Navegando por Assunto "Tocantins"

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O Dimensionamento das trajetórias tecnológicas de base agrária na Região Tocantina e suas implicações para o desenvolvimento local
(Universidade Federal do Pará, 2010-04-26) ROCHA, Enéas Nunes; COSTA, Francisco de Assis; http://lattes.cnpq.br/1820238947667908
The usual pattern of the rural capitalist development in Amazônia is based on the agricultural paradigm and on technologic employment paths, which are anchored to traditional institutions which reverts its favor to benefit of public politics for the rural segment expressed by the volume of credit accessed by these agents, while at the same time the usual pattern verified the existence of farming structures with a rationality opposite to those of the employer and with a different technological path, which participates with a representation of the rural production value, employing a larger volume of manpower and having a more efficient use of the resources at its disposal. The technological farming paths backed by the agro-forestry paradigm represented in the Tocantina Region as an alternative for sustainable development in the area and in this way, object and challenge the formation of public politics for the rural sector. So, development with social equity, ecological balance and economical efficiency in the Tocantina Region, would necessarily go through the incentives of technological procedures of farming and for changes in the institutional base that legalizes the current model.
Acesso aberto (Open Access)
Estudo sedimentológico da Formação Pimenteira (Devoniano) na borda sudoeste da bacia do Parnaíba (TO)
(Universidade Federal do Pará, 1998-04-15) SILVA, Valter Fernandes; CAPUTO, Mário Vicente; http://lattes.cnpq.br/1028384858323270
The part of the Pimenteira Formation studied occurs in the southwest portion of the Parnaíba Basin, in the region between the cities of Paraíso, Miranorte, Miracema, Tocantinea, Pedro Afonso and Itacajás in the State of Tocantins. This formation is considered to be deposited in a transgressive sea system tract of Middle and Late Devonian age (Givetian to Famenian). In the area on stage, the studies of the facies made it possible to individualize three associations of facies named here as A, B and C that were deposited on a shallow marine platform during transgressive sea level, regressive sea level and high sea level, respectively. These facies associations were interpreted as a product of the following depositional environments: 1) LAMMA MARINE PLATFORM (association of facies A) represented by F1 (laminated shale facies), Alp (sandstone with plane-parallel lamination and Aab (sandstone intercalated to claystones with sand pockets) where the deposition took place mainly from fine suspended sediments (pelites) intercalated with fine to very fine sandstones (psamites) deposited under the influence of oscillatory and tractive flow originated by waves; 2) PROXIMAL GLACIOMARINHO with SUBGLATIAL CHANNEL, associated (association of facies B), represented by facies Dmm (massive diamictite), Acf (sandstone with fluidized clast), F1 (laminated shale), Pgm (massive coarse paraconglomerate), Pfm (massive fine paraconglomerate) and Agm ( massive coarse sandstone), were deposited from glaciers, with associated subglacial channels, ice rafts and/or icebergs that displaced from the continent, floated in the sea, released generating melt water bringing a large amount of fine and coarse sediments, forming a plume loaded with suspended sediments in front of the gallery. With the decrease in energy, extensive layers of mud are deposited, with pebbles and gravels, dispersed, being released from ice rafts and/or icebergs, as they melt. The facies F1, Pgm, Pfm and Agm represent a bar deposit remaining from a subglacial channel. Subglacial channels discharge coarse sediments in front of the glacier that can be transported further by turbidity currents forming lenticular or layered deposits interspersed with diamictites; 3) SHALLOW MARINE PLATFORM UNDER THE ACTION OF STORMWAVES (association of facies C) represented by facies F-A1 (shale-laminated sandstone), F1-S (laminated shale interleaved with siltstones), Aco (sandstone with wavy cross bedding truncated by wave), Ap (sandstone with plane-parallel bedding), Apt (sandstone with plane-parallel and tabular cross bedding), Acot (sandstone with wavy truncated wave and tangential cross bedding), Ach (sandstone with hamocky cross bedding), Aptb (sandstone with plane-parallel and cross-tabular bioturbated bedding), Apmo (sandstone with plane-parallel bedding and wavy marks), Amg (massive sandstone with dispersed granules and pebbles) and Pm (massive paraconglomerate). The deposits are characteristic of platform bars with dominant hummocky structures, attesting to the action of storm waves, covered by extensive layers of marine shales deposited during the good weather phase. This facies association predominates in the upper portion of the Pimenteira Formation gradually passing to the deformed sandstones and diamictites of the Cabeças Formation east of the town of Pedro Afonso.
