UNIVERSIDADE FEDERAL DE GOIÁS PRÓ-REITORIA DE PESQUISA E PÓS-GRADUAÇÃO PROGRAMA DE DOUTORADO EM CIÊNCIAS AMBIENTAIS Área de concentração: Estrutura e Dinâmica Ambiental CONTROLES FÍSICOS NA EVOLUÇÃO DAS UNIDADES GEOAMBIENTAIS DA BACIA DO RIO ARAGUAIA, BRASIL CENTRAL Cidney Rodrigues Valente GOIÂNIA - BRASIL MAIO/2007 ii CIDNEY RODRIGUES VALENTE ORIENTADOR: PROF. DR. EDGARDO M. LATRUBESSE CONTROLES FÍSICOS NA EVOLUÇÃO DAS UNIDADES GEOAMBIENTAIS DA BACIA DO RIO ARAGUAIA, BRASIL CENTRAL GOIÂNIA - BRASIL 2007 Tese submetida ao Programa de Doutorado em Ciências Ambientais da Universidade Federal de Goiás, como um dos requisitos para a obtenção do título de Doutor em Ciências Ambientais. iii iv A minha esposa Telma e aos meus filhos Nathalye, Leandro e Guilherme que estiveram sempre ao meu lado, ajudando na minha construção pessoal e profissional. Aos meus pais Joaquim de Abreu Valente e Délia Rodrigues Valente que são meu orgulho e um exemplo de afeição e amor. Aos meus irmãos Joélia, Alair, Josino, Augusto, Alcione, Joir, Hélia e Nélia que no ambiente familiar nós aprendemos desenvolver a união, a compreensão e o companheirismo. . v AGRADECIMENTOS Primeiro, agradeço a Deus por esta nova realização em minha vida, porque Ele é a fonte de tudo que tenho, de tudo que sou e o que eu posso vir a ser. Agradeço ao Serviço Geológico do Brasil (CPRM) pelo apoio financeiro e institucional que permitiu o desenvolvimento desta pesquisa. Gostaria de agradecer a CABAH-Rede XII-k CNPq-CYTED Controles Abióticos de la Vegetación en Áreas Húmedas pelo suporte financeiro para a datação radiométrica de amostras pelo método de OSL (Optically Stimulated Luminescence). Este estudo foi beneficiado pelo Impacts of Land-Use Change on Water Resources in the Brazilian Cerrado (LULCC) supported by NASA-USA, Earth Science Enterprises, 2700-0087. Sou grato à Universidade Federal de Goiás (UFG), em particular aos professores do Programa de Doutorado em Ciências Ambientais (CIAMB). Agradeço ao Instituto Brasileiro do Meio Ambiente e dos Recursos Naturais Renováveis (IBAMA). Em especial às agências de São Miguel do Araguaia e Palmas, respectivamente, em nome de Weber Rodrigues Alves e Ana Carolina Silva pelo apoio logístico de campo ao longo dos rios Araguaia e Javaés e no Parque Nacional do Araguaia. Eu também agradeço a Agência Ambiental do Estado de Tocantins pelo apoio durante o trabalho de campo na região da Lagoa da Confusão. Sou grato ao Prof. Dr. Edgardo M. Latrubesse (Universidade Federal de Goiás e Universidad Nacional de La Plata, Argentina) pela amizade, estímulo e orientação que me conduziu por uma vida científica e acadêmica extremamente rica. Sou particularmente agradecido aos geólogos Inácio M. Delgado (CPRM) e Dr. Augusto José Pedreira (CPRM) pela leitura crítica do manuscrito referente a geologia. Expresso meu agradecimento e gratidão ao Dr. Laerte G. Ferreira (Universidade Federal de Goiás) pela leitura e sugestão do manuscrito referente ao artigo de vegetação. Sou agradecido ao Dr. Enrique Francês Arriola (Universidad de Cantabria, España) pelas sugestões quando da realização do exame geral de qualificação desta tese. Em particular, gostaria de agradecer a Profa. Gisele Dionísio da Silva pela revisão do inglês dos manuscritos e pela sua amizade. Agradeço a Raimundo Rodrigues Barbosa pela sua ajuda durante os trabalhos de campo e José Alencar pela vi amizade e incentivo. Esta tese é oferecida in memorian ao Dr. Paulo Veneziani, ao geólogo Hermes Inda e ao amigo Vicente Brandão. vii ÍNDICE AGRADECIMENTOS...……………………………………………................... v RESUMO.............................................................................................................. 1 ABSTRACT …………………………………………………………………..... 3 INTRODUÇÃO GERAL...................................................................................... 5 CONCLUSÕES…………………………………………………………............. 10 REFERÊNCIAS…................................................................................................ 13 PAPER I ………………….....…………..…....................................................... 14 GEOLOGY AND REGIONAL GEOMORPHOLOGY OF THE ARAGUAIA RIVER BASIN, CENTRAL BRAZIL: PART I – GEOLOGY PAPER II ………………………………………………………………………. 