Interpretações paleoclimáticas a partir da tafoflora de Caieira, Formação Pirabas, Oligoceno/Mioceno da Amazônia Oriental, Pará, Brasil

Abstract

Paleoclimatic interpretations from the Caieira taphoflora, Pirabas Formation, Oligocene/Miocene of the eastern Amazonia, Pará, Brazil. The Caieira taphoflora, which is associated with the Pirabas Formation, is the best documented one for the Oligocene/ Miocene of the eastern Amazonia. The taphoflora represents a predecessor of a phytophysiognomy of the Amazon Forest, specifically of a floodplain forest, which has developed under a warm and humid climate. The main physiognomic characteristics-type of margins and leaf area-of the angiosperm leaves of 19 species of this taphoflora, allowed us to carry out the reconstruction of the mean annual temperature (MAT) and the mean annual precipitation (MAP) for the moment of its deposition. The different equations used to reconstruct the MAT and the MAP are based on univariate methods known as Leaf Margin Analysis and Leaf Area Analysis. These equations indicated that the Caieira taphoflora developed under a MAT between 24.6 and 25.0 °C, and a MAP between 1849 and 2423 mm. The values are similar to the current values for the region where the taphoflora was collected, therefore, it is possible to infer that the current climatic configuration has been firmly established since the Oligocene/Miocene, as well as its vegetation. The values also indicate that the climate was colder, between 1.1 and 1.5 °C, and less humid, between 42 and 619 mm, for the moment of deposition of the Caieira taphoflora, possibly due to the global cooling event known as Mi-1 glaciation, which affected the whole Amazonia during the Oligocene/Miocene transition.