Acesso aberto (Open Access)
Fósseis de vegetais da Formação Pedra de Fogo:: aspectos taxonômicos, mineralogia e composição química
(Universidade Federal do Pará, 2000-08-11) MARTINS, Rosiney Araújo; COSTA, Marcondes Lima da; http://lattes.cnpq.br/1639498384851302; https://orcid.org/0000-0002-0134-0432
In the surroundings of Bielândia-TO, the Pedra de Fogo Formation (Upper Permian of the Parnaíba Basin) fossilized plants were collected, associated with a sedimentary succession, consisting of basal sandstone, overlaid by siltstones and claystone at the top, with nodules and levels flint continuums along its entire length. Morpho-anatomical studies, based on the identification of the type of vascular system (stele) preserved, of 17 specimens of fossilized plants revealed the presence of 9 stems, 4 roots and 2 petioles, and 2 specimens were not identified due to few anatomical elements. preserved. In general, the vascular system of the stems consists of masses of vascular bundles (xylem), limited by a reinforcing parenchyma wall, immersed in a fundamental parenchyma matrix. Traces of phloem were observed. Externally, it is surrounded by a layer of adventitious roots, constituted by vascular bundles immersed in fundamental parenchyma. This configuration is characteristic of the Psaroniaceae family, represented in this work by the genera Psaronius and Tietea, whose stele morphology allowed the identification of the species Psaronius brasiliensis and Tietea singularis. The roots exhibited a protostele-like stele and the petiole showed incipient structuring in the form of concentric rings. Only 1 specimen represented the Taxaceae family, due to the presence of sclereids and tracheids. Studies of 34 thin sheets, representative of transversal and longitudinal cuts to the preserved structure of the plant, showed the presence of granular and prismatic crystalline quartz, together with microcrystalline quartz, with emphasis on the chalcedony variety, both fibroradial and in fringes. In XRD, analyzes of 17 total samples and 17 isolated fractions of the identified tissues, the diffractograms drew the quartz pattern and small reflections of anatase, calcite and hematite. In the infrared spectra these samples recorded diagnostic bands of quartz (1166, 1082, 798, 800, 694, 511 and 462 cm-1) and strictly bands of organic matter (close to 3000 cm-1) and also the doublet 3700 and 3622 cm-1, along with bands 1103, 1035, 1011 and 915 cm-1 characteristic of disordered kaolinite. Quartz crystallinity is medium and low, with values close to 5.0 (calculated index, by XRD, according to Murata & Norman, 1976). SEM images reveal two distinct phases: one rich in microcavities, typical of parenchyma and parenchyma cell contacts, and another more massive, predominant in vessels and fundamental parenchyma. Electron microprobe analyzes show practically pure silica composition (99.73% SiO2) at values of 76.37% SiO2. The highest values of the main impurities were: Al2O3=5.95%; Fe2O3=2.45%; CaO=0.22%; Na2O=0.19 % and TiO2=1.52 % and are coincident with sclerenchyma samples, where kaolinite and hematite appear more frequently. The identified plants characterize a Permian flora, typical of swamps, where environmental changes, which made the pH more alkaline, promoted the death of the forest together with the permineralization of silica in the plant tissues, allowing the preservation of minute histological details. The presence of organic matter, related to methyl and methylene, also confirmed the origin of the process as infiltration and impregnation, developed at relatively low temperatures (below 200° C).
Acesso aberto (Open Access)
Geologia do perfil entre os municípios de Colina e Couto Magalhães no estado do Tocantins-Brasil
(Universidade Federal do Pará, 1997-02-18) MORAES JÚNIOR, Ofir; BORGES, Maurício da Silva; http://lattes.cnpq.br/1580207189205228; GÓES, Ana Maria; http://lattes.cnpq.br/2220793632946285
The area is part of the geological framework of the Tocantins Province, within the southernmost portion of the eastern Amazon. It is comprised between the parallels 08° 00' 00'' and 08° 30' 00'' and the meridians 48° 30' 00'' and 49° 30' 00''. The researched region encompasses a geological section that has insertion in the city of Colinas do Tocantins, continuing through the state highway TO-280 and ending in the vicinity of the city of Couto Magalhães/TO, making up about 107 km in profile. The chronostratigraphic division for the Baixo Araguaia Supergroup is adopted in this work, which includes, from base to top, the Estrondo and Pequizeiro groups. It was decided to include in the Estrondo Group the lithotypes attributed to the Xambioá Formation (in addition to the inclusion, in this group, of the Couto Magalhães Formation). This unit, in its eastern portion, is predominantly constituted by schists and quartzites, being more common biotite schists, feldspathic schists (gneissoids) and pure quartzites; in its western portion, outcrops the unit called, by some authors, the Couto Magalhães Formation, whose main lithology is represented by metasediments, predominantly phyllites. The Pequizeiro Group, in some works called the Pequizeiro Formation (included in the former Tocantins Group), is located in the central-west part of the area and requires rocks fundamentally formed