Palynology of the Tertiary sediments of the São Paulo Basin, State of São Paulo, Brasil

Abstract

The Tertiary sediments of the São Paulo Basin, which include the São Paulo and Itaquaquecetuba Formations, have been recently interpreted as a Paleocene sedimentary ensemble comprising: a basal alluvial fan to braided-stream system; a partially contemporaneous lacustrine system; a meandering fluvial system at the top of the sequence. The origin of the Itaquaquecetuba Formation (braided-channel system) is controversial, and it has been considered by different authors as having been associated with the basal deposits of the basin and as due to tectonic reactivation and sediment reworking during the Neogene or Quaternary. This study comprises the palynological analysis of sediments from the alluvial fan, laustrine and braided-stream systems (this latter attributed to the Itaquaquecetuba Formation); the respective palynofloras are homogeneous and include several taxa of stratigraphic and paleoclimatic value, suggesting very close ages and climates. The dorninance of Oligocene taxa together with only a few others considered as Eocene or older suggest two hypothesis: 1) possible reworking of Eocene sediments in the Oligocene; 2) the taxa previously considered as Eocene in age may have, in fact, lived until Oligocene, and so should have their distribution interval suitably corrected. The relative abundance of taxa indicating colder climates (conifers) and the scarcity of others more typical of hot and wet climate suggests that sedimentation took place under cold conditions. However, it was not possible to establish precisely the influence of altitudinal floristic differentiations in the preserved palynological assemblage