Macaronichnus and contourite depositional settings: Bottom currents and nutrients as coupling factors

The trace fossil Macaronichnus segregatis degiberti (7-15 mm in diameter) is recorded for the first time in deep-marine contourites which were deposited in a Late Miocene outer-shelf to upper slope of the Rifian Corridor (Morocco). Macaronichnus is typical of shallow-marine, mainly foreshore environments. It is produced by deposit feeding opheliid polychaetes in high to intermediate latitudes. This record supports the significance of bottom current processes on environmental conditions as a major limiting factor affecting the macrobenthic trace maker community. Mediterranean overflow water during the Late Miocene enabled a high nutrient supply to the seafloor, favouring colonization by Macaronichnus producers. Thus, M. s. degiberti should be used as an indicator for nutrient availability instead of mainly a palaeodepth indicator. This finding provides significant information for oceanographic and environmental reconstructions related to contouritic processes, as well as to contourite characterization.