Application of digital image treatment to the characterization and differentiation of deep-sea ichnofacies

The ichnofacies model proposed by Seilacher in the 1960's stands as one of the main tools used in the ichnological research. Based on the integration of numerous ichnological and sedimentological observations, it entails a precise characterization of the trace fossil assemblage. Differentiation of trace fossils may be relatively easy in outcrops, but cores are a different matter, particularly modern marine cores. Difficulties are even more accentuated in deep-sea pelagic and hemipelagic, non-turbiditic, fine-grained deposits. The application of digital image treatment can facilitate trace fossil identification and improve deep-sea ichnofacies characterization on modern cores. The method proposed here was applied to cores from the IODP Expedition 339 (Site U1385). Eight ichnotaxa—Chondrites, Palaeophycus, Phycosiphon, Planolites, Taenidium, Thalassinoides, Thalassinoides-like structures and Zoophycos—as well as some horizontal grouped circular structures interpreted as trails (?Nereites) were recognized. The archetypical Zoophycos ichnofacies is identified, but characteristic elements belonging to the Nereites ichnofacies and to the distal expression of Cruziana ichnofacies are locally recognized. Thus, the applied methodology allows differentiating between different expressions of the Zoophycos ichnofacies and to approach subtle changes in the involved environmental parameters affecting tracemakers.