57 GEOLOGY AND REGIONAL GEOMORPHOLOGY OF THE ARAGUAIA RIVER BASIN, CENTRAL BRAZIL: PART II – GEOMORPHOLOGY PAPER III ………………….………………………………………………….. 89 PALEOHYDROLOGICAL CHARACTERISTICS AND RIVER CHANNEL AVULSIONS DURING THE MIDDLE AND UPPER PLENIGLACIAL IN BANANAL BASIN, BRAZIL PAPER IV............................................................................................................ 123 RELATIONSHIPS AMONG VEGETATION, GEOMORPHOLOGY AND HYDROLOGY IN THE TROPICAL WETLAND SAVANNA REGION OF CENTRAL BRAZIL: THE BANANAL ISLAND 1 RESUMO A bacia hidrográfica do Araguaia, situada no Brasil Central, drena uma área de aproximadamente 384.600 km² onde a cobertura de vegetação está representada por dois biomas brasileiros: o Cerrado e fragmentos do Amazonas. Esta região revela uma grande diversidade de ambientes biológicos, geológicos e geomorfológicos. O objetivo geral desta pesquisa é fornecer uma revisão completa das Províncias Geológicas da bacia do Araguaia como suporte para a cartografia geomorfológica. Os objetivos específicos, em escalas local e regional, consistiram em: (i) definir a evolução tectono-geolólogica; (ii) datações radiométricas pelos métodos OSL (Optically Stimulated Luminescence), TL (Thermoluminescence) e 14C (Radiocarbono) em sedimentos da Bacia Bananal; (iii) avaliar os controles das unidades morfo- vegetacionais do bioma Cerrado na planície da Ilha do Bananal. Imagens digitais de sensoriamento remoto do SRTM (Shuttle Radar Topography Mission), MODIS (Moderate Resolution Imaging Spectroradiometer), ETM+ (Enhanced Thematic Mapper Plus) e dados aerogeofísicos foram processados no ENVI (Environment for Visualizing Images). Estes produtos de sensoriamento remoto foram interpretados, compatibilizados com dados de campo e integradas no ambiente GIS (Geographic Information System). Seis Províncias Estruturais com padrões tectônicos e idades distintas foram identificadas: Tocantins, Carajás, Amazônia Central, Paraná, Parnaíba e Parecis. As principais Províncias e Unidades Geológicas regionais estão representadas por: terrenos arqueanos do Maciço de Goiás e do Domínio Rio Maria (terrenos TTG e greenstone belts). O Paleoproterozóico consiste de rochas dos domínios Iriri-Xingu e Porto Nacional-Nova Crixás. O Neoproterozóico está representada pelo Arco Magmático de Goiás e as faixas dobradas dos cinturões Araguaia e Paraguai. As bacias sedimentares Paleozóico-Mesozóicas do Paraná, Parnaíba e Parecis e a bacia fluvial Quaternária do Bananal constituem as mais importantes bacias intracratônicas da área do estudo. Reativações tectônicas generalizadas, principalmente de movimento de soerguimento durante o Cenozóico, favoreceram os processos de denudação com a 2 geração de três Superfícies de Aplainamento Regional (RPSs). Estas superfícies de erosão estão escalonadas em diferentes altitudes em relação ao nível do mar, denominadas de RPSII (1000-750m), RPSIII (750-550m) e RPSIV (550-180m). Os processos denudacionais causaram a deposição da bacia intracratônica do Bananal, que representa o grande sistema de agradação Quaternária do Brasil Central, com área de aproximadamente 106.000 km². Internamente, esta bacia possui diversas unidades morfo-sedimentares depositadas durante o Pleistoceno Médio (240.000±29.000 a 159.600±18.542 anos) ao Pleistoceno Superior (121.000±15.000 a 17.200±2.300 anos) e durante o Holoceno (9.800±1.100 anos até o presente), quando ocorreram significativas mudanças paleohidrológicas e paleoclimáticas. Os registros sedimentares em associação com as datações radiométricas (OSL e TL) obtidas em sedimentos fluvial da Formação Araguaia mostraram que a Bacia Bananal esteve dominada por avulsões de rios em dois períodos distintos: durante o Pleniglacial Médio (56.600±5.9000 a 34.000±4.600 anos) e no Pleniglacial Superior (26.400±3.100 a 17.200±2.300 anos). As reativações neotectônicas de falhas antigas (Pré-Cambrianas) que ocorrem associadas à Zona Sismogênica Goiás-Tocantins constituem os principais fatores que geraram avulsões de drenagem, paleocanais (canais abandonados), incisões de rios e a arquitetura sedimentar da Formação Araguaia durante o Pleistoceno Médio e Superior (240.000±29.000 a 