by mica schists, with more frequent chlorite schists and interspersed biotite schists. The Parnaíba basin is represented at its western edge (eastern portion of the work area) by pelitic sediments from the Pimenteira Formation and sandstones from the Cabeças Formation. Essentially conglomeratic units attributed to the Rio das Barreiras Formation and to the Cipó Conglomerate unit were also observed, which, by some authors, have been considered as depositional variations of the Cabeças Formation, or the Piauí Formation or even the Pedra de Fogo Formation. These conglomerates are considered here to be of Eopaleozoic age. The sedimentological characteristics of the Rio das Barreiras Formation do not allow to correlate it with any unit of the Parnaíba basin; the Cipó Conglomerates may be related to the Serra Grande Formation of this basin. The structural features identified within the Baixo Araguaia Supergroup segregate not only two lithostratigraphic groups bundled in the Estrondo and Pequizeiro groups, but also two classes of structures: one originated by a purely ductile and non-coaxial tectonic system; and another coming from a predominantly brittle and coaxial tectonic, implanted later. They are marked by the constant presence of three most important types of tectogenous structures: [a] mylonitic foliation and schistosity; [b] stretch lineation; in addition to a third structure identified punctually; [c] compositional banding. Other not less important features are described as folds, crenulation cleavage, veins and lenses. Within the domain of brittle structures, failures of different types, joints or fractures are recognized, in addition to the lineament of various orientations that can represent different types of structures. The structures identified within the Parnaíba basin are fundamentally characterized through the action of processes originated by faults of a normal nature. They are structures originating from a fragile tectonic regime that generated important normal faults, both on a regional scale and on an outcrop scale. Of equal importance are the discontinuities described as joints that constitute striking impressions recorded in the two sedimentary units mapped within this portion of the basin. The correlation between the features displayed on the outcrop scale (faults, fractures, striations) with the regional scale lineaments shows the main direction according to a preferential north-south direction. This orientation can be visualized through the records (diagrams) of statistical treatments based on field measurements. The glaciotectonic structures studied refer to the deformed and chaotic geometries existing in the Devonian conglomeratic sand deposits belonging to the Cabeças Formation of the Parnaíba basin. They occur in much of the work area, along the easternmost portion of the region. They are mainly tillites that exhibit exuberant shear features, attributed to the tectonism of paleoglaciers at the end of the marine sedimentation of the Cabeças sandstones, in the Famenian. Deformed and slightly deformed tillites originated in a progressive deformation regime through tangential movements in simple and heterogeneous shear zones, generated in distal subglacial and glacial contact environments, are described. Two main relief compartments are exposed within the work area: [1] the one attributed to the Araguaia belt and [2] the one correlated to the sedimentary cover of the Parnaíba basin. Within the scope of the Araguaia belt, which is part of the Planalto do Interfluvio Araguaia-Tocantins, the following differentiated relief units were identified: [a] relief of aligned mountain ranges with sharp tops; [b] relief of hills with tabular tops; [c] relief of isolated hills with domed tops; [d] hilly relief with rounded tops; [and] tertiary plan; [f] fluvial plain of the Araguaia River; [g] Holocene alluvium. The last two sub-units are located in the Araguaia Depression. In the area belonging to the Parnaíba basin, included in the Depression of Tocantins, only two morphological units were identified; [h] relief of flat-topped hills; [i] relief of broad hills with flat and rounded tops. The evolution of the area in the context of the Araguaia belt is understood through the lithospheric distension-compression model, where the distensive phase promoted the formation of hemigraben dominated by normal faults inclined to the east; the compressive phase was characterized by the reactivation of normal thrust faults. The accommodation of these tensors took place through the formation of an imbricated system with associated nappes. The Baixo Araguaia Supergroup has transgressive marine sequence characteristics. The installation of the Parnaíba basin occurred through a NW-SE extension axis during the early Paleozoic, in the Ordoviciian-Silurian. The effects of this opening led to the formation of extensional faults that were concentrated on the W, E and SE edges that were controlled by ancient Precambrian lineaments. The clastic deposits of the Canindé Group, records of the Devonian of the basin, represent the alternation of regressive cycles (pelites of the Pimenteira and Longá formations) and transgressive (sandstones of the Itaim and Cabeças formations) and are characterized by deposition in temperate to cold climates near glaciers.
