Dissertações em Geologia e Geoquímica (Mestrado) - PPGG/IG
URI Permanente para esta coleçãohttps://repositorio.ufpa.br/handle/2011/2604
O Mestrado Acadêmico pertence ao Programa de Pós-Graduação em Geologia e Geoquímica (PPGG) do Instituto de Geociências (IG) da Universidade Federal do Pará (UFPA).
Navegar
Navegando Dissertações em Geologia e Geoquímica (Mestrado) - PPGG/IG por Orientadores "ASP NETO, Nils Edvin"
Agora exibindo 1 - 2 de 2
- Resultados por página
- Opções de Ordenação
Item Acesso aberto (Open Access) Análise integrada da morfologia e sedimentologia do baixo curso do rio Xingu(Universidade Federal do Pará, 2019-01-28) SILVA, Ariane Maria Marques da; ASP NETO, Nils Edvin; http://lattes.cnpq.br/7113886150130994The Xingu River is an important tributary of the Amazon River, contributing with 5% of its total water discharge. Nevertheless, it does not contribute substantially with sediment load. The lower reaches of the Xingu River correspond to a Ria, as a result of the Holocene sea-level rise. It is also classified as a tidal river, where tides reach over 1 m at its confluence with the Amazon River. This study evaluated the morphology and sedimentology of the area, correlating it with hydrodynamics, aiming to understand the still ongoing infilling process of the Xingu Ria. The study area encompasses a stretch of about 180 km, from the Xingu-Amazon river confluence upward to the narrowing of the channel, near the city of Vitória do Xingu. During the maximum sediment discharge of the Amazon River (i.e., feb/2016) 109 bottom sediment samples were collected, whereas 11 of the sampling sites were re-sampled during the minimum water discharge period of both rivers (i.e., nov/2016). During the maximum water discharge period of the Amazon River (i.e., jun/2018), additional water level measurements were undertaken simultaneously in several locations along the Xingu River, as it was also performed during the other campaigns. The morphology was evaluated on the basis of the bathymetric surveys of the Brazilian Navy (CLSAOR/DHN), including about 20,000 points. The results showed that the infilling process of the ria lake has taken place from both ‘ends’ of the area- from the Xingu River itself, forming a prominent bay-head delta, as well as from the Xingu-Amazon River confluence, where tides have transported Amazon River sediments upstream into the Xingu Ria. Furthermore, there is a central portion of the ria lake with large cross-sectional areas, reached only by relatively small amounts of sediments, being a quiescent environment within muddy sedimentation. In a transversal perspective, sands seem to prevail along the margins, where local wave action seem to result in bluff erosion. Longitudinally, sands are substantially more frequent at the bay-head delta area, and at the confluence area, where cross-sections are clearly narrower. Results also suggest that the sediment input from the Amazon River into the Xingu ria has reduced over time, whereas the combination of cross-section area variation and the Xingu River water discharge itself reduce the sediment flux from the Amazon River into the Xingu River.Item Acesso aberto (Open Access) Influência do rio amazonas nos sedimentos de fundo do rio Xingu: evidências mineralógicas e geoquímicas(Universidade Federal do Pará, 2018-12-27) SOUZA, Thiago Pereiras de; SILVA, José Francisco Berrêdo Reis da; http://lattes.cnpq.br/1338038101910673; ASP NETO, Nils Edvin; http://lattes.cnpq.br/7113886150130994The Xingu River is an important tributary of the Amazon River in terms of water discharge, mainly due to its unique morphology and diversified sedimentary dynamics. Hydrodynamic studies record the effect of the tide on the lower Amazon River and its spread on tributaries such as the Xingu and Tapajós rivers, both classified as tidal rivers. These studies support the hypothesis that the Amazon river is a regulating agent in sediment transport and deposition in these environments, acting as a sediment source. In view of this, this work proposed to determine the possible influence area of the Amazon river in the low Xingu river through granulometric, mineralogical and geochemical analysis. The collection points of the bottom sediments obeyed an extensive sampling network that covered 109 transverse and longitudinal collection points of the main and secondary channels of the Xingu River. The granulometric determination was performed with a laser particle analyzer. The mineralogical analyzes consisted of X-ray diffraction data (total sample and clay fraction) and petrographic description of heavy minerals. The total chemical analyzes were performed in total sample for quantification of major elements, traces and rare earth by inductively coupled plasma mass spectrometry (ICP-MS). The results showed that the sediments of the Amazon and Xingu rivers have varying levels of sand, silt and clay and extreme textural variability. The heterogeneity of the textural composition is attributed essentially to the hydrodynamic deposition conditions of the sediments. The mineralogical analysis verified the presence of compositional trends related to clay minerals and heavy minerals, with the association between kaolinite and ultra - stable minerals for samples upstream of the Xingu river and high levels of smectite and unstable minerals for samples from the confluence region between the Xingu and Amazonas , similar to the samples of the Amazon River. Further, the analyzes suggest that the banks of the Xingu estuary act as a third possible source of sediment. Despite the diversity of textured compositions, the sediments of the two rivers did not show significant variations of major elements, traces and rare earths along the sampling stations, but the chemical alteration indexes (CIA) indicated different weather conditions in the sediment source area of the Amazon and Xingu rivers. The statistical treatment of the larger elements, traces and rare earths by PCoA and PERMANOVA, confirmed the differentiation of two large groups of samples of the Amazon River, with similarity to samples from the confluence region with the Xingu River and samples upstream of the Xingu River, corroborating patterns already indicated by the granulometric and mineralogical distribution. According to the analyzes, the influence of the Amazon River on the composition of the bottom sediments of the Xingu River was evident in the entire confluence area with the Amazon River.