17.200±2.300 anos). A integração de dados multidisciplinares (vegetação, hidrologia, geomorfologia e geologia) indica que o crescimento e a distribuição espacial das fitofisionomias do bioma Cerrado estão controlados principalmente pelas pequenas variações altimétricas do relevo, com a influência da precipitação anual e prolongada inundação sazonal entre janeiro e maio. As áreas pobremente drenadas e encharcadas nesse período favoreceram o crescimento de tipos de vegetação mais tolerantes à inundação, como as fisionomias mais herbáceas do bioma Cerrado (Campo Limpo e Campo Cerrado), enquanto as inundações por longo tempo inibem o crescimento dos tipos fisionômicos mais densos (Cerradão e Cerrado stricto sensu). Portanto, na Planície do Bananal existe uma 3 relação entre unidades de vegetação com determinados tipos geomorfológicos (unidades morfo-vegetacionais). ABSTRACT The Araguaia River Basin, located in Central Brazil, drains an area of approximately 384,600km² where the vegetation cover is represented by two Brazilian biomes: the Cerrado and fragments of the Amazon. This region reveals a rich biodiversity and great geodiversity of geological and geomorphologic environments. The aim of this research in large-scale is to provide a thorough review of the geological provinces as a support for the geomorphologic cartography. In local and regional scales, the objectives consisted of defining the tectono-geological evolution, radiometric dating in fluvial sediments of river channels (abandoned and active) from the Quaternary Bananal Basin, and of assessing the morphovegetational controls of the Cerrado biome in the Bananal Island floodplain. Remote sensing images from SRTM (Shuttle Radar Topography Mission), MODIS (Moderate Resolution Imaging Spectroradiometer), ETM+ (Enhanced Thematic Mapper Plus), and aerogeophysical data were processed in ENVI (Environment for Visualizing Images) software, interpreted and compared with fieldwork data and integrated in GIS (Geographic Information System) environment for the geomorphologic mapping, and compatibilized with previous geological information. Six Structural Provinces with different tectonic patterns and distinctive ages were identified: Tocantins, Carajás, Central Amazônia, Paraná, Parnaíba, and Parecis. The main regional Geological Provinces and Geological Units are represented by Goiás Massif and Rio Maria Archean domains (TTG terrains and greenstone belts). The Paleoproterozoic consists of Iriri-Xingu and Porto Nacional-Nova Crixás domains. The Goiás Magmatic Arc and Araguaia and Paraguay belts represent the Neoproterozoic. The Paleozoic-Mesozoic sedimentary basins (Paraná, Parnaíba, and Parecis) and the Quaternary sedimentary basin (Bananal) constitute in large scale the main intracratonic basins of the study area. Generalized tectonic reactivations mainly of uplift movements on Precambrian basement rocks and Paleozoic/Mesozoic sedimentary basin rocks during the Cenozoic 4 favored the denudation processes with generation of three Regional Planation Surfaces (RPSs), scheduled in different altitudes: RPSII (1000-750m), RPSIII (750-550m), and RPSIV (550-180m above sea level). As a result, these erosive processes caused the deposition of the intracratonic Bananal Basin, which represents the great aggradation system with approximately 110,000km². Internally, this basin contains several morphosedimentary units deposited in the Quaternary and during the Holocene when significant paleohydrological and paleoclimatic changes occurred. Sedimentary registers in association with radiometric dating by OSL (Optically Stimulated Luminescence) and TL (Thermoluminescence) in fluvial sediments from Araguaia Formation showed that the Bananal Basin was dominated by river avulsions in two distinct periods: during the Middle Pleniglacial (56,6±5,9 to 34,0±4,6 ka BP) and in the Upper Pleniglacial (26,4±3,1 to 17,2±2,3 ka BP). Neotectonic reactivations from old faults of the Precambrian basements which occur in association with the GTSZ (Goiás-Tocantins Seismogenic Zone) constitute the main factors that generated drainage avulsions, paleochannels (abandoned channels), and incision of rivers as well as landforms and