Exploring Ichnofacies Distribution in Ancient Seaways: The Late Miocene Rifian Corridor as a Natural Laboratory

Oceanic gateways have modulated ocean circulation and have influenced climatic variations throughout the Earth´s history. During the Late Miocene (7.8 - 7.35 Ma), the Atlantic Ocean and the Mediterranean Sea were connected through the Rifian Corridor (Morocco). This gateway is one of the few examples of deep ancient seaways with a semi-continuous sedimentary record. Deposits comprise turbidites intercalated between deep-sea fine grain sediments (i.e., hemipelagites and drift deposits), channelized sandstone contourite facies, and shallow marine sandstones. Herein an ichnological analysis was conducted in these upper Miocene sediments to improve characterisation of palaeoenvironmental conditions. In addition, ichnofacies were analysed to elucidate how bottom currents control ichnofacies distribution and can modified their attributes. Turbidite deposits are typified by vertical trace fossils (i.e., Ophiomorpha ), conforming the Ophiomorpha rudis ichnosubfacies. Contouritic sandstones exhibit high density and low diverse trace fossil assemblage, with predominant Macaronichnus and Scolicia, resembling a proximal expression of Cruziana ichnofacies. Shallow marine environments are dominated by vertical trace fossils (e.g., Conichnus , Ophiomorpha and Skolithos ), allowing an assignation to Skolithos ichnofacies. This study reveals energy to be a major controlling factor determining ichnofacies attributes and distribution in ancient deep seaways. Within these seaways, highly energetic conditions typical of shallower settings are present in deeper environments (i.e., slope), contributing to ichnodiversity impoverishment in ichnofacies.