Paleo-exhumation histories of the Sakarya and the Istanbul Zones of the Western Pontides, the Almacık Block and its surroundings, NW Turkey

Gürsel Sunal*, Ali Akın, M. Korhan Erturaç, Cemre Ay, István Dunkl

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Özet

The Almacık Block is a tectonic sliver formed during the activity of the North Anatolian Fault Zone (NAFZ). It includes two important tectonic zones of the Western Pontides (NW Anatolia): the İstanbul and the Sakarya Zones meet along a suture zone called the Intra-Pontide Suture Zone (IPSZ). The units within the İstanbul Zone are exposed in the eastern part of the Almacık Block, whereas the rocks of the Sakarya Zone are exposed in the west. In the presented study, some of the magmatic rocks have been analysed using the zircon U-Pb method: these rocks have previously been either incorrectly or not dated. The U-Pb results have shown that some of the granitic rocks in the İstanbul Zone, which intruded into the amphibolites of the Intra-Pontide Suture Zone, have a crystallization age of 559–556 Ma. A granitoid block in the Upper Cretaceous wild flysch formed over the units of the İstanbul Zone had an age of ~566 Ma. Two distinct granitoid bodies in the Sakarya Zone were dated at 404.5 ± 3.9 Ma (Early Devonian) and 161.8 ± 0.82 Ma (Late Jurassic) ages. The palaeo-exhumation evolutions of the zones were obtained using the zircon (U-Th)/He technique (ZrHe) to understand the differences in the geological evolution of the individual zones. ZrHe ages of the samples obtained from the İstanbul Zone indicate a pronounced Early Cretaceous palaeo-exhumation period. The Middle-Upper Jurassic Mudurnu Formation in the Sakarya Zone gave ZrHe ages close to its sedimentation age, which indicates that the major part of the unit was not buried too deep to open the ZrHe closure system. Unlike those the İstanbul Zone, the main ZrHe age peaks of the Sakarya Zone are ~202, 160, 98, 74, and 52 Ma. Finally, a sample of the metamorphic rocks that were assigned to the IPSZ yielded a peak age of ~63 Ma, which indicates that the final closure of the Intra-Pontide Ocean (IPO) took place during the Early Tertiary.

Orijinal dilİngilizce
Sayfa (başlangıç-bitiş)1267-1288
Sayfa sayısı22
DergiInternational Geology Review
Hacim65
Basın numarası8
DOI'lar
Yayın durumuYayınlandı - 2023

Bibliyografik not

Publisher Copyright:
© 2022 Informa UK Limited, trading as Taylor & Francis Group.

Finansman

This study was supported by TÜBITAK (The Scientific and Technical Research Council of Turkey, Project no: CAYDAG 109Y257) and the İstanbul Technical University (BAP Project No. MGA-2018- 41082). We are so grateful to Fatma Gülmez for sharing the knowledge obtained during her master’s degree study in the region (Gülmez ). The authors thank Dr. Cavazza and anonymous reviewer for their thoughtful reviews and constructive criticism of the manuscript. We are thankful to Dr. Stern for editorial handling.

FinansörlerFinansör numarası
Türkiye Bilimsel ve Teknolojik Araştırma KurumuCAYDAG 109Y257
Istanbul Teknik Üniversitesi
Bilimsel Araştırma Projeleri Birimi, İstanbul Teknik ÜniversitesiMGA-2018- 41082

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