Programa de Pós-Graduação em Geologia e Geoquímica - PPGG/IG
URI Permanente desta comunidadehttps://repositorio.ufpa.br/handle/2011/2603
O Programa de Pós-Graduação em Geologia e Geoquímica (PPGG) do Instituto de Geociências (IG) da Universidade Federal do Pará (UFPA) surgiu em 1976 como uma necessidade de desmembramento do então já em pleno desenvolvimento Curso de Pós-Graduação em Ciências Geofísicas e Geológicas (CPGG), instalado ainda em 1973 nesta mesma Universidade. Foi o primeiro programa stricto sensu de Pós-Graduação (mestrado e doutorado) em Geociências em toda Amazônia Legal. Ao longo de sua existência, o PPGG tem pautado sua atuação na formação na qualificação de profissionais nos níveis de Mestrado e Doutorado, a base para formação de pesquisadores e profissionais de alto nível. Neste seu curto período de existência promoveu a formação de 499 mestres e 124 doutores, no total de 623 dissertações e teses.
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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) Hidrodinâmica, transporte e proveniência sedimentar no baixo rio xingu e sua importância como “Tidal River” amazônico(Universidade Federal do Pará, 2022-07-14) MEDEIROS FILHO, Lucio Cardoso de; LAFON, Jean Michel; http://lattes.cnpq.br/4507815620234645; ASP NETO, Nils Edvin; http://lattes.cnpq.br/7113886150130994This research is based on the investigation of the processes (geological and hydrodynamic) that govern the recent evolution of a large tributary of the lower Amazon, the Xingu River. The aim was to investigate its aspects of sedimentary evolution and hydrological flows, from already consolidated data on the filling of its ria and how its patterns of transport and sediment trapping, its seasonal and tidal effects have been established, in addition to understanding the role of the Amazon River as a regulator in the dynamics of its tributary. Hydrodynamic measurements of flow, velocity and water level along with bottom sediment and MPS samples were collected at 3 annual seasons (February, June and November). The results provided support for the investigation of the Xingu-Amazonas interaction and the evolution of the bottom morphology of the lower Xingu. The results suggest a filling of the ria both by the Xingu River, forming a prominent headwater delta, and the Amazon River, where tidal variations transport sediments upstream in the Xingu River. On the other hand, large areas in the central part of the ria indicate muddy sedimentation. Elementar geochemistry allowed us to trace part of the history of sediments and source rocks, together with the analysis of immobile elements (Al, Ti, Zr, Hf, Th) and rare earth elements (REE) because they are poorly fractionated during weathering processes. and they are concentrated in the bottom sediments to the detriment of the dissolved fraction of the rivers. The deposits preserved in the lower Xingu River, despite draining cratonic regions in higher areas, confirm that the bottom material is derived from heterogeneous sources with predominantly intermediate igneous compositions and that they underwent important recycling during fluvial transport. The hydrodynamic modeling allowed to indicate the fluvial discharge as the most relevant forcing for the muddy deposition dynamics in the Xingu estuary. From a numerical model, it was possible to extrapolate the flow and transport dynamics beyond the open boundaries, that is, the central portion of the ria, elucidating the interaction mechanism between river and tidal discharge and the associated sedimentary dynamics. The determination of the amplitudes and phases of the tidal components, whether of purely astronomical origin or resulting from shallow waters, as well as the average level and the hourly discharge proved to be fundamental for the understanding of the governing processes.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.Item Acesso aberto (Open Access) A pluma do rio Amazonas: fonte: dinâmica e transporte de sedimentos para estuários e manguezais do litoral leste amazônico.