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

Abstract

Netto, R.G. 2018: An integrative ichnological and taphonomic approach in a transgressive-regressive cycle: a case study from Devonian of Paran a Basin, Brazil. Lethaia, Vol. 51, pp. 15-34.The palaeoenvironmental context of a section of the Devonian Ponta Grossa Formation (Paran a 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. □ Devonian shales, Gondwana, ichnofacies, marine siliciclastic deposits, palaeoenvironmental analysis, taphofacies.Daniel Sedorko ✉ [sedorko@edu.unisinos.br], and Renata G. Netto [nettorg@unisi-nos.br], Geology

Paleoenvironments of a regressive Devonian section from Paraná Basin (Mato Grosso do Sul state) by integration of ichnologic, taphonomic and sedimentologic analyses

“…1A) is represented mostly by transitional offshore to lower shoreface deposits (e.g. Sedorko et al 2018aSedorko et al , 2018bSedorko et al , 2018c. These strata in Paraná state exhibit dominance of expressions of the Cruziana ichnofacies (Sedorko et al 2018c), while in Mato Grosso do Sul state dominates expressions of the Skolithos ichnofacies (this study).…”

“…In the other hand, the Taphofacies 2 has common signatures with the so-called "storm-wave concentrations (type 2)" (sensu Fürsich & Oschmann 1993), grouping well-preserved, monospecific in situ fossils associations. A similar taphofacies was also diagnosed to coeval strata in the southern Paraná Basin (Taphofacies B of Sedorko et al 2018a), representing storm-generated fossil assemblages.…”

“…The Taphofacies 3 has similar signatures of the "condensed concentrations (type 9)" of Fürsich & Oschmann (1993), or with the "Taphofacies C" of Sedorko et al (2018a), the last identified to coeval strata from southern Paraná Basin. These concentrations are described as grouping different taphonomic signatures in the skeletal elements due to in situ reworking and the highest time involved.…”

“…The integration of these tools result in more accurate depositional inferences. However, studies integrating ichnological and taphonomic analysis applied to sedimentological, stratigraphical, palaeoenvironmental and palaeoecological inferences are still rare (e.g., Henderson & McNamara 1985, Bromley & Asgaard 1991, Reolid et al 2014, Sedorko et al 2018a.…”

Devonian Tentaculitoidea of the Malvinokaffric Realm of Brazil, Paraná Basin

“…The Ponta Grossa Formation is composed of black shales, light-gray, dark mudstones, massive to laminated siltstones and interspersed sandy layers with wave or hummocky cross-stratification (Grahn et al, 2013), and trace fossils mainly representing the Cruziana ichnofacies (Sedorko et al, 2018). This unit is characterized by marine deposits of shoreface to offshore environments, in a dominantly transgressive trend (Bergamaschi, 1999;Horodyski et al, 2014).…”