sedimentary architecture of the Araguaia Formation during the Middle and Upper Pleistocene (240±29 to 17,2±2,3 ka BP). The integration of multidisciplinary data (vegetation, hydrology, geomorphology, and geology) indicates that the growth and the spatial distribution of the phytophysiognomies of the Cerrado biome are controlled mainly by the small altimetric variations of the geomorphologic forms, with an influence of the annual rainfall and prolonged seasonal flooding between January and May. Poorly drained and soaked areas during a longer period favored the growth of more flood-tolerant vegetation such as the herbaceous physiognomies (Cerrado grassland and shrub Cerrado) and inhibited the growth of denser physiognomic types such as the woody plants (e.g. wooded Cerrado and Cerrado woodland). However, in the Bananal Plain exists a relationship between vegetation units with determined geomorphologic units (morphovegetational units). 5 INTRODUÇÃO GERAL Esta pesquisa está inserida no Programa de Doutorado em Ciências Ambientais (CIAMB) da Universidade Federal de Goiás (UFG), na área da concentração de Estrutura e Dinâmica Ambiental. Entre muitas ações possíveis podem ser enfatizados o monitoramento e a análise de recursos naturais da geodiversidade e biodiversidade. Este programa tem como uma de suas bases o estudo científico a fim de subsidiar ações de políticas públicas e pesquisa ambiental de naturezas multidisciplinar e interdisciplinar da própria universidade, com ênfase aos aspectos físicos e bióticos do bioma Cerrado, conservação e gerenciamento da biodiversidade. O Brasil, pais de dimensão continental, com aproximadamente 8.514.877 km², contem uma rica biodiversidade distribuída em seis biomas: Floresta Amazônica, Cerrado, Caatinga, Floresta Atlântica, Pantanal e Pampa. Estes biomas apresentam variações em termos de altitude, latitude, clima e geoambiente. Neste contexto, a bacia hidrográfica Tocantins-Araguaia tem uma área de cerca de 800.000 km² e uma descarga média anual de aproximadamente 12.000 m³s-1 (Latrubesse, 2003). Os rios deste sistema são os principais contribuintes de água doce que drenam a área do Cerrado. O bioma Cerrado é representado por formações de vegetação bastante complexas que mostram uma variação de fisionomias e composição florísticas, com cerca de 1.5% de plantas endêmicas, considerado como um dos 25 hotspots da Terra para a conservação da biodiversidade (Mittermeier et al., 1998; Myers et al., 2000). As áreas objeto deste estudo compreendem quatro regiões: (i) toda a bacia hidrográfica do Araguaia; (ii) o médio e alto Bacia do Araguaia; (iii) a bacia sedimentar do Bananal e (iv) a Ilha do Bananal. A bacia do rio de Araguaia, localizada na região central do Brasil, possui uma área de aproximadamente 384.600 km². Esta bacia é usualmente dividida em três segmentos: Alto, Médio e Baixo rio Araguaia. Nesta área é apresento o estado da arte da geologia através de uma revisão dos trabalhos pré-existentes da geotectônica e geologia com algumas modificações, além da evolução tectono-geológica da área de 6 estudo. A área da bacia do rio Araguaia está representada por seis Províncias Estruturais: Tocantins, Carajás, Amazônia Central, Paraná, Parecis e Parnaíba. As unidades geológicas destas províncias são caracterizadas por uma grande variedade litológica, metamorfismo e deformação gerados desde o Arqueano ao Holoceno e foram desenvolvidas em diversos paleoambientes (marinho, fluvial, lacustrino, desértico e vulcanogênico). A infracrosta Pré-Cambriana consiste de várias Províncias Geológicas (Maciço de Goiás; domínios Rio Maria, Iriri-Xingu e Porto Nacional-Nova Crixás; Arco Magmático de Goiás e os cinturões Araguaia e Paraguai). As rochas supracrustais estão representadas por três bacias sedimentares Paleozóico-Mesozóicas (Paraná, Parnaíba e Parecis) e uma bacia sedimentar Quaternária bem desenvolvida situada na região do médio rio Araguaia, denominada de Bacia Bananal, com aproximadamente 106.000 km². Na porção norte desta bacia sedimentar ocorre a Ilha do Bananal, com uma área de 20.000 km², que é sazonalmente inundada, considerada por diversos autores como a maior ilha fluvial do mundo. Os processos de denudação e