Reassessment of the age and depositional environments of the Eocene Çayraz Formation, a reference unit for Tethyan larger benthic foraminifera (Haymana Basin, central Turkey)

Ercan Özcan*, Aynur Hakyemez, Attila Çiner, Aral I. Okay, Mohamed Soussi, Kamel Boukhalfa, Ali Osman Yücel

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

8 Citations (Scopus)

Abstract

The Çayraz Formation, a reference unit for Tethyan Ypresian-middle/late Lutetian larger benthic foraminifera (Haymana Basin, central Turkey), is a thick (>350 m) ‘shallow-marine’ mixed carbonate-siliciclastic sequence, divided into lower, middle and upper units. The lower and upper units predominantly consist of rhythmic intercalations of limestone and marly/silty beds with abundant larger benthic foraminifera (LBF), and the middle unit is composed of massive fine siliciclastic sediments, mostly barren in LBF and macrofossils. By studying three sections (ÇAYA, ÇAYB, and YEŞ), encompassing the lower unit, we show that the Çayraz Formation (ca. 100 m-thick) displays notable vertical and lateral variability in benthic fauna and facies along an SE-NW transect at its type locality near Çayraz village. The distribution of LBF and facies patterns indicate a general shallowing upward trend, with more open marine environments in the easterly section (ÇAYA) and restricted shallow marine to continental environments with low diversity fauna in the westerly section (YEŞ). A depositional setting ranging from outer to inner-ramp with continental influence only in the westerly section is proposed. Key orthophragminid and alveolinid taxa from the lower unit of the Çayraz Formation indicate shallow benthic zones (SBZ) 9/10 for its lower part, and SBZ 12 for its upper part, suggesting a late Ypresian age. The massive marly/silty section of the middle unit of the Çayraz Formation overlies the Alveolina-bearing limestones in all sections and yielded abundant planktonic foraminifera suggestive of P9 Zone. This implies a sharp environmental transition from platform to basin across the Ypresian-Lutetian boundary.

Original languageEnglish
Article number104304
JournalJournal of Asian Earth Sciences
Volume193
DOIs
Publication statusPublished - 15 May 2020

Bibliographical note

Publisher Copyright:
© 2020 Elsevier Ltd

Funding

This work was realized within the scientific collaboration project between TÜBİTAK (Turkey) and MHESR (Tunisia) (Project no: 114Y401). We thank Dr. Ercümet Sirel and an anonymous reviewer for their constructive comments that greatly improved the quality of the paper.

FundersFunder number
Türkiye Bilimsel ve Teknolojik Araştirma Kurumu
Ministry of Higher Education and Scientific Research114Y401

    Keywords

    • Eocene
    • Facies
    • Haymana Basin
    • Larger benthic foraminifera
    • Planktonic foraminifera
    • Turkey
    • Çayraz Formation

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