of the western Pontides, NW Turkey, during Triassic time: preliminary palaeomagnetic results

Sanbudak, Mustafa; Sanver, M.; Ponat, Ertuğrul

doi:10.1111/j.1365-246x.1989.tb05249.x

Cited by 20 publications

(8 citation statements)

References 9 publications

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“…7). Palaeomagnetic data from Ordovician and younger rocks of the Istanbul zone are compatible with a palaeo-latitude close to the southern margin of Laurasia (Saribudak et al 1989;Evans et al 1991). …”

Section: Discussionmentioning

confidence: 68%

Geochronology of the Karadere basement (NW Turkey) and implications for the geological evolution of the Istanbul zone

Chen

Siebel

Satır

et al. 2001

Int J Earth Sci (Geol Rundsch)

268

102

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Earlier geological work in the Istanbul zone, western Pontide tectonic belt, has revealed the presence of extensive basement outcrops exposed underneath Palaeozoic and Mesozoic to Tertiary cover sequences. The basement of suspected Neoproterozoic age plays an important role in understanding the crustal accretion process in NW Turkey. We report the first results of a detailed Pb-Pb and U-Pb zircon study complemented by Nd-Sr whole rock and mineral data from basement rocks exposed in the Karadere valley, Safranbolu area. Five samples were selected for this study, comprising three metagranitoids and two metasediments. Zircon geochronology indicates that the metagranitoids were formed during Late Proterozoic pan-African magmatic events between 590 and 560 Ma. The rocks are of tonalitic and granitic composition and have low Nb/Y ratios and Ti contents, consistent with those of arc rocks. A continental arc setting is supported by their Sr and Nd isotope data that indicate a contribution of a mantle source as well as crustal assimilation during magma genesis. The metasediments can clearly be distinguished from the metagranitoids by their higher 87 Sr/ 86 Sr ratios and lower ε Nd -values at 580 Ma, which supports the suggestion that the arc was underlain by mature continental crust. Zircons from the metasediments yield a range of Pb-Pb ages between 1,860 and 710 Ma. Thirty per cent of them fall between 890 and 710 Ma, possibly suggesting a derivation from Gondwana (Afro-Arabian) regions. A Sm-Nd garnetwhole rock analysis obtained on a metagranite gives an age of 559±8 Ma, which either reflects pre-metamorphic magmatic growth of garnet in a felsic melt or a syntectonic high-temperature metamorphic event. Uplift and cooling of the basement is further constrained by Rb-Sr biotite ages of 548-545 Ma. These lower Cambrian mineral ages demonstrate that the Istanbul zone was not thermally reactivated during the Hercynian, Cimmerian or Alpine orogeny, in contrast to its neighbouring tectonic zones, confirming its role as a suspect terrane in the modern western Pontide tectonic belt.

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Section: Discussionmentioning

confidence: 68%

Geochronology of the Karadere basement (NW Turkey) and implications for the geological evolution of the Istanbul zone

Chen

Siebel

Satır

et al. 2001

Int J Earth Sci (Geol Rundsch)

268

102

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“…Donetz basin; Kerey 1984). Palaeomagnetic data from the Scythian alkaline lavas in the Kocaeli Peninsula (see earlier) also imply Eurasian pole positions for the Istanbul Fragment (Saribudak et al 1989).…”

Section: D Caucasusmentioning

confidence: 93%

A Late Palaeozoic‐Early Mesozoic marginal basin along the actives sourthern continental margin of Eurasia: Evidence from the central Pontides (Turkey) and adjacent regions

