Middle and Upper Jurassic ammonites from the Dalichai Formation in north Semnan, Iran

Document Type: Original paper (Research paper)


1 Department of geology, faculty of science, University of Isfahan

2 Research Institute for Earth Sciences, Geological Survey of Iran, Tehran, Iran.

3 Department of Geology, Faculty of Science, Payam Noor University, Tehran, Iran.


The present reseach focuses on a collection of Bathonian-Oxfordian ammonite fauna from the Dalichai Formation in Mahdishar (northern Semnan, Iran), followed by the description of the sedimentary succession of Kuh-e-Rahband area. In the studied section, the Dalichai Formation is characterized by 122 m of thick marls and grey medium to thick-bedded limestones and argillaceous limestones with chert nodules, deposited in a deep basinal setting. Four lithostratigraphic units are distinguished in this paper. The studied ammonite fauna consists of 40 specimens attributed to the families, Phylloceratidae, Perisphinctidae, Oppeliidae and Aspidoceratidae: Palaeobiogeographically the fauna shows close relationships with Western Europe and the Sub-Mediterranean regions.


Volume 1, Issue 1
Winter and Spring 2019
Pages 25-48
  • Receive Date: 28 June 2019
  • Revise Date: 15 July 2019
  • Accept Date: 22 August 2019