Ichnotaxonomic analysis and depositional controls on the carbonate ramp ichnological characteristics of the Deh-Sufiyan Formation (Middle Cambrian), Central Alborz, Iran

Abstract

The trace fossil assemblages from the Unit 2 of Deh-Sufiyan Formation are described for the first time from The Central Alborz Range of northern Iran,  improving the record of the assemblages in the Cambrian of the Middle East. Twenty-one ichnogenera have been identified in the Deh-Sufiyan Formation, namely Arenicolites, Bergaueria, Chondrites, Circulichnus, Cruziana, Diplichnites, Didymaulichnus, Diplocraterion, Halopoa, Helminthopsis, Gordia, Gyrophyllites, Lockeia, Monomorphichnus, Palaeophycus, Phycosiphon, Planolites, Rosselia, Rusophycus, Skolithos, and Treptichnus. Characteristics of the facies, lateral and vertical relations between these facies,  associational types of the facies and the depositional profile of the shelf transect  examined show deposition on a wave-dominated carbonate ramp. Integration of ichnologic data with sedimentologic information supports a  firm interpretation of the depositional systems and their evolution. Ethological grouping of the trace fossils resulted from the physico-chemical depositional constraints which defines the proximal-distal ichnofacies gradient pattern of the wave-dominated successions of the Deh-Sufiyan ramp. Considering the obvious deepening of the shallow marine depositional systems of wave-dominated parts of the carbonate ramp, the succession of archetypal ichnofacies can  display a bathymetric trend from deeper to shallower parts, and from lower-to-higher hydrodynamic conditions, from the  bottom to the top of the Unit 2 of the Deh-Sufiyan Formation. The identification and interpretation of the archetypal ichnofacies are  employed to further refine the sedimentary interpretations of parameters such as wave energy, substrate properties, nature of available food supply, salinity, dissolved oxygen content, and variability in sedimentation rates.