An integrative ichnological and taphonomic approach in a transgressive–regressive cycle: a case study from Devonian of Paraná Basin, Brazil

Abstract

The palaeoenvironmental context of a section of the Devonian Ponta Grossa Formation (Parana Basin) was examined using an integrated ichnological and taphonomic approach. Three taphofacies (T-A, T-B and T-C) and six ichnofabrics are recognized. T-A is mainly composed of disarticulated organisms and is associated with Chondrites, Planolites-Palaeophycus, Asterosoma-Zoophycos and Asterosoma-Chondrites ichnofabrics, representing the Cruziana ichnofacies. The upward increase in diversity and abundance of body fossils for Taphofacies A can be explained by changes in sedimentation rates during aggradational to progradational phases. T-B beds, represented by articulated brachiopods, occur in distal tempestites associated with the Skolithos ichnofabric (Skolithos ichnofacies) and represent higher hydrodynamic energy and oxygenation than in T-A. Taphofacies C, characterized by a mix of articulated and disarticulated organisms, generally lacks bioturbation except for Chondrites ichnofabrics occurring only at the bed tops, suggesting low substrate oxygenation and low-energy conditions. T-C indicates the maximum transgression in the T-R cycle, characterizing it as a good indicator of maximum flooding surfaces. The composite Asterosoma-Teichichnus ichnofabric (bioturbation degree 5) occurs in layers without body fossils and represents suites of the Cruziana ichnofacies. This likely reflects intense intrastratal activity at all substrate levels, which facilitated the oxygenation of the substrate disallowing the preservation of organism remains. This observation indicates that the bioturbation is an important factor controlling the loss of taphonomic information within the TAZ, mainly when associated with detritus-feeding trace fossils.