agradação do alto e médio Araguaia que atuaram durante o Quaternário geraram três Superfícies de Aplainamento Regional e um complexo mosaico de unidades morfo-sedimentares associado à Bacia Bananal. A planície desta bacia é inundada temporariamente, durante a estação chuvosa, por precipitação de águas locais e por saturação do nível freático, que pode ser classificada como seasonal wetland. A Bacia Bananal é uma das mais importantes bacias sedimentares intracratônicas do Quaternário da América do Sul e preserva um bom registro de condições paleohidrológicas. A importância ecológica desta planície fluvial quanto à biota, aos sistemas lacustrinos e os cinturões das planícies fluviais têm chamado à atenção de pesquisadores nesta última década pela sua diversidade e fragilidade. Estes estudos sistemáticos abordaram as variações morfológicas do canal do rio Araguaia, visando quantificar o balanço de erosão/assoreamento do sistema fluvial, com a finalidade de oferecer subsídio científico aos estudos de planejamento ambiental. Pouco se sabe sobre as interações que controlam a dinâmica paleohidrológica e morfo-sedimentares das planícies fluviais e aluviais durante o Quaternário, bem como 7 os controles abióticos (geologia, geomorfologia e inundações periódicas por longo tempo) na distribuição espacial das unidades de vegetação do bioma Cerrado. Os registros sedimentares fluviais da Bacia Bananal podem ser usados como indicadores de mudanças paleoclimáticas e paleohidrológicas que ocorreram no Pleistoceno. Durante os processos sedimentológicos e geomorfológicos, as avulsões foram os principais mecanismos que atuaram no Pleniglacial Médio e Superior, incluindo o Último Máximo Glacial (UMG). Conseqüentemente, as datações radiométricas pelos métodos de TL (Termoluminescence) e OSL (Optically Stimulated Luminescence), realizadas nos sedimentos arenosos da Bacia Bananal, nesta pesquisa, foram importantes porque estes registros constituem as primeiras idades obtidas em grande sistema fluvial tropical do território brasileiro. Este estudo tem como objetivo geral uma revisão da geotectônica da área da bacia do rio Araguaia. Os objetivos específicos foram: (i) definir os diferentes movimentos tectônicos e a evolução tectono-geológica da área da bacia hidrográfica do Araguaia; (ii) cartografia das unidades geomorfológicas que compõem os sistemas denaducional e agradacional da área da bacia hidrográfica do alto e médio Araguaia; (iii) caracterizar os ambientes paleohidrológicos e os processos que controlam as avulsões de canais dos rios, datando os eventos usando técnicas de datação absolutas (TL e OSL) nos sedimentos da Bacia Bananal; (iv) introduzir a área da Bacia Bananal no contexto paleoambiental tropical da América do Sul; (v) delimitar a distribuição espacial das unidades da vegetação e os controles das unidades morfo-vegetacionais da Ilha do Bananal. Esta pesquisa foi desenvolvida usando a análise e interpretação de imagens de sensoriamento remoto, tais como: SRTM (Shuttle Radar Topography Mission), MODIS (Moderate Resolution Imaging Spectroradiometer), ETM+ (Enhanced Thematic Mapper Plus) e dados aerogeofísicos do PGBC (Projeto Geofísico Brasil- Canadá). A interpretação visual foi complementada com atividades de processamento digital de imagens através do software ENVI (Environment for Visualizing Images) e a integração dos dados foram realizados utilizando um GIS (ArcMap). A extração das feições topográficas e padrões morfológicos de relevo foram identificados em imagem de relevo sombreado, com diferentes geometrias de 8 iluminação, através de um Modelo de Elevação Digital obtida de imagens SRTM. Estes dados foram integrados com imagens ETM+ do satélite Landsat da estação seca de julho e setembro de 2000. O mapeamento de tipos fisionômicos do Cerrado, na Ilha do Bananal, foi realizado através de imagens MODIS, do mês de setembro de 2003 (estação seca), utilizando o algoritmo de classificação digital pelo método de Paralelepípedo. A série temporal de imagens MODIS-VI foi adquirida a partir de MOD13Q1 (250m). Cinco recomposições bi-mensal da Ilha do Bananal foram filtradas com base nos meta dados NDVI (QA), para o período de março a outubro de 2003. Para