Caracterização de depósitos fluviais de grandes e pequenos rios no Quaternário da Amazônia: Terraços de terra firme no Médio Rio Solimões, Amazonas (AM) e a formação Boa Vista, Roraima (RR)

Abstract

STERN, André Gainotti. Characterization of fluvial deposits of large and small rivers in the Quaternary of the Amazon: Terra Firme Terraces in the Middle Rio Solimões, Amazonas (AM) and the Boa Vista Formation, Roraima (RR). 2019. 122 p. Tese (Doutorado

First record of plant macrofossil from the Boa Vista Formation, Takutu Basin, Roraima State, Brazil

“…The landscape began to be exposed to weathering forming an intertwined fluvial system of distributary sandy bars, transporting the fine sediments that were deposited throughout the physiographic domain that today composes the Boa Vista Formation, resulting in the extensive pediplain that characterizes the central-northwest region of the State of Roraima (Menezes et al, 2020). The Optically Stimulated Luminescence dating of the upper unit of the Boa Vista Formation places the deposition of this unit in the Late Pleistocene-Holocene (Stern, 2019;Zular et al, 2019;Oliveira, 2020).…”

“…The Boa Vista Formation is considered a heterogeneous unit both spatially and vertically in terms of faciological composition. Recent studies describe it as a relatively shallow sedimentary unit, whose thickness changes according to the conformation of the basement, ranging from 15 to 120 m. It is constituted by two semi-consolidated sedimentary successions, the lower, composed of gravels with grains of varying sizes (between granule and boulder), and the upper one, composed of ferruginous sands slightly conglomeratic and silty-sandy deposits (Stern, 2019;Menezes et al, 2020). According to Barbosa & Andrade-Ramos (1959) the Boa Vista Formation can be characterized as a set of layers of sand and, secondarily, laterite and mud, sometimes with intercalations of sandy to muddy layers, with gravel to pebbly levels, frequently with lateritic concretions.…”

“…In order to find more evidence of this correlation, the present study carried out the systematic collection of samples from two outcrops close to the fossil collection area and the results obtained suggest that the fossils correspond to the Boa Vista Formation. This unit almost completely covers the Takutu hemigraben region (Eiras & Kinoshida, 1990) and has its deposition attributed to the Late Pleistocene-Holocene interval (Stern, 2019;Zular, 2019;Oliveira, 2020).…”