Introduction of Ammonites from the Dalichai Formation in Polour Section Central Alborz, Iran
DOI:
https://doi.org/10.52562/injoes.2025.1341Keywords:
Ammonites, Dalichai Formation, Central Alborz, South PolourAbstract
The studies done on Dalichai Formation in Central Alborz, South Polour Formation of an 80 m thick that are systematically sampled at intervals of 2 meters and selected the 40 rock samples for the preparation of thin sections considered and in addition to lithology; characteristics of the stone, and index examples of Ammonites were also studied. Dalichai formation lithology in the study area is rich in terms of alternating gray sandstone and marl with Ammonites Fauna. Based on the study of fossil fauna, the oldest identified ammonite in the studied section is Procerites (Early Bathonian), and the youngest is Reineckeia sp. (Late Callovian). The distribution of ammonites indicates that the eastern Alborz region had marine connections with northwestern Europe and the Mediterranean marginal areas during the Middle Jurassic period, and the study area was located north of the Tethys Ocean. Based on its stratigraphic position of the middle Jurassic Age Formation, Dalichai Ammonites with peer review study sections and microfossils Bathonian-Callovian age Dalichai is accurate. Lar Formation covers this formation with a gradual contact and has been parallel to the Shemshak Formation on an erosional unconformity. Through the examination of stratigraphy and the correlation of formations in the studied sequence, it was determined that the lower part of the Dalichai Formation is equivalent to other formations in Iran, including the Parvdeh Formation in the Shotori Mountains, the Kashfrood Formation in the Kopeh Dagh, and the lower part of the Baghamshah Formation in the Tabas Basin. The variations in thickness of the Dalichai Formation in the eastern Alborz region indicate relative subsidence of the sedimentary basin, a delay in sea-level rise, and the exit of sediments from seawater. These changes are indicative of the Middle Cimmerian tectonic event, which is observed as an erosional unconformity at the lower boundary of the Dalichai Formation.
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References
Aghanabati, A. (2015). Geology of Iran. Geological survey and mineral exploration of Iran.
Alavi-Naini, M. (1972). Etude geologique de la region de Djam (Report No. 2). Geological survey of Iran.
Annells, R. N. (1975). Explanatory text of the Qazvin and Rasht quadrangles map. Geological survey of Iran, Tehran.
Dehbozorgi, A., Hashemi Yazdi, F., & Sajjadi Hazaveh, F. (1976). Palynostratigraphy and paleo- sedimentary environment of Dalichai Formation in Poldokhtar stratigraphic section. Journal of Applied Sedimentology, 6(11), 35-48.
Dietze, V., Seyed-Emami, K., & Raoufian, A. (2014). Morphoceras Douvillé, 1880 and Ebrayiceras Buckman, 1920 from the Dalichai Formation (Lower Bathonian) North and Northeast of Damghan (Northeast Alborz, Iran). Zitteliana, 54, 15-22.
Ezoji, H., Majidifard, M.R., Maleki, Z., & Vaziri, S. H. (2023). Biostratigraphy of Dalichai Formation in Bar and Sarmeran sections (Binalud Mountains) Northeastern of Iran based on ammonite fauna with special emphasis on Phylloceratidae Family. Geopersia, 13(1), 209-227. https://doi.org/10.22059/geope.2023.351966.648691
Farahani, T. S., Majidifard, M. R., & Kebreaee-Zadeh, M. R. (2019). Middle and Upper Jurassic Ammonites from the Dalichai Formation (North Semnan, Iran). Iranian Journal of Geoscience Museum, 1(1), 25-48.
Farahani, T. S., Majidifard, M. R., Kebreaee-Zadeh, M. R., & Mohamadi, M. (2015). Study of the lithostatigraphy and biostratigraphy of ammonite fauna of the Dalichai Formation at the Mahdishar section, N Semnan. Quarterly Journal of Geosciences, 24(94), 27-39. https://doi.org/10.22071/gsj.2015.42563
Fürsich, F. T., Wilmsen, M., Seyed-Emami, K., Cecca F., & Majidifard, M. R. (2005). The upper Shemshak Formation (Toarcian - Aalenian) of the Eastern Alborz (Iran): Biota and palaeoenvironments during a transgressiv-regressive cycle. Facies, 51, 379-398. https://doi.org/10.1007/s10347-005-0051-z
Hashemi Yazdi, F. (2015). Palynology and palaeoecology of the Dalichai Formation in central-eastern Alborz Basin and the Hojedk Formation at the east-central Iran (Doctoral dissertation, Faculty of Geology, College of Science, University of Tehran, 388 p. In Persian).