(Universidade Federal do Pará, 2024-06-14) SILVA, Ariane Maria Marques da; ASP NETO, Nils Edvin; http://lattes.cnpq.br/7113886150130994; https://orcid.org/0000-0002-6468-6158The Southeastern Amazon Coastal Zone (SACZ) includes the largest mangroves belt in the world and more than 20 macrotidal estuaries. In this area, a large volume of fine sediments has been deposited during the Holocene, however, it is known that the local rivers are black water rivers, carrying small amounts of suspended sediment. Therefore, since decades the sources and transport mechanisms of fine sediments to estuaries and mangroves have been speculated and investigated. It was recently demonstrated the existence of an offshore source of muddy sediments to the mangroves. Due to its proximity, the Amazon River has been seen as the probable main source of sediments, where an average flow of 170x103 m3 .s-1 and suspended sediment concentrations in the order of 80 mg.L-1 would represent a nearly inexhaustible source of mud to both estuaries and mangroves. However, the provenance and transport processes by which the mud of the Amazon would reach the SACZ, providing mangrove progradation, are not yet understood, since the plume is mostly drifted to northwest. In this context, the sedimentary constitution of the inner continental shelf and its reworking must also be evaluated, as well as the possibility of mud supply to the east of the study region. The present study aimed to integrate and complement efforts on sediment dynamics in the estuaries (Mocajuba, Caeté and Gurupi) and mangroves of the SACZ, combining studies on the inner continental shelf. Therefore, tools and approaches from hydrodynamics, sedimentology and biogeochemistry were used to identify and understand the sources and transport mechanisms of muddy sediments for the sector, composing a distance gradient from the mouth of the Amazon River, as well as a gradient of the drainage basins size. The Mocajuba estuary presents quite peculiar aspects in terms of morphology and hydrodynamics. The morphology of the estuary is strongly influenced by structural evolution and faults caused by neotectonic events since the Neogene, resulting in deep and straight areas in the lower and middle portions of the estuary. The tide propagates into the estuary without significant deformations, as a result of the combination between inherited morphology and hydrodynamic aspects. Salinity showed higher values during dry seasons, while the concentration of suspended sediment was higher during rainy seasons. Estuarine circulation in Mocajuba is similar to fjord because of the deep, however, without salinity stratification. The estuarine turbidity maxima zone did not occur due to the high depth areas, low current velocities, and low suspended sediments concentration. However, a “high turbidity wedge” was observed near the mouth of the estuary, evidencing the Amazon River plume influence. The Caeté estuary is classified as a coastal plain, tide-dominated, with a semidiurnal regime and considerable variations during the spring and neap phases. From a scientific point of view, this is one of the most studied estuaries in the SACZ, including geology, geomorphology, hydrodynamics, sedimentology, geochemistry, biogeochemistry, ecology in general, among other studies areas. For this Thesis, the Caeté estuary was considered a “model estuary” due to its geographic location (regarding to the Amazon River mouth, Mocajuba and Gurupi estuaries distances), the hydrographic basin size and especially because of the data available in scientific articles that prove the influence of an offshore source of fine sediments. Gurupi is a typical coastal plain estuary, shallow, funnel-shaped, tide-dominated, but partially mixed. Salinity levels and suspended sediment concentrations were higher at the mouth and decreased upstream. The estuarine turbidity maxima zone was observed in both seasons, however, the increase in river discharge, during the rainy season, attenuated and displaced this zone seaward. The tide propagated asymmetrically, with hypersynchronous behavior near the mouth, being attenuated upstream. Regarding sedimentary organic matter, the data showed that estuarine samples present more negative δ13C values, as a result of stronger terrestrial and mangroves influences. The δ13C values of samples collected on the inner shelf showed less negative values, indicating a mixture between marine and mangrove carbon sources. Furthermore, the results showed that the size of the drainage basin of local rivers is also a relevant factor in the dynamics of organic matter. The Gurupi River, for example, is large enough to contribute organic and terrigenous sediments to the estuary and internal shelf. In summary, the SACZ estuaries are characterized by the macrotidal regime, subject to singular aspects of geology, geomorphology and the local river. In the Mocajuba estuary, inherited morphology had a strong influence on hydrodynamic and sedimentary processes. In the Gurupi estuary, the high river flow played a fundamental role in the estuarine dynamics.