Differences between autogenic and allogenic expressions of the Glossifungites Ichnofacies in estuarine and shoreface deposits from the Permian of the Paraná Basin, Brazil

Abstract

The Glossifungites Ichnofacies is a substrate-controlled ichnofacies that occurs in omission surfaces and has been used in the identification and interpretation of stratigraphic discontinuities. The Early Permian Rio Bonito-Palermo sedimentary succession from the Paraná Basin (southern Brazil) offers an opportunity to discuss the genesis of the omission surfaces demarked by the occurrence of Glossifungites suites. These suites are composed of sharp, unlined burrows with irregular boundaries and passive infill by generally medium-to coarse-grained sandstones. Thalassinoides is the dominant component in the Glossifungites suites in the studied deposits, with local occurrences of Diplocraterion, Gyrolithes, and Skolithos. Based on the ichnological signatures of the distinct Glossifungites suites observed in these deposits and the characteristics of the facies in which they occur, the associated discontinuity surfaces were interpreted as autogenic or allogenic. The morphological distinction between allogenic and autogenic expressions of the Glossifungites Ichnofacies is observed. Glossifungites suites demarking autogenic surfaces are associated with dewatered muddy substrates from the estuarine settings. Glossifungites suites demarking allogenic surfaces are characterized by large vertical burrows and occur in association with a sequence boundary and coplanar surfaces registered in lower shoreface settings.

Spit bar deposits from the Upper Cretaceous (Cenomanian) transgressive sequence in NE Bohemia (Czechia)

“…They suggested that the large diameter of Thalassinoides is consistent with low-moderate energy conditions in well-oxygenated, nutrient-rich sediments. Similarly, Villegas-Martin et al (2020) suggested that the presence of large burrows in association with allogenic surfaces is a potential firmground signature. The burrow tracemakers, mainly thalassinid crustaceans, were the primary colonizers and probably had sufficient time to explore the exhumed substrates.…”