Coniacian/Santonian calcareous nannofossil and planktonic foraminifera in the Kurdistan Region, NE Iraq: biostratigraphy
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ORIGINAL PAPER
Coniacian/Santonian calcareous nannofossil and planktonic foraminifera in the Kurdistan Region, NE Iraq: biostratigraphy and bioevents Rawand Bakir Noori Jaff 1 & Khaled Al-Kahtany 2 Received: 2 July 2020 / Accepted: 2 September 2020 # Saudi Society for Geosciences 2020
Abstract Calcareous nannofossil and planktonic foraminiferal biostratigraphy and bioevents in the Zewe section situated in the Kurdistan Region, NE Iraq, have been described in detail. High-resolution standardization of Coniacian/Santonian calcareous nannofossil and planktonic foraminiferal biostratigraphic datums categorized the reviewed succession into two nannofossil (CC15 and CC16) zones which are utterly equivalent to two planktonic foraminiferal (Dicarinella concavata and D. asymetrica) zones. The Coniacian/Santonian stage boundary was fixed based on the FOs of the premium reliable calcareous nannofossil and planktonic foraminiferal assemblages. The successive bioevents, in stratigraphic order, characterizing the Coniacian/Santonian stage boundary in the conspicuous inspected section are as follows: the FOs of Lithastrinus grillii (Upper Coniacian); Lucianorhabdus cayeuxii (Uppermost Coniacian); and Micula concava (Lowermost Santonian). Other nannofossil assemblages in Zone CC16 are the FOs of Radiolithus planus, Quadrum giganteum, and Eprolithus floralis. The planktonic foraminiferal bioevents are as follows: the FO of Dicarinella asymetrica (Upper Coniacian), followed upward by the FO of very rare Sigali carpatica (Uppermost Coniacian) and common Globotruncana linneiana at the base of the Santonian stage. Keywords Planktonic foraminifera . Calcareous nannofossils . Coniacian/Santonian boundary . Kurdistan Region . Iraq
Introduction Microfossil biostratigraphical examinations of different regions show substantial inconsistency in the bioevents used to describe the Coniacian/Santonian stage boundary. Thus, a number of dissimilar Late Cretaceous calcareous nannofossil and planktonic foraminiferal zonal frameworks have been proposed over the past fifty years. Several of these biozonations were developed using low-latitude Tethyan Regions, which are commonly described by the highest Responsible Editor: Beatriz Badenas * Khaled Al-Kahtany [email protected] Rawand Bakir Noori Jaff [email protected] 1
College of Education and Languages, Department of General Sciences, Charmo University, Chamchamal, Kurdistan Region, Iraq
2
Seismic Studies Center, College of Science, King Saud University, Riyadh, Saudi Arabia
diversity of species (e.g., Roth 1973; Sissingh 1977; Caron 1985; Robaszynski and Caron 1995; Robaszynski et al. 2000; Sari 2006; Farouk and Faris 2012; Elamri et al. 2014; Farouk 2014; Farouk et al. 2016; Jaff et al. 2015; Farouk et al. 2017; Petrizzo et al. 2019; Faris et al. 2019; Fang et al. 2020). The pelagic and argillaceous limestones of the Kometan Formation, which yield rich in well-preserved microfossils, were deposited in a relatively narrow seaway occupying the range of Low and High Folded Zon
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