Are early plants significant as paleogeographic indicators of past coastlines? Insights from the taphonomy and sedimentology of a Devonian taphoflora of Paraná Basin, Brazil

Abstract

The continental colonization process by plants is an underexplored theme in Brazil, especially concerning taphonomic studies of plants that existed during this age. This study aims to interpret the taphonomic and paleoenvironmental settings that best represent the fossil plant assemblages preserved in the upper strata of the Furnas Formation (Lower Devonian of Paraná Basin), at Jackson de Figueiredo county, municipality of Jaguariaíva (Paraná), clarifying the potential of these fossil plant assemblages for paleogeographic reconstructions. Taphonomic and sedimentological signatures were analyzed and submitted to multivariate statistical analyses (cluster and correspondence analyses). Two taphonomic groups were identified (Taphofacies A and B). The interpretation of the two groups allowed the visualization of: Taphofacies A, which consists of samples with a dispersed degree of packing, fragmented plant fossils, 40% mica with sizes between 0.5 and 1 mm and no trace fossils, is representative of relatively high-energy conditions; and Taphofacies B, which consists of densely packed plants with partial degree of fragmentation, 10% mica with sizes under 0.5 mm and both horizontal and vertical trace fossils, is representative of relatively low-energy conditions. Our taphonomic data are consistent with previous facies interpretations of a lagoon/interdistributary bay environment. In this context, taphofacies A represents episodic sedimentation events influenced by fluvial dynamics, yielding assemblages that are not suitable for paleogeographic interpretations, while Taphofacies B represents fossil assemblages originated in a low-energy sedimentary regime, with utility for paleogeographic reconstructions.