Zoophycos ichnogenus distribution and paleoenvironmental analysis: examples from the Mississippian Mobarak formation (Alborz Basin, Iran)

ABSTRACT

Zoophycos

is a characteristic trace fossil in the Mississippian in the Alborz Basin deposits of north Iran, and is described for the first time in the Mobarak Formation. The vertical distribution of the carbonate deposits bearing Zoophycos provided the basis for distinguishing three distinct types of sedimentary sequences including Zoophycos (type A, B, and C) in shallow marine sediments of Mobarak Formation. Type A is composed of rare to common density of small to medium lobed Zoophycos. Type B is characterized by common density of medium lobed Zoophycos. This ichnogenus in type A and B is associated with Palaeophycus. The low diversity and bioturbation of the trace fossils would be the result of a stressful environment characterized by optimal water circulation and high-energy conditions. Type C consists of abundant density of large lobed Zoophycos. Type C is associated with Chondrites and planolites. The high diversity and bioturbation of the trace fossils in type C than type A and B would be the result of a calm environment characterized low-energy conditions. Under low sedimentation rate, stable paleoenvironment, dysaerobic conditions, and high amount of benthic food, the size of Zoophycos is the biggest, whereas in the high sedimentation rate, unstable paleoenvironment, aerobic conditions, and shortage of benthic food, the size of Zoophycos is small.

KEYWORDS:

• Alborz Basin
• carbonate ramps
• Iran
• Mississippian
• storm deposits
• Zoophycos

Acknowledgments

We acknowledge the Department of Geology, Faculty of Science, Ferdowsi University of Mashhad, Iran for financial support and field expenses through grant No. 3/43573. We would like to extend my thanks to Mr. Mehdi Hadi for his help during the field works. We are also grateful to Mr. Aram Bayet-Goll for carefully reading the manuscript, his guiding comments, and constructive suggestions that improved the quality of this paper.

Disclosure statement

No potential conflict of interest was reported by the authors.