Simplified geological map, with the location of the study area in the northeast of the state of Pará and the lithostratigraphic profiles (1 to 12) that provided the samples dated in this study. Observe the triangular morphology of the Post-Barriers Sediments related to the filling of a paleovale, which starts in the city of Tucuruí and amplifies to NNW towards Marajó Island.
Outcrop examples illustrating the studied deposits. A) General view of profile 1 (Praia dos Aruãs), where the Post-Barriers Sediments occur discordantly on a discontinuity surface (black arrows) marked by erosion and lateritic paleosol, which is characterized, at the top, by ferruginous concretions. This paleosol is developed on the Barreiras Formation. B) Detail of the discontinuity surface seen in figure A. C) Profile 8 (Abaetetuba), illustrating the succession Pirabas / Barreiras inferior being overlapped by discontinuity surface (arrows), highlighted by abundant root marks. Above this, the Barreiras Medio / Superior Formation occurs, quite weathered, which is overlapped discordantly (dotted line) by the Post-Barriers Sediments. Lateritic concretions are absent at this location, but they appear laterally in the profile. D) Detail of figure C, illustrating the discontinuity surface (arrows) at the top of the Pirabas / Barreiras Formation, marked by abundant root marks.
Sonia H. Tatumi1, Luis P. da Silva1, Elcio L. Pires1, Dilce F. Rossetti2, Ana M. Góes3 &
Abstract The Barreiras Formation in the northeastern state of Pará is discreetly covered by a variety of
oxidized strata, light red to pale yellow in color, whose ages are
and, when possible, 14C, it can be seen that the formation of these strata occurred at the end of the Pleistocene
young people, and significant differences for relatively older ages. The fact that the strata aged
at the time of deposition, reflecting the radiation acquired at depositional sites prior to its last
tions. The Barreiras Formation exposed in the northeastern of the State of Pará, overlain by a variety of
oxidized, light red to pale yellow strata, whose ages are presented, for the rst time, in the present work. Based
conclude that the formation of these strata took place at the end of late Pleistocene to Holocene, with recorded
LOE / MAR ages ranging from 430,000 (± 60,000) to 3,400 (± 400) yr BP. A comparison of OSL / MAR and
differences for deposits with relatively older ages. The fact that strata with older ages show evidence for deposit-
sition under sub-aqueous conditions led to conclude that the differences obtained here is more likely due to
ages, and integrating these data with information derived from previous publications, it can be concluded that
the Post-Barreiras Sediments record deposition at the margin of a wide paleovalley, which display its main
1 – Faculty of Technology of São Paulo – FATEC, São Paulo (SP), Brazil. Email: (hidden)
2 – National Institute for Space Research – INPE, São José dos Campos (SP), Brazil. Email: (hidden)
3 – Post-Graduate Program in Geochemistry and Geotectonical Sedimentary and Environmental Geology University of São Paulo-USP, Institute of
… The origin of these features varies between pedological processes forming sandy depressions (Moreau et al.