a coluna geológica foi utilizada a seqüência cronológica do ICS (International Commission on Stratigraphy), publicada em 2006, e ratificado pelo IUGS (International Union of Geological Sciences). Três determinações pelo método de Radiocarbono (14C) obtidas em amostras de matéria orgânica (madeira e folha) foram realizadas no Radiocarbon Dating Laboratory at University of Waikato, Hamilton, New Zealand. Enquanto quinze amostras de areia de canais de rios abandonados e de barrancos do rio Araguaia foram datadas pelos métodos de OSL e TL no Laboratório de Vidro e Datação da Faculdade de Tecnologia de São Paulo, Brasil. O trabalho de campo foi realizado em duas etapas durante a estação seca, entre agosto e setembro 2005 e 2006. O estudo foi desenvolvido através de perfis em rodovias e em barco no rio Araguaia. Nesses períodos, foram executadas escavações de trincheiras, furos de trado, descrições de perfis nos barrancos de rios e amostragem de sedimentos para datação pelos métodos de 14C, TL e OSL. A classificação das fisionomias do Cerrado, medidas de fraturas e falhas, bem como informações geológicas e geomorfológicas foram analisadas e estudadas no campo. Esta tese foi organizada na forma de quatro papers científicos: O paper I é intitulado “Geology and regional geomorphology of the Araguaia River Basin, Central Brazil: Part I - Geology” e será submetido ao Journal of South American Earth Sciences. Este artigo constitui o estado da arte da geologia da área da bacia hidrográfica do rio Araguaia e apresenta uma revisão completa dos estudos precedentes de geologia, geotectônica e dos principais recursos minerais desta região. 9 Também é discutida a evolução tectono-geológica e as evidências dos eventos neotectônicos que ativaram falhas Pré-Cambrianas e que persistem até o presente. O paper II é intitulado “Geology and regional geomorphology of the Araguaia River Basin, Central Brazil: Part II - Geomorphology” e será submetido ao Journal of South American Earth Sciences. Este artigo apresenta uma evolução metodológica da cartografia geomorfológica do território Brasileiro. Contempla os grandes sistemas geomorfológicos, isto é, os Sistemas denudacional e Agradacional, cujas evoluções são essencialmente genéticas e dinâmicas. No Sistema Denudacional as Superfícies de Aplainamentos Regionais (RPSs) são individualizadas e escalonadas em diferentes altitudes. Cada RPS pode conter duas ou mais subdivisões, com variados graus de dissecações (muito fortes, forte, médio, baixo e muito baixo), bem como as feições residuais resistentes à erosão (morros e colinas, estruturas dobradas, hogbacks, inselbergs, etc.). Entre duas RPSs geralmente ocorre uma Zona de Erosão Recuante. O paper III, intitulado “Paleohydrological characteristics and river channel avulsions during the Middle and Upper Pleniglacial in the Bananal Basin, Brazil” foi submetido a Quaternary Science Reviews. Esta pesquisa estuda as avulsões de rios associadas às atividades neotectônicas e mudanças paleoclimáticas que ocorreram na bacia sedimentar do Bananal durante o Pleistoceno Médio e Superior. As datações radiométricas foram obtidas em amostras da areia através dos métodos OSL e TL. As idades de 14C foram obtidas em amostras de matéria orgânica de estratos de barrancos do rio Araguaia. O paper IV é intitulado “Relationships between vegetation, geomorphology, and hydrology in the tropical wetland region of Central Brazil: the Bananal Island”. Este artigo tem um caráter multidisciplinar e interdisciplinar e apresenta os relacionamentos entre as variáveis físicas que controlam a distribuição espacial dos tipos fisionômicos do bioma Cerrado na Ilha do Bananal. O uso de uma série temporal de imagens MODIS-VI e Landsat ETM+ suportados por dados de campo permitiram o mapeamento da distribuição espacial das fitofisonomias do Cerrado e a relação entre as unidades geomorfológicas e as unidades de vegetação. 