Biostratigraphy, microfacies, sedimentary environments of the Gurpi and Amiran formations in the Gerdbisheh section, High Zagros
Abstract Biostratigraphy, microfacies and depositional environments of the Upper Cretaceous deposits (Gurpi and Amiran formations) were carried out in the Gerdbisheh section. The Gurpi Formation predominantly consists of shales interbedded with some argillaceous limestone layers. This formation disc...
| Main Authors: | , , |
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| Format: | Article in Journal/Newspaper |
| Language: | Persian |
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University of Isfahan
2023
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| Online Access: | https://doi.org/10.22108/jssr.2023.137414.1259 https://doaj.org/article/be9846e1e79f4e3ea6b7bbcb30b0f937 |
| Summary: | Abstract Biostratigraphy, microfacies and depositional environments of the Upper Cretaceous deposits (Gurpi and Amiran formations) were carried out in the Gerdbisheh section. The Gurpi Formation predominantly consists of shales interbedded with some argillaceous limestone layers. This formation disconformably overlies the Sarvak Formation and gradually underlies the Amiran Formation. The Amiran Formation is represented by grey to greenish shales, siltstones and sandstone intercalations which underlay the informal siliciclastic-carbonate unit 1. Planktonic foraminiferal assemblages have led to the recognition of six zones that reveal the late Coniacian?–early Maastrichtian age for the Gurpi Formation. Radiolaria and scattered planktonic foraminifera are the two main fossil groups present in the Amiran Formation. Therefore, based on the precence of the index planktonic foraminfera and the stratigraphic position the early-middle? Maastrichtian age is proposed for the Amiran Formation. We determined two microfacies in the interval of the Gurpi Formation and three petrofacies in the Amiran Formation. According to the obtained data the Gurpi Formation was deposited in the basinal setting, whereas the Amiran Formation is deposited as submarine fans on the slope part of a carbonate shelf under the control of turbidity currents. Keywords: Gurpi Formation, Amiran Formation, High Zagros, Foreland Basin, Late Cretaceous Introduction During the Cretaceous, the Neo-Tethys Oceanic crust started subducting under the Iranian Plate which was followed by foreland basin development (Alavi 1994, 2004; Piryaei et al. 2011). The late Coniacian through the late Maastrichtian (in some areas Paleocene) interval is represented by the Gurpi Formation which constitutes the main part of the newly created foreland basin (Ziegler 2001; Alavi, 2004; Piryaei et al. 2011; Orang et al. 2018). In the studied area the Cretaceous successions including Kazhdumi, Sarvak, Gurpi, Amiran and Tarbur formations are outcropped. The Gurpi Formation ... |
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