Ichnological analysis and depositional setting of late Miocene marginal marine deposits from the Tafna Basin (northwestern Algeria)

Abstract

Abstract The late Miocene marginal marine deposits of the Sikkak area (Tafna Basin, northwestern Algeria) encompass moderately diversified invertebrate trace fossils preserved mainly as epichnia. The present study documents for the very first time the trace fossils occurring in this area, where 16 ichnotaxa, dominated by post-depositional domichnial, repichnial and fodinichnial components, are reported: ? Bifurculapes isp., Diplocraterion isp., Helminthoidichnites isp., ? Kouphichnium isp., ? Megagrapton irregulare , Ophiomorpha annulata, Ophiomorpha cf. nodosa , Oravaichnium isp., Palaeophycus isp., Planolites cf. beverleyensis , Planolites montanus , Ptychoplasma isp., Skolithos isp., S. linearis , Thalassinoides isp. and T. suevicus . The main producers of the studied trace fossils are arthropods (crustaceans, limulids, insects), annelids (polychaetes, phoronids) and bivalves. These traces are commonly associated with sedimentary structures that are caused by hydrodynamics, suggesting high-energy conditions and opportunistic colonization within a marginal marine environment (i.e. backshore to foreshore), and corresponding to the Skolithos ichnofacies. The crustacean trace ? Bifurculapes and the limulid trackways Kouphichnium are reported herein for the first time in Algeria. Sedimentological data suggest an imbricated sandstone channel within a marginal marine setting and subaerial exposures indicated by mud-cracks. The foraminiferal assemblage, dominated by shallow marine species, therefore suggests a Tortonian age for these deposits.