Triassic paleoclimate and paleofloristic trends of southwestern Gondwana (Argentina)

Abstract

Earth's land plants have been shaped by tectonic, climatic and atmospheric evolution for at least 400 million years. The rift basins of Argentina record a continuous record of Triassic paleofloras through a wide paleolatitudinal range offer an opportunity to study the effect of paleoclimate on paleofloral changes through the Triassic period. We review previous work on southwestern Gondwana paleofloras of the Argentinean Triassic System and study the relationship between the palaeobotanical record and the inferred paleoclimatic conditions. The bibliographic review data were used to generate a presence/absence matrix. A cluster analysis, and a principal components analysis (PCA) were carried out to explore relationships among paleofloras. Also, variations in total number of genera per Triassic stage were plotted to elucidate biodiversity trends in the paleobotanical record. Finally, a canonical correspondence analysis (CCA) was performed in order to explore the relationship between the Triassic paleofloristic data and their interpreted paleoclimatic parameters, The influence of potential collection, taphonomic bias, and the uncertainties of the chronostrigraphic framework, on the integrity of the data are discussed. We conclude that the Early Triassic paleofloras developed under arid to semiarid with a marked concentration of seasonal precipitation during the summers; Middle Triassic under semi-arid to sub-humid with precipitation concentration during the summers; and Late Triassic paleofloras during early Carnian developed first under warm humid conditions without marked seasonality but by the Norian and Rhaetian conditions changed to semi-arid with winter rainfall.