Sedimentary substrate and trace fossil assemblages in marine Pliocene deposits in Northeast Spain

The trace fossils in the marine Pliocene of the Baix Llobregat area display a strong relationship to their host sediment. Clays include syndepositional traces belonging to Domichnia (Ophiomorpha nodosa, O. annulata and O. irregulaire) and Fodinichnia (Rosselia socialis). The trace fossils in sandstone layers are postdepositional and may be included in the groups Fodinichnia (Thalassinoides suevicus), Pascichnia (Neonereites uniserialis, N. biserialis, Laminites sp. and Planolites montanus) and Cubichnia (Cardioichnus sp.). This relationship is the consequence of several characteristics of the sedimentary substrate, that are strongly influenced by grainsize (oxygenation, amount of organic matter). The way in wich the storm beds were colonised also played an important role.