%0 Journal Article
%4 dpi.inpe.br/plutao/2012/11.28.16.49.49
%2 dpi.inpe.br/plutao/2012/11.28.16.49.50
%@doi 10.1016/j.sedgeo.2012.09.015
%@issn 0037-0738
%F lattes: 0307721738107549 1 RossettiZanCohCohCre:2012:LaPlWe
%T A Late Pleistocene-Holocene wetland megafan in the Brazilian Amazonia
%D 2012
%A Rossetti, Dilce de Fátima,
%A Zani, Hiran,
%A Cohen, Marcelo,
%A Cremon, Édipo Henrique,
%@affiliation Instituto Nacional de Pesquisas Espaciais (INPE)
%@electronicmailaddress rossetti@dsr.inpe.br
%@electronicmailaddress hzani@dsr.inpe.br
%@electronicmailaddress
%@electronicmailaddress edipocremon@yahoo.com.br
%B Sedimentary Geology
%V 282
%P 276-293
%K tropical wetland megafan, late Pleistocene–Holocene, facies model, residual morphology, monsoonal climate, tectonic subsidence.
%X Despite the growing interest in megafans, definitions provided for this type of environmental setting have not yet been widely agreed upon. A record of sedimentary facies distribution in both space and time including a larger number of analogs is particularly needed for improving megafan facies models. This work focuses on a large fan-like feature from an Amazonian wetland in northern Brazil. Morphological data based on remote sensing, as well as sedimentary facies and radiocarbon analyses, were integrated to propose that this feature is related to a megafan system active during the Late Pleistocene to Holocene. The megafan displays a divergent drainage network, gently-dipping slope, and concave-up and convex-up longitudinal and transverse profiles, respectively. Near surface deposits correspond to fining and coarsening upward sands related to active channels and overbank sand sheets/terminal fan lobes. Sediments are interbedded with abandoned channel/floodplain and lake/pond muds. Morphostructural analyses and drainage anomalies revealed a geological setting affected by reactivation of pre-existing faults contemporaneous with sediment accumulation. Establishment of a megafan system in this wetland most likely occurred within a slightly tectonically subsiding basin under favorable climatic conditions. During wet seasons, high water discharge would have favored sediment transport from highlands into this depositional site. High summer temperatures and drought under a monsoonal regime kept the water levels low. The described megafan could serve as an analog for contemporary tropical wetland megafans formed under a monsoonal climate regime.
%@language en
%3 1-s2.0-S0037073812002758-main.pdf