James, G. A., & Wynd, J. G. (1965). Stratigraphic nomenclature of Iranian oil consortium, agreement area. American Association of Petroleum. AAPG Bulletin, 49(12), 2182–2245. https://doi.org/10.1306/A663388A-16C0-11D7-8645000102C1865D
Makvandi, R. (1960). The study of stratigraphy and paleontology of Dalichai and Lar formations in Mount Sharaf Semnan, Eastern Alborz (Masters dissertation, Azad University, North Tehran branch).
Mohammadi Monfared, M. (1957). Stratigraphy and Ammonite Fauna of Dalichai and Lar formations in Mount Sharaf Semnan, Eastern Alborz (Masters dissertation, University of Isfahan).
Moore, R. C. (1957). Treatise on Invertebrate Paleontology- Part L. Geological Society of America and University of Kansas Press, Kansas.
Niknahad, M. (1948). The study of stratigraphy and paleontology of Dalichai formations in the southeast of Maraqa (Western Alborz) according to Ammonite Fauna (M.Sc. dissertation, Geological Survey and mineral exploration of Iran).
Rafiei, A. (2013). Miospores of Jurassic sediments, northwest of Semnan, Central Alborz (M.Sc. dissertation, University of Tehran).
Raoufian, A., Zand Moghaddam, H., & Seyed–Emami, K. (2019). Depositional history of Middle-Upper Jurassic succession at the Binalud Mountains, NE Iran: implications of ammonite, trace fossil and stable isotopes in palaeoenvironmental analysis. Historical Biology, 32(2), 1-18. https://doi.org/10.1080/08912963.2018.1563078
Seyed-Emami, K., & Raoufian, A. (2017). Ammonites from Bathonian and Callovian (Middle Jurassic) North of Damghan, Eastern Alborz, North Iran. Zitteliana, 89, 253-270.
Seyed-Emami, K., Schairer, G., Raoufian, A., & Shafeizad, M. (2013). Middle and Late Jurassic ammonites from the Dalichai Formation west of Shahrud (East Alborz, North Iran). Neues Jahrbuch für Geologie und Paläontologie, 267(1), 43-66. https://doi.org/10.1127/0077-7749/2012/0296
Seyed-Emami, K., Raoufian, A., & Mönnig, E. (2015). Macrocephalitinae (Ammonoidea, Middle Jurassic) from North and Central Iran. Neues Jahrbuch für Geologie und Palontologie, 278(3), 257-279. https://doi.org/10.1127/njgpa/2015/0527
Shafizad, M. (1961). The study of stratigraphy and paleontology of Dalichai Formation in Eastern Alborz, west of Shahroud (M.Sc. Thesis, Islamic Azad University, North Tehran branch).
Steiger, R. (1966). Die Geologie der West-Firuzkuh-Area, Zentralelburz/Iran (Doctoral dissertation, University of Zurich).
Stocklin, J., & Setudehnia, A. (1991). Stratigraphic Lexicon of Iran, Central, North and East Iran (Report No. 18). Geological Survey of Iran.
Totonchi, B. (1961). Stratigraphic and paleontological study of Dalichai Formation in the south of Polour area, southeast of Poldokhtar (Masters dissertation, Islamic Azad University, North Tehran branch).
Wilmsen, M., Fürsich, F.T. & Taheri, J. (2009). The Shemshak group (Lower-Middle Jurassic) of the Binalud mountains, NE Iran: stratigraphy, depositional environments and geodynamic implications. In Geological Society London, Special Publications (Vol. 312), 175-188. https://doi.org/10.1144/SP312.8
Zadesmaeil, M., Majidifard, M. R., Vaziri, S. H. & Jahani, D. (2021). Lithostratigraphy and Biostratigraphy of the Dalichai Formation in Absharaf Section, Northwest of Damghan on the base of Ammonites (East Alborz), Scientific Quaterly Journal. Geosciences, 31(2), 91-100. https://doi.org/10.22071/GSJ.2017.97439.1250
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