Ustaömer

Robertson

1993

Geological Journal

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Remnants of two ‘Palaeotethyan’ oceanic basins are exposed in the Central Pontides of northern Turkey, separated by a continental sliver and an oceanic arc. The southern basin corresponds to the main Tethys (‘Palaeotethys’), which partially closed in Early Mesozoic time following northward subduction under the southern, active continental margin of Eurasia. The northern basin (Küre Complex) opened above the ‘Palaeotethyan’ subduction zone as a marginal basin, following rifting of a continental fragment (Istanbul fragment) from Eurasia. Marginal basin opening apparently dates from the Late Palaeozoic in the east (Küre basin) and from the Triassic in the west (Kocaeli basin). Basin closure was achieved by southward subduction‐accretion, in pre‐Late Jurassic times, leaving ‘Neotethys’ open to the south. Counterparts of the Küre Complex are found in the adjacent Crimea (Taurian Series), Istranca (Zabernevo Complex), Dobrogea (Nalbant flysch) and Caucasus (pre‐Late Jurassic Southern Slope Basin) regions. Basin opening was accompanied by oceanic crust genesis, at least in the Pontides and Caucasus. Closure before Mid‐Jurassic time was achieved by subduction‐accretion processes, whereby oceanic crust and deep‐sea sediments (including sulphides) were detached and structurally assembled, while oceanic basement was subducted. Marginal basin opening and closure is seen as one in a series of events along a long‐lived, active south Eurasian continental margin.

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“…For this reason, the Bilecik limestone was excluded from consideration with the Pontides. It was stated in Sanbudak, Sanver & Ponat (1989) that the western Pontides were part of the southern margin of Eurasia during Triassic time ( I = 5 0°) . This apparent contradiction with Jurassic-Cretaceous palaeomagnetic inclination data (I = <30") was explained in terms of the western Pontides having taken an excursion to the south between Triassic and Jurassic time (Saribudak 1989).…”

Section: Discussionmentioning

confidence: 98%

“…For this reason, the Bilecik limestone was excluded from consideration with the Pontides. It was stated in Sanbudak, Sanver & Ponat (1989) terms of the western Pontides having taken an excursion to the south between Triassic and Jurassic time (Saribudak 1989). Palaeomagnetism of Jurassic sediments from that part of Bulgaria lying at the southern border of the Moesian platform indicates that the region belonged to stable Europe and its paiaeolatitude was approximately 39" (Kruczyk et al 1988).…”

Section: Discussionmentioning

confidence: 99%

A palaeomagnetic approach to the origin of the Black Sea

Sarıbudak¹

1989

Geophysical Journal International

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SUMMARY Available palaeomagnetic data for the circum‐Black Sea region are reviewed with the object of evaluating the geodynamical evolution of the Black Sea. Jurassic data from the south of the Stara planina‐Forebalkan zone (south of the Moesian platform) in Bulgaria, which was then part of the east European platform, place the region at about 39° latitude; while the Pontides, the northernmost tectonic unit of Turkey, were at a lower latitude (10‐15°). Palaeomagnetic investigations on Upper Cretaceous magmatic rocks sampled in different part of the Srednogorie tectonic unit (southern boundary of the Stara planina‐Forebalkan) indicate that the region was at 39° palaeolatitude during the Upper Cretaceous, while the Pontides had moved northward to 23° palaeolatitude since Early Cretaceous time. The Great Caucasus domain of the USSR was welded to Eurasia by Coniacian time and had a palaeolatitude of 36°. Calculated palaeopole positions for the above‐mentioned geological times for the Pontides fit well with the African palaepoles but largely deviate from the Eurasian ones. Taken together, these observations indicate that the Pontides were not part of Eurasia; instead, they were separated from the east European platform by the early Mesozoic Tethys. This conclusion does not favour the rifted ‘back‐arc’ hypothesis for the formation of the Black Sea during Cretaceous time, as suggested by some researchers (Adamia et al. 1977, Hsüet al. 1977, Sengör & Yilmaz 1981).

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Location of the western Pontides, NW Turkey, during Triassic time: preliminary palaeomagnetic results

Cited by 20 publications

References 9 publications

Geochronology of the Karadere basement (NW Turkey) and implications for the geological evolution of the Istanbul zone

Geochronology of the Karadere basement (NW Turkey) and implications for the geological evolution of the Istanbul zone

A Late Palaeozoic‐Early Mesozoic marginal basin along the actives sourthern continental margin of Eurasia: Evidence from the central Pontides (Turkey) and adjacent regions

A palaeomagnetic approach to the origin of the Black Sea

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