Acesso aberto (Open Access)
Os Fundamentos agrários do desenvolvimento da Região Tocantina
(Universidade Federal do Pará, 2005) ROCHA, Enéas Nunes; COSTA, Francisco de Assis; http://lattes.cnpq.br/1820238947667908
The agrarian foundations of the development of the Tocantina Region are related to the form of occupation of the soil and as the regional several productive structures of the agrarian are articulated. The strategy of official economic intervention in the Tocantina Region privileged the great enterprises agroindustriais through financial and monetary incentives, generating, besides all, serious environmental problems, agrarian conflicts and desregionalization of the property of the money. The base of these productive structures is the property landowner, the salaried work of low qualification and the homogeneous production. The process of characterized development, then, for the exploration of the natural resources and for the monoculture, was not take in considerated other important aspects of the local development, the formation of human and social goods of the area and consequently they were not capable to improve the conditions of life of the population. As alternative to the concentrated and excludent model, are the rural structures, that using small units of land, family work, diversified production and capacity dealing with the natural resources in order not it to drive the lackness, they act in such a way that its efficiency is determined by the capacity of work of each family, its intern rationality defines, then, a way of performance, with high productivity in the Tocantina Region, being able to contribute with the employment growth and income, as well as with the development.
Acesso aberto (Open Access)
A zona zeolítica da Formação Corda, Bacia do Parnaíba
(Universidade Federal do Pará, 2002-02-14) REZENDE, Nélio das Graças de Andrade da Mata; COSTA, Marcondes Lima da; http://lattes.cnpq.br/1639498384851302; https://orcid.org/0000-0002-0134-0432
Since the occurrence of zeolites in the Parnaíba Basin were revealed, in the middle of the last decade, several works have been published addressing the main traces of geological conditioning, as well as the possibility of processing the ore. These investigations provided an overview of the mineralogical composition of the deposit and identified the presence of zeolites stilbite and laumontite occurring as cement in fluvial and eolian sandstones of the Corda Formation, associated with caucite and smectites. They also provided some data on the chemistry of the whole rock and one of the zeolite species (stilbite). They did not contain information about paragenesis and the hypotheses raised about genetic aspects were inconsistent. There was speculation about the possibility of a hydrothermal influence and the probable existence of a well-defined mineralogical zoning, which could favor eventual exploratory investments. The main objective of this dissertation was to systematically study two representative sections of the Zeolite Zone of the Corda Formation, to define the paragenesis and the spatial pattern of mineralogical distribution, as well as to elucidate the issue of genetic modeling for the accumulation of zeolites. Additionally, we tried to open perspectives for possible fields of application of this material. The work methodology involved an intensive bibliographic research on the geological conditioning of zeolite deposits in sedimentary rocks and on the physicochemical parameters that regulate the stability of stilbite and laumontite. This theoretical foundation was an important subsidy in the interpretation of the data obtained through various analytical resources, managing to assemble a table that provides a generic overview of the diagenetic environment of the Corda Formation, and its evolution, with emphasis on the conditions of pressure, temperature and chemistry of the zeolite zone, and the spatial distribution of the two zeolites, in addition to paragenesis relationships. The study of the isotopic compositions of carbon and oxygen was an important auxiliary tool in this interpretation The focus on Regional Geology admits the need for a review of the Mesozoic stratigraphic order of the basin, with the possibility of dissociating the Corda Formation into two distinct segments, and emphasizes the importance of the role played by basic volcanic rocks in this order, and their spatial and genetic link with zeolites. The local geological context reflects a broad sedimentary system, predominantly eolic and fluvial, developed over basaltic flows. Mineralogically, two distinct universes can be highlighted: a) a detrital one, containing grains of diverse composition in which quartz predominates and, subordinately, basalt fragments, in addition to feldspars, quartzite, chert and limestone, among others; b) an authigenic phase, with the paragenesis involving a ferruginous coating, the smectites (predominantly montmorillonites), and zeolites (stilbite and laumontite) and calcite. It is not possible to define the order of crystallization of zeolites among themselves, nor of these with calcite, as there is evidence that these minerals are cogenetic and formed from fluctuations in the chemical balance of the interstitial fluid, both in fluvial and aeolian facies. The texture of the sandstone, characterized by a predominantly floating and/or punctual packing, the isotopic composition of oxygen and carbon in the calcitic cement and the absence of albitization in the detrital plagioclase, in addition to the degree of preservation of the smectites and the absence of siliceous cement, provided subsidies to characterize a diagenesis dominated by temperature and pressure conditions compatible with surface conditions, with the zeolite process involving an open hydrological regime, developed in an arid and semi-arid environment. Adsorption tests for copper show that phases enriched in laumontite have a relatively high performance, compatible with some activated aluminas, which recommends carrying out more complete investigations of the industrial properties of the zeolite ore from the Corda Formation.