CLASSIFICAÇÃO ALOESTRATIGRÁFICA DO QUATERNÁRIO SUPERIOR NA REGIÃO DE BANANAL (SP/RJ)

Abstract

UPPER QUATERNARY ALLOSTRATIGRAPHIC CLASSIFICATION IN BANANAL REGION (SP/RJ), BRAZIL. Detailed stratigraphic studies, trying to distinguish allostratígraphic units, have allowed the ordenation of late Quaternary deposits found in Bananal region (SP/RJ) through identification of regional discontinuities. The characterization of these discontinuities, essential to understand evolutional dynamics, is based on stratigraphic and geomorphological arguments. The first regional records of Quaternary sedimentation correspond to colluvial deposits named Santa Vitória and Rio do Bananal alloformations. The latter preserves a paleohorizon A, dated in approximately 10.000 years (Pleistocene/Holocene boundary). The first Holocene sediments are fluvial-lacustrine organic clayey deposits called Rio das Três Barras Alloformation, dated in approximately 9.500 years. Following that, another phase of colluviation (Cotiara Alloformation) and a fluvial sandy sequence (Rialto Alloformation) are documented. In clear erosive unconformity above subjacent units, the Manso Alloformation gathers deposits characterized by a great sedimentologic heterogeneity; it contains three facies (Campinho, Quebra-Canto and Fazendinha) closely interfingered. The following sequence of events records an intercalation of colluvial deposits (Piracema and Carrapato alloformations), responsible for recent landscape reworking, and fluvial deposits (Resgate Alloformation), proving other fluvial aggradation phase. The identified deposits represent alternated and/or contemporary events of integrated slopes and streams dynamics that probably transcends Bananal region (SP/RJ).