10 CONCLUSÕES A bacia hidrográfica do Araguaia, com uma área aproximada de 384.000 km², ocupa uma região de transição entre os biomas Cerrado e Amazônico, na região central do Brasil. Esta bacia apresenta evolução geológica, geomorfológica, paleohidrológica e morfo-vegetacional bastante complexa cujos processos ocorreram através de períodos geológicos de grande escala até os presentes dias. Nesse contexto, a infracrosta Pré-Cambriana reflete histórias policíclicas do tectonismo e metamorfismo do seu embasamento na região de estudo. Os terrenos mais antigos consistem de rochas com idade e composição muito diversificadas, tais como os terrenos Arqueanos TTG e greenstone belts (~3.0-2.7 Ga); ortognaisses Paleoproterozóicos e seqüências vulcano-sedimentares (~2.2-2.0 Ga); cinturões dobrados metamórficos e arcos magmáticos Neoproterozóicos (~900-600 Ma). O domínio supracrustal contém várias e extensivas bacias sedimentares intracratônicas geradas no Paleozóico e Mesozóico (Paraná, Parnaíba e Parecis), bem como a bacia Quaternária do Bananal depositada durante o Pleistoceno Médio e Inferior (~240.000 a 17.000 anos). Tanto as rochas da infracrosta como a supracrosta foram geradas em distintos paleoambientes (marinho, fluvial, lacustrino e desértico). Em particular, as rochas do embasamento foram afetadas por três eventos tectono- metamórficos do Pré-cambriano: Ciclo Jequié (~2.7 Ga), Ciclo Transamazônico (~2.0 Ga) e Ciclo Brasiliano (900-520 Ma). O ciclo orogenético Brasiliano, o mais expressivo na região, é caracterizado por orogenia relacionada a colisões associados à falhas de empurrão de baixo ângulo (Faixas Araguaia e Paraguai) e um expressivo sistema de falhas transcorrestes com direção N20-40E de alto ângulo, denominado de Lineamento Transbrasiliano. Reativações tectônicas que atuaram nestes sistemas de falhas Pré-Cambrianas durante o Cenozóico se estenderam até o Neogeno. Essas atividades tectônicas podem ter sido o verdadeiro gatilho geomorfológico que favoreceram os processos de erosão e desenvolvimento de três unidades denudacionais, denominadas de Superfícies de Aplainamento Regional (RPSII, RPSIII e RPSIV) e Zonas de Erosão Recuantes. Associados às RPSs ocorrem estruturas dobradas, hogbacks, inselbergs, morros e 11 colinas que representam remanescentes do embasamento resistentes à erosão, tais como: granitos, quartzitos, calcários, etc. Estas superfícies estão escalonadas em diferentes altitudes, com quotas que variam entre 1000 e 750 m (RPSII), 850 e 550 m (RPSIII) e 550 e 165 m (RPSIV). O sistema agradacional, representado pela Bacia Bananal, é constituído por um complexo mosaico de unidades morfo-sedimentares que inclui as planícies fluviais e aluviais atribuídas ao Pleistoceno Médio e Superior (Formação Araguaia) e Holoceno (depósitos aluviais). As unidades geomorfológicas mais representativas deste sistema são constituídas por: (i) Planície Fluvial Ligeiramente Dissecada; (ii) Planície Fluvial com Scrolls de Meandro; (iii) Planície Fluvial com Padrão Meandrante; (iv) Cinturão Fluvial Abandonado; (v) Cinturão Fluvial Abandonado com Rio de Meandros Subadaptados (Underfit Rivers). O alagamento na Planície Bananal é independente do transbordamento das grandes cheias do rio Araguaia. A inundação é resultado de três fatores: (i) alta precipitação entre janeiro e março; (ii) cobertura superficial da planície com predominância de solo argiloso (baixa permeabilidade); (iii) relevo muito plano com baixa altitude (baixo estrutural) que funciona como uma extensiva planície de acumulação de água tanto superficial como subterrânea. As características litológicas, estruturais e hidrológicas conferem a Bacia Bananal, mais especificamente a Ilha do Bananal, o modelo de um grande reservatório de águas subterrâneas. Mudanças tectônicas e climáticas que ocorreram desde o Ultimo Interglacial influenciaram na evolução da presente paisagem da Planície Bananal. O processo de sedimentação da Formação Araguaia foi importante durante o Pleistoceno Médio e Superior, entre 240.000±29.000 e 17.200±2.300 anos. Nesse contexto, idades OSL e TL obtidas em areias de canais abandonados de rios permitiram a interpretação de que as avulsões dos rios na Planície Bananal foram mais intensivas durante o Pleniglacial Médio ou estágio isotópico 3, entre 56.600±5.900 e 34.000±4.600 anos. Este processo avulsivo prolongou até o Pleniglacial Superior ou estágio isotópico 2, entre 26.400±3.100 e 17.200±2.300 anos. A maior concentração de pontos de avulsões ocorre