LOWER PERMIAN POST-GLACIAL SUCCESSION IN THE SOUTHERN BRAZILIAN PARANÁ BASIN: AN OVERVIEW OF STRATIGRAPHIC AND BIOSTRATIGRAPHIC FRAMEWORKS

A synthesis of paleobotanic and palynologic successions in Lower Permian strata of the Paraná Basin in the State of Rio Grande do Sul State is presented based on new data and previously established zonations. The Upper Itararé Group, Rio Bonito, and Palermo Formations, the units of this stratigraphic interval, were formed in distinct pro- and post-glacial environments (glacio-marine, fluvio-deltaic, shallow marine). Detailed sequence stratigraphic analysis of the Lower Permian strata within the study area has shown that there are three third order sequences representing important regional base-level changes which generated clear wide-spread unconformities. In terms of biostratigraphy, two interval palynozones and two assemblage plant macrofossil zones characterize this interval; in ascending order, these are the Vittatina costabilis and Lueckisporites virkkiae palynozones, and the Botrychiopsis plantiana, and Glossopteris / Rhodeopteridium plant macrofossil zones. This contribution aims to present a first integrative overview on the sequence stratigraphic and biostratigraphic frameworks proposed mostly on the basis of Lower Permian sections from Rio Grande do Sul State, establishing the correlation among stratigraphic sequences, palynozones and plant zones. The turnovers of palynofloras seem to be driven by climatic changes on a regional scale while the rise of diversity in plant assemblages appears to be due to changes in the depositional settings through the interval under consideration. Thus, part of the plant zones apparently corresponds to distinct ecofacies, being better regarded as ecozones rather than as biozones. On the other hand, significant changes in palynofloras occur slightly below maximum flood events within the Parana Basin, which correspond in theory to warm intervals that follow the cold/cool temperate conditions recorded mainly in Western Australia on the basis of marine faunas. In this case, the palynofloral turnovers and/or flooding events could be useful for intra-continental correlations throughout Gondwana during Early Permian times.