Investigation of sub-ichnofacies of the Nerites ichnofacies in the upper part of the Late Cretaceous flysch deposits in the Jolfa region, northwestern Iran, Alborz Basin

Taghdisi Nikbakht, Samira; Badpa, Mahdi; Salahi, Mir Amir; Nasiri, Yaghub

doi:10.22071/gsj.2026.559536.2234

Investigation of sub-ichnofacies of the Nerites ichnofacies in the upper part of the Late Cretaceous flysch deposits in the Jolfa region, northwestern Iran, Alborz Basin

Articles in Press

Document Type : Original Research Paper

Authors

Samira Taghdisi Nikbakht ¹

Mahdi Badpa ²

Mir Amir Salahi ³

Yaghub Nasiri ¹

¹ Assist. Prof., Department of Geology, Faculty of Sciences, University of Gonabad, Gonabad, Iran

² Assist. Prof. Department of Geology, Faculty of Sciences, Ferdowsi University of Mashhad, Mashhad, Iran

³ Department of Biology, Faculty of Basic Science, University of Maragheh, P.O. Box 55136-553, Maragheh, Iran.

10.22071/gsj.2026.559536.2234

Abstract

A detailed study aimed at investigating the abundance of Late Cretaceous ichnofaunal assemblages in the Jolfa area,
East Azerbaijan Province, indicates that these assemblages are reliable tools for interpreting the depositional
environment of submarine fans. The types of trace fossils and their stratigraphic arrangement are related to favorable
biotic zones; therefore, they are employed to infer information concerning the differentiation of sub-environments
within the turbidite fan system, sedimentation rate, and substrate consistency. The proximal and axial parts of the
sandy system in the studied section contain assemblages characterized by low diversity and low bioturbation intensity,
which are mostly dominated by post-depositional trace fossil suites. However, the distal parts show an increase in both
diversity and bioturbation intensity, displaying pre-depositional trace fossil assemblages. The identified ichnofossil
assemblages in the studied section correspond to the Nereites ichnofacies. Five sub-ichnofacies of the Nereites
ichnofacies were recognized in the studied deposits, which may indicate a trend toward increasing water depth. These
include: (0) Ophiomorpha rudis sub-ichnofacies, (8) mixed Ophiomorpha rudis–Paleodictyon sub-ichnofacies, (3)
Paleodictyon sub-ichnofacies, (2) mixed Nereites–Paleodictyon sub-ichnofacies, and (1) Nereites sub-ichnofacies.

Keywords

Trace fossil

Ichnofacies

Nereites

Turbidite

Subjects