Taxonomy and biostratigraphy of calpionellids and saccocoma across the jurassic-cretaceous boundary beds of the alci block: alacaatli olistostromes, Ankara, Turkey

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2019
Akgümüş, Begüm
The main aim of this study is to determine the exact position of the Jurassic- Cretaceous (the Tithonian-Berriasian) boundary based on the calpionellid species and their biozones within the pelagic limestone block (Alcı Block). To achieve this aim, the stratigraphic section-BA was measured as 59,30 meters throughout the Alcı Block and totally 72 samples were collected for the preparation of the thin sections. Totally 3 zones and 5 subzones have been designated as Chitinoidella Zone (boneti Subzone), Crassicollaria Zone (remanei and massutiniana subzones), Calpionella Zone (alpina and Remaniella subzones). Moreover, the “explosion” of Calpionella alpina at the base of the Berriasian was used as the criterion for the delineation of the boundary. However, the quantitative analysis (counting method) on calpionellids has been used for the first time in this study in order to obtain more accurate results and the measurements on calpionellids have been illustrated for the morphological comparison. All microfossil assemblages including microgranular and hyaline calpionellids, small benthic foraminifera and Saccocoma Agassiz have been identified by using their morphological/taxonomical features. Saccocoma Agassiz was studied at a species level for the first time in Turkey by this study. As a result, Saccocoma tenella Goldfuss and Saccocoma vernioryi Manni & Nicosia have been identified in detail. The pelagic limestone block of the Alacaatlı Olistostromes was defined as the basinal deposition based on the dominance of pelagic fossil assemblages, infrequent occurrence of the small benthic foraminifera and frequently observed distal calciturbidites throughout the section. Furthermore, the grey to white, thin to medium bedded limestone-marl alternations with calciturbiditic intercalations throughout the section indicates the Yosunlukbayırı Formation as the origin of this pelagic limestone block.
Citation Formats
B. Akgümüş, “Taxonomy and biostratigraphy of calpionellids and saccocoma across the jurassic-cretaceous boundary beds of the alci block: alacaatli olistostromes, Ankara, Turkey,” M.S. - Master of Science, Middle East Technical University, 2019.