na porção da baixa Bacia Bananal (região da Ilha Bananal), com 81% ou 56 12 pontos de avulsões. Avulsão foi o principal mecanismo nesse tempo, gerando um padrão anabranching de canais ativos, paleocanais e rios subadaptados (underfit rivers). Nas áreas mais baixas da Planície Bananal, como na Ilha do Bananal, onde a superfície plana é pobremente drenada e encharcada por um longo período (dezembro a maio) favorece o desenvolvimento de vegetação mais tolerante à inundação, como os tipos herbáceos do bioma Cerrado (Campo Limpo e Campo Cerrado). Consequentemente, esse ambiente encharcado inibe o crescimento dos tipos fisionômicos mais densos (Cerrado s.s. e Cerradão). Desta forma, a distribuição espacial das fitofisionomias do bioma Cerrado na Ilha do Bananal é controlada, principalmente, por inundações prolongadas, variações das formas geomorfológicas e secundariamente por avulsões dos cinturões fluviais (eventos neotectônicos). Finamente, os registros obtidos na Planície Bananal lançam novas luzes para o entendimento das condições paleohidrológicas do Brasil Central e fornecem importantes informações para a área de transição entre os biomas Cerrado e Amazônico. 13 REFERÊNCIAS BIZZI, L. A.; SCHOBBENHAUS, C.; VIDOTTI, R. M.; GONÇALVES, J. H. 2003. Geologia, tectônica e recursos minerais do Brasil. Serviço Geológico do Brasil, Brasília, 673p. LATRUBESSE, E. M. 2003. The Late Quaternary Paleohydrology of Large South- American Fluvial Systems. In: 3rd Latinoamerican Congress of Sedimentology, 193-212. LATRUBESSE, E. M., STEVAUX, J. C. 2002. Geomorphology and environmental aspects of the Araguaia fluvial basin, Brazil. Zeitschrift fur Geomorphologie, 129:109-127. MITTERMEIER, R. A.; MYERS, N.; THOMSEN, J. B.; FONSECA, G. A. B. OLIVIERI, S. 1998. Biodiversity Hotspots and Major Tropical Wilderness Areas: Approaches to Setting Conservation Priorities. Conservation Biology, 12(3):516- 520. MYERS, N; MITTERMEIER, R.A.; MITTERMEIER, C.G; FONSECA, G.A.B; KENT, J. 2000. Biodiversity hotspots for conservation priorities. Nature, 403:853- 858. 14 PAPER I Geology and regional geomorphology of the Araguaia River Basin, Central Brazil: Part 1 – Geology* *To be submitted to the Journal of South American Earth Sciences 15 Geology and regional geomorphology of the Araguaia River Basin, Central Brazil: Part 1 - Geology C. R. Valente1; E. M. Latrubesse2 1Federal University of Goiás-UFG, Physical Geography and Geology Lab Campus Samambaia – 74.001-970 Goiânia, GO, Brazil E-mail: cidvalente@go.cprm.gov.br 2Universidad Nacional de La Plata, FCNyM, Instituto de Geomorfologia y Suelos-IGS Calle 3 N 584, (1900), La Plata, Argentina E-mail: latrubesse@igs.edu.ar Abstract A general review of existing data with some updates and modifications on geotectonics and geology of the Araguaia River Basin in Central Brazil region is presented. In this region, the geology consists of rocks with ages, evolution and distinctive structural patterns, which were generated in varied paleoenvironments (marine, fluvial, lacustrine, desertic, and volcanogenic). The oldest rocks consist of Archean to Paleoproterozoic ensialic basement (Goiás Massif, Rio Maria, Iriri-Xingu, and Porto Nacional-Nova Crixás). The Neoproterozoic supracrust rocks comprise the magmatic island arcs (Goiás Magmatic Arc) that limit these old nuclei and metasedimentary folded belts (Araguaia and Paraguay belts). These mobile belts were amalgamated during the Brasiliano Cycle (630-899 Ma) through the continental collision between the Amazon and the São Francisco cratons. Fault systems control the gold, copper-gold, and emerald deposits associated to the greenstone belts and metavolcano-sedimentary sequences. The geological development of the intracratonic sedimentary basins of Paraná and Parnaíba provinces evolved during the Paleozoic and Mesozoic with a deposition that was influenced by the geodynamics of the Gondwana. Fluvial sediments of the Bananal Basin characterize the Quaternary in the region. The Precambrian regional structure is made up of several continental blocks limited by major crustal sutures that are associated with strike-slip faults and thrust fault systems. Evidences of neotectonic events are related