Geologia Croatica, Vol. 79 No. 3, 2026.
Original scientific paper
Remarks on the Carboniferous blocks in the Late Cretaceous Elmadağ Olistostrome from the Intra-Pontide Ocean: Biochronology of Foraminiferal assemblages from the Ankara region, central Türkiye
Melikan Akbaş
; Department of Geological Engineering,Konya Technical University, Konya, Türkiye
Cengiz Okuyucu
; School of Land Registry and Cadastre, Hacı Bayram Veli University, Ankara, Türkiye
*
Kağan Tekin
; Department of Geological Engineering, Hacettepe University, Beytepe, Ankara, Türkiye
Alaettin Tuncer
; Department of Geological Engineering, Hacettepe University, Beytepe, Ankara, Türkiye
Kaan Sayit
; Department of Geological Engineering, Middle East Technical University, Ankara, Türkiye;
* Corresponding author.
Abstract
A detailed biostratigraphic study of the Carboniferous blocks within the Late Cretaceous Elmadağ Olistostrome exposed around Ankara city was conducted on two stratigraphic sections (Kapaklı and Sapankıran) and two isolated samples. While the Kapaklı section and two isolated samples are composed uniformly of platform limestones, the Sapankıran section is characterized dominantly by sandstones with platform limestone interlayers. Based on Foraminiferal assemblages, the isolated sample 21-El-41 provides the oldest age (middle Viséan), whereas isolated sample 21-EL-06 yields the early Serpukhovian age. Three local foraminiferal biozones are defined in the Serpukhovian Kapaklı section: the Neoarchaediscus postrugosus - Biseriella parva Assemblage Zone, the Eostaffellina decurta Zone and Eostaffellina paraprotvae Zone. The date recovered in this study from the smaller foraminifers and fusulinids implies that the youngest age (late Early-late Bashkirian) within the Carboniferous blocks is from the Sapankıran section. According to the correlation with nappes (e.g., Hadim Nappe, Bolkar Dağ Nappe, and Beyşehir-Hoyran nappes) originating from the Izmir-Ankara-Erzincan Ocean (southern branch of Northern Neotethys), the upper Lower-upper Bashkirian strata are characterized by similar lithology and a common foraminiferal assemblage in both from Intra-Pontide and Izmir-Ankara-Erzincan (Hadim Nappe) units. The Serpukhovian strata examined in this study are composed of carbonates without any siliciclastic input, while this interval corresponds to siliciclastic-dominated rock units in the Hadim Nappe. Additionally, the Middle–Upper Pennsylvanian deposits within the Carboniferous blocks of Intra-Pontide sequences could not be detected in this study, as it has been observed in the Bolkar Dağı and Beyşehir-Hoyran nappes.
Keywords
Foraminifera; Carboniferous; Elmadağ Olistostrome; Intra-Pontide Ocean; Neotethys
Hrčak ID:
352769
URI
Publication date:
27.10.2026.
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