Multitemporal analysis of the Solimões-Amazonas river system between the Purus and Negro tributaries, Western Amazon, Brazil

The geomorphological features of some stretches of the Solimões-Amazonas river system have been studied in the past decades by means of remote sensing images combined with multitemporal analyses, which mainly highlighted the morphological changes in the system’s floodplains and channels. Early studies used cartographic databases less accurate than the current ones and did not take into account certain factors, such as the contours the river valley, sensor type, and data inaccuracy and incompleteness, thus reducing accuracy. Currently, channel migration rate and definition of the fluvial style in different river stretches, which vary amongst the most well-known types in literature, stand out among the most emphasized factors in the analysis of this river system. This work demonstrates, by means of multitemporal analysis of Landsat-5/TM images, the final stage of evolution of the Solimões-Amazonas river system, in the stretch between the Purus and Negro tributaries, from 1991 to 2011. Interpretations point out a slight predominance of depositional processes relative to the erosive ones along the analyzed stretches, covering areas of 8.56 km2 and 6.86 km2, thereby attaining a mean migration rate of 0.32%/year. The depositional processes are mainly concentrated on the convex part of the meanders and areas downstream of the islands, including the formation of new islands, the erosive on the concave part of the meanders and upstream the islands. Despite the erosion and deposition dynamics observed in the study areas, it was possible to ascertain a high stability pattern for the channels, which showed to be consistent with the bathymetric data and migration rate values found during regional geological studies, which helped characterize the current river style as anabranching.Nas últimas décadas, as feições geomorfológicas de trechos do sistema fluvial Solimões-Amazonas têm sido estudadas por meio de imagens de sensores remotos, aliados a dados de análise multitemporal, destacando principalmente as modificações morfológicas das planícies aluviais e canais deste sistema. Os primeiros estudos utilizavam bases cartográficas de menor precisão em comparação às atuais e não consideravam alguns fatores como a cota dos rios, tipos de sensores e imprecisões na aquisição dos dados, o que diminui a acurácia dos dados. Atualmente, dentre os fatores mais enfatizados na análise desse sistema fluvial, destacam-se a taxa de migração dos canais e a definição do estilo fluvial em diferentes trechos, que variam entre os tipos mais conhecidos na literatura. Este trabalho demonstra por meio da análise multitemporal de imagens Landsat-5/TM a fase final de evolução do sistema fluvial Solimões-Amazonas, no trecho entre os tributários Purus e Negro, no decorrer dos anos de 1991 e 2011. As interpretações indicam leve predominância dos processos deposicionais em relação aos erosivos no trecho analisado, com áreas de 8,56 km2 e 6,86 km2, respectivamente, obtendo-se assim uma taxa de migração média de 0,32%/ano. Os processos deposicionais se concentram principalmente na parte convexa dos meandros e nas áreas a jusante das ilhas, incluindo a formação de novas ilhas, e os erosivos na parte côncava dos meandros e a montante das ilhas. Apesar da dinâmica de erosão e deposição observada no trecho estudado deste sistema, foi possível constatar o elevado padrão de estabilidade dos canais, o qual é coerente com dados batimétricos e de taxa de migração de estudos geológicos regionais, que ajudam a caracterizar o atual estilo fluvial anabranching

Subsurface stratigraphy of the cretaceous-neogene sedimentary sequence of Manaus and Itacoatiara regions, Central Amazon

O arcabouço estratigráfico pós-paleozoico da região de Manaus e Itacoatiara (Amazônia Central) foi elaborado com base em quatro seções geológicas contendo principalmente dados geofísicos e litológicos de 15 poços tubulares com até 300 m de profundidade, complementado com descrições de afloramentos. A definição de padrões específicos das curvas de raios gama natural (RG) e resistividade (RE) permitiu a individualização das unidades sedimentares inferior, intermediária e superior e seus contatos (descontinuidades S1 e S2). A unidade inferior, definida a partir da cota de -130 m, é constituída principalmente de folhelho, cujas repetições diagráficas das curvas de RG e RE caracterizam os padrões de curva tipos funil e serrilhado. A unidade intermediária, definida nas cotas entre 20 a -180 m, é constituída por intercalações de arenitos, pelitos e conglomerados, que geram repetições cíclicas de valores das diagrafias de RG e RE, gerando os padrões serrilhado e sino. A unidade superior, definida na cota de -30 m até a superfície do terreno, é constituída principalmente de arenitos com intercalações restritas de pelitos, que definem os padrões simétrico (curva de RG) e caixote (curvas de RE e RG). O posicionamento estratigráfico das unidades inferior, intermediária e superior nas seções, bem como o aspecto litológico e as relações com as superfícies limitantes, aliado a dados estratigráficos e geocronológicos regionais permitiram sua respectiva associação com as formações Nova Olinda-Andirá (Paleozoico), Alter do Chão (Cretáceo) e Novo Remanso (Neógeno) da Bacia do Amazonas. Em função da densa cobertura de vegetação e solo, os aspectos litológicos e padrões diagráficos descritos para cada unidade podem servir de base para o estudo da cobertura sedimentar pós-paleozoicas da AmazôniaThe post-Paleozoic stratigraphic setting of Manaus and Itacoatiara area (central Amazonia) was developed based on four coross-sections containing geophysical and lithological data from 15 wells, up to 300 m deep, and outcrop description. Gamma ray (GR) and electric resistivity (ER) patterns allowed the separation into lower, intermediate and upper sedimentary units, and their contacts (S1 and S2 surfaces). The lower unit, starting at -130 m, is composed by carbonatic shale, with characteristic funnel and serrated GR and ER patterns. The intermediary unit occurs between 20 and -180 m, and is composed by sandstones with intercalated silt and claystone, with scattered layers of conglomerate. These intercalations generate cyclic repetitions of GR and ER values, creating a serrated and bell-type patterns. The upper unit occurs from -30 m to the surface and is composed by sandstone with scattered silt- and claystone, generating symmetrical (GR) and box-type (ER and GR) patterns. The stratigraphic position, lithological composition and the contact surfaces of the lower, intermediate and upper units allow us to associate them with the Nova Olinda-Andirá (Paleozoic), Alter do Chão (Cretaceous), and Novo Remanso (Neogene) formations of the Amazon Sedimentary Basin. Weathering and vegetation are always a challenge for geologic mapping the Amazon. Thus, the geophysical patterns and lithological aspects described in this paper may well serve as a good starting point for determining post-Paleozoic formations and their contact surfaces in the Amazon Sedimentary Basi

Late Holocene paleoenvironments of the floodplain of the Solimões River, Central Amazonia, based on the palynological record of Lake Cabaliana

The core PD-67 of 160 cm depth was collected from the delta of Lake Cabaliana situated on the Solimões River. Seventeen samples were removed for palynological and sedimentological analysis and three for radiocarbon analysis. Two dry periods, both in the Late Holocene, were observed (2800-2550 cal yr BP, 1450-550 cal yr BP) separated by a wetter phase (2550-1450 cal yr BP). In 2800-2550 cal yr BP, varzea forests of Alchornea, Symmeria, Cecropia, Alternanthera and Asteraceae were predominant. Beginning in 2,550-1450 cal yr BP, the varzea was characterized by pioneer elements, such as Cassia, Laetia, Mabea, Symmeria and Cecropia, and by the expansion of Poaceae, Cyperaceae, Sagittaria, Montrichardia and Asteraceae. In 1450-550 cal yr BP the succession of varzea continued with Pseudobombax, Laetia, Luehea/Lueheopsis and Ryanaea increasing simultaneously with the terra firme vegetation of Rutaceae, Sapotaceae, Styrax, Scleronema, Anthurium, Araceae, pteridophytes and Pariana. The successional dynamics at Lake Cabaliana indicated that the local varzea had become established recently, and is composed of a mosaic of different successional stages of vegetation influenced mainly by flood pulse and variation in rainfall. It is therefore possible to propose that the recent climate history of Central Amazonia reflects changes in rainfall patterns in the basin

PALINOLOGIA DA FORMAÇÃO CODÓ, BACIA DO PARNAÍBA: IDADE E PALEOAMBIENTE DEPOSICIONAL: Palynology of Codó Formation, Parnaíba Basin: age and depositional paleoenvironment

Os depósitos siliciclásticos da Formação Codó possuem significativo potencial para geração de hidrocarbonetos no Cretáceo Inferior da Bacia do Parnaíba. Da análise do conteúdo palinológico de 44 amostras do poço 9-PAG-8-MA, foi possível tecer considerações relacionadas ao seu posicionamento temporal e identificar seu paleoambiente deposicional e respectivo paleoclima. Foram identificadas 96 espécies de palinomorfos, predominantemente de origem continental. A presença das espécies-guia Sergipea variverrucata e Equisetosporites maculosus permitiram posicionar bioestratigraficamente os estratos nas palinozonas Sergipea variverrucata (P-270) e Complicatisaccus cearensis (P-280), correspondendo ao neoaptiana. Dinocistos do gênero Subtilisphaera atestam a ocorrência de ingressões marinhas ao longo da sedimentação. Os sedimentos depositaram-se em um ambiente dominantemente continental (flúvio-lacustre), gradando para um ambiente transicional costeiro a marinho restrito, com registros de ingressões marinhas e sob um paleoclima árido a semiárido, evidenciado pelo predomínio de grãos de pólen dos gêneros Classopollis, Gnetaceaepollenites e Equisetosporites. O aumento na frequência relativa dos gêneros Crybelosporites e Cicatricosisporites, observado em dois níveis estratigráficos, sugerem momentos de semiaridez ao longo da deposição, que podem estar relacionadas a redução na salinidade, visto o aumento da frequência relativa de Afropollis e diminuição de Classopollis. O conteúdo palinoflorístico identificado apresenta características que permitem o enquadramento na província palinoflorística a Dicheiropollis etruscus/Afropollis

CONTEXTO ESTRATIGRÁFICO E ANÁLISE DE MINERAIS PESADOS DA MEGASEQUÊNCIA SEDIMENTAR CRETÁCEA-NEÓGENA AFLORANTE NA PORÇÃO OESTE DA BACIA DO AMAZONAS, AM: Stratigraphic context and heavy mineral analysis of the Cretaceous and Neogenous sedimentary units in the western portion of the Amazon Basin, AM

In the western portion of the Amazon Basin, the Mesozoic-Cenozoic siliciclastic rocks megasequence of the Javari Group spring up, formed by the Alter do Chão and Novo Remanso formations, characteristic of fluvial depositional paleoenvironments. They exhibit the best exposures in Manaus, Iranduba, Manacapuru, Novo Airão, Careiro Castanho, Itacoatiara, Beruri, and Presidente Figueiredo municipalities where they are possible to visualize the discordant contact between the units despite the challenge in individualization due to the sedimentary facies’ similarity. Associated with palynological and regional paleosurface data, the application of the heavy minerals’ method has proved to be a crucial tool in defining the Cretaceous-Neogene stratigraphic framework in the western portion of the Amazon Basin owed to the defined mineralogical differences. While the Cretaceous unit is composed of an ultra-stable assemblage with zircon, tourmaline, and rutile grains (ZTR index), the Neogene one stands an ultra-stable to unstable assembly with ZTR grains, in addition to sillimanite, staurolite, kyanite, epidote, apatite, topaz, and hornblende. The differences observed were associated with distinct source areas of the Amazon Craton, which were reworked during the implementation of the Cretaceous and Neogene drainage paleosystems in the Amazon Basin, which migrated west and east, respectively.Na porção oeste da Bacia do Amazonas afloram rochas siliciclásticas da megassequência mesozoica-cenozoica do Grupo Javari, formado pelas formações Alter do Chão e Novo Remanso, característicos dos paleoambientes deposicionais fluviais. Exibem as melhores exposições nos municípios de Manaus, Iranduba, Manacapuru, Novo Airão, Careiro Castanho, Itacoatiara, Beruri e Presidente Figueiredo, onde é possível visualizar o contato discordante entre as unidades, apesar da individualização ser dificultada em função da similaridade de fácies sedimentares. Associado aos dados palinológicos e de paleosuperfícies regionais, a aplicação do uso de minerais pesados tem se mostrado uma ferramenta importante na definição do arcabouço estratigráfico Cretáceo-Neógeno da porção oeste da Bacia do Amazonas, em função das diferenças mineralógicas definidas. Enquanto a unidade cretácea é composta por uma assembleia ultra estável com grãos de zircão, turmalina e rutilo (índice ZTR), a neógena apresenta uma assembleia ultraestável a instável, com grãos de ZTR, além de silimanita, estaurolita, cianita, epídoto, apatita, topázio e hornblenda. As diferenças observadas foram associadas a áreas fontes distintas do Cráton Amazônico, as quais foram retrabalhadas durante a implantação dos paleosistemas de drenagem no Cretáceo e Neógeno na Bacia do Amazonas, que migravam para oeste e leste, respectivamente

Fáceis litorâneas glaciais da formação Nhamundá (Siluriano inferior), na região de Presidente Figueiredo, AM, Bacia do Amazonas

CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superio

Uso de imagens multi-sensores na identificação de paleocanais do Rio Solimões nas regiões de Anori, Codajás e Beruri, Amazônia Ocidental

The paleochannels are important morphologic features that allow the understanding of drainage systems preterit and may help to understand the paleoenvironment changes. Aiming to corroborate the understanding of quaternary fluvial dynamics of River Solimões in the Anori, Codajás and Beruri regions (western Amazonia), the use data remote sensing, such as elevation images of SRTM (Shuttle Radar Topography Mission), SAR images (Synthetic Aperture Radar) / SIPAM (Sistema de Proteção da Amazônia), Geocover Landsat Mosaic 2000, and data from geology survey field, allowed the redefinition of three paleochannels features using visual interpretation techniques of satellite imagery, analyzing aspects such as texture, shape, size, pattern, geometry, color and tonality of images in areas with paleochannels. In the elevation images (SRTM), the SAR-SIPAM mosaic, and mosaic Geocover, the features of kilometer paleochannels are distinguished by morphology of elongated bars, with ridges and lower areas, which are truncate in various directions, defining a smoother texture in relation units adjacents terraces. The features paleochannels that show periods of avulsion and retaking sedimentation, inserted in deposits of fluvial terraces are indicative of the style fluvial meandering of the Solimões River at the time of its implementation, different of current style anastomosed observed in this section. The presence of significant paleochannels in alluvial deposits this portion of the western Amazonia, may be associated with the dynamic evolution of the Quaternary Purus Arch.Pages: 3611-361

Análise bitemporal do Rio Solimões no trecho entre Manacapuru e Manaus (Amazônia Central) por meio de imagens Landsat-5/TM

In this paper we present a study on the Solimões River between the cities of Manaus and Manacapuru, this area affected by erosion and deposition processes on the river. Some previous studies using remote sensing highlighted the presence of former presence of paleochannels with heterolytic inclined stratification, suggesting that this channel migrated in the past being a meandering river type, as opposed to the current standard stable channel featuring as anastomosed. In this study it was observed that the depositional processes formed small islands and new areas of accretion on the islands and marginal bars. The deposition is associated with decrease of flow velocity in the river water due to the enlargement of the channel, and hence induces the deposition of charge in suspension. In general, the erosion pattern the front areas of the islands and curvature of the channels, this erosion is popularly called "lands drooping". In this work, images Landsat-5/TM of 12/11/1991 and 29/11/2009 amounting to a period of 18 years, making it possible to observe large morphological changes in both river banks and islands. For this study we observed the predominance of depositional processes in relation to erosion, totaling approximately 60,965,847.83 and 51,645,646.19 ² m², respectively. This work may also provide sedimentological data associated with areas of erosion and deposition in the municipalities of Manacapuru and Iranduba, useful for urban planning and land use. Moreover, the generated map can help select appropriate areas for livestock and crops.Pages: 3627-363

New sedimentological and palynological data from surface Miocene strata in the central Amazonas Basin area

ABSTRACT The scarcity of stratigraphic data has hindered the demarcation of the outcropping area of Miocene deposits of the Amazon Basin, represented informally by the Novo Remanso Formation. Moreover, this unit is characterized by a sparse and irregular geographic distribution due to its sedimentological features and rare fossil content. Miocene deposits cropping out in central Amazonas Basin area were described in sedimentological terms and analyzed palynologically. All analyses were undertaken in samples collected at the Uatumã River banks (Itapiranga and São Sebastião do Uatumã cities). Lithostratigraphic data shows that Novo Remanso Formation consists of sandstones, with subordinate conglomerates and pelites, characteristic of a meandering fluvial paleosystem, with fluvial channel, point bar, floodplain and crevasse splay facies. The palynoflora retrieved from five samples consists exclusively of continental-origin palynomorphs dominated by angiosperms species. Trilete spores are well represented, while gymnosperms pollen grains are minor components. The presence of Psilastephanoporites tesseroporus, Syncolporites poricostatus, Jandufouria seamrogiformis and Polypodiaceoisporites potoniei ensure these deposits fits into the Grimsdalea magnaclavata palynozone (Regali et al. 1974a, b), and the Grimsdalea magnaclavata/Crassoretitriletes vanraadshooveni palynozones of Jaramillo et al. (2011) considered Middle Miocene age. This age is confirmed by the zonation of Jaramillo et al. (2011), based on the LADs of Bombacacidites baumfalki (11.57Ma) and Crototricolpites annemariae (12.91Ma); and the FAD of Psilastephanoporites tesseroporus (14.00Ma). With these new data presented herein, it is possible to assume that the Miocene strata represented by the Novo Remanso Formation covers a larger area in the basin than previously considered, and that it may be extended for about 300 km until the Manacapuru village, indicating a Miocene subsidence phase