Early Devonian organic-walled phytoplankton from the Ponta Grossa Formation, Paraná Basin, Brazil

Abstract

The depositional succession of the Ponta Grossa Formation (Paraná Basin) corresponds to a wave-dominated shallow-marine environment, represented by four coarsening-upwards cycles, limited by flooding surfaces. Previous studies on a well-preserved and diverse assemblage of miospores indicated a late Pragian to possibly middle Emsian age. The palynological analysis of the Jaciara section is completed herein with the analysis of the marine fraction, composed of highly abundant and diverse organic-walled phytoplankton, with 222 species recognized. Preservation and abundance of some species, that were previously informally described or mentioned, are here formally described. Additionally, two new species are instituted: Pterospermella jaciarense sp. nov. and Florisphaeridium brasiliensis sp. nov. The phytoplankton species, such as Bimerga paula, B. sp. aff. B. bensonii, B. nuda, Cordobesia oriental, C. uruguayensis, Palacanthus ledanoisii, Pyloferites escobaides, P. paranaensis and Winwaloeusia distracta, recorded in the lower part of the section, indicate a late Pragian age, in coincidence with the miospore age. Navifusa spp. and Pterospermella pernambucensis first appear in the middle part of the studied section, suggesting an Emsian age, as do the miospores. The diversity and preservation quality of the phytoplankton tend to decrease towards the top of the section, probably related to a general shallowing trend.