Palynology of the Middle Jurassic strata from the Alborz Ranges, northwestern Iran
Palinología de estratos del Jurásico Medio de las Montañas Alborz, Noroeste de Irán
Freshteh Sajjadi Hezaveh1, Firoozeh Hashemi Yazdi2,*, Ali Khazaei1, Navid NavidiIzad3, Mohammad Taghi Badihagh4
1 School of Geology, College of Science, University of Tehran, Tehran, Iran.
2 Department of Palaeobotany, Research Institute of Forests and Rangelands, Agricultural Research, Education and Extension Organization (AREEO), Tehran, Iran.
3 Department of Geology, Faculty of Earth Sciences, Kharazmi University, Tehran, Iran.
4 University of Chinese Academy of Sciences, Beijing 100049, China
Corresponding author: (F. Hashemi Yazdi) This email address is being protected from spambots. You need JavaScript enabled to view it.
How to cite this article:
Sajjadi Hezaveh, F., Hashemi Yazdi, F., Khazaei, A., Navidi-Izad, N., Taghi Badihagh, M., 2025, Palynology of the Middle Jurassic strata from the Alborz Ranges, northwestern Iran: Boletín de la Sociedad Geológica Mexicana, 77(1), A141124. http://dx.doi.org/10.18268/BSGM2025v77n1a141124
Manuscript received: July 21, 2024; Corrected manuscript received: November 1, 2024; Manuscript accepted: November 13, 2024
ABSTRACT
Palynomorphs are used for palynostratigraphy, and to derive paleoecological and paleobiogeographical inferences from the Middle Jurassic Shemshak Formation, Alborz Ranges, northwestern Iran. The rock unit contains diverse, reasonably preserved palynofloras dominated by miospores and dinoflagellate cysts. Vertical distribution of miospores allows for the introduction of Klukisporites variegatus -Striatella spp.Contignisporites burgeri assemblage zone in the host strata. The presence of such key miospore species as Striatella jurassica, S. patenii, S. seebergensis, and Contignisporites burgeri indicates a Middle Jurassic (late Bajocian–Bathonian) age. Based on the stratigraphic distribution of dinoflagellate cysts, encountered Cribroperidinium crispum Total Range Biozone (late Bajocian); Dichadogonyaulax sellwoodii Interval Biozone (Bathonian–early Callovian), and Subzone “a” of the D. sellwoodii Zone (early–middle Bathonian) are identified. Miospores dominating the examined assemblages are assigned, in ascending order of abundance, to Pterophyta, Coniferophyta, Pteridospermophyta, Lycophyta, Ginkgophyta, Cycadophyta, and Sphenophyta. Such parental vegetation apparently flourished under a wet, warm-to-warm-temperate climate. The co-occurrence of such index warm-moderate water dinoflagellate cysts as Pareodinia halosa, Ctenidodinium continuum, and Pareodinia ceratophora supports this overview. The assemblages though contain both Eurasian and Gondwanan elements but bear closer similarity to those from the former, thus suggesting paleoproximity to the northeastern margin of the Neotethys Ocean during the Middle Jurassic.
Keywords: Miospores, Dinoflagellate cysts, Paleobiogeography, Paleoecology, Shemshak Formation, Iran.