Reconstructing deltaic palaeoenvironments in southern South America: phytoliths in Miocene estuarine sediments (Paraná Formation)

Abstract

This study provides new insights into the palaeoenvironments that developed during the Late Miocene in Argentina and represents the first palaeobotanical record for the Parana Formation at the Salto Ander Egg site. The analysis of the phytolith assemblages identified new morphotypes not previously documented in the literature for the sediments of this region. The importance of these discoveries lies in their potential taxonomic relevance to plant components associated with mangrove environments. The stratigraphic column in the study area is made up of the Parana´ Formation (Late Miocene) and other Neogene and Quaternary geological formations. Samples of three sedimentary cycles were taken for the analysis of the phytoliths in levels with internal discontinuities and a high density of sub-vertical tubular biogenic structures and horizontal extensions. The morphotypes identified suggest the presence of species with pneumatophores, features typically found in intertidal mangrove forests. This study highlights the potential of phytolith analysis as a valuable tool for characterising deltaic palaeoenvironments. The phytolith assemblages from the Parana´ Formation sediments provide important preliminary insights into a palaeoenvironment that possibly included mangrove forests and saline-adapted plant communities, existing in an ecosystem with freshwater availability within a saline environment, under a warm tropical to subtropical climate.