Study of ichnofossils and ichnofacies of the upper part of the Shemshak Formation at Tazareh area (North east Damghan)

The upper part of the Shemshak Formation at Tazareh area consists of sandstone, siltstone, and shale beds with marine fossils. Based on systematic study of the ichnofossils in these sediments, 9 ichnogenera, in two assemblages have been identified. The first assemblage with low ichnodiversity (Skolithos, Arenicolites, Diplocraterion) occurs in the siltstone and sandstone beds. This assemblage of ichnofauna represents the skolithos ichnofacies which formed in a relatively high energy condition. The second assemblage with higher ichnodiversity (Planolites, Palaeophycus, Neonerites, Cochlichnus, Rhizocorallium, Chondrites) is very common in the shale beds. This assemblage represents the cruziana ichnofacies which formed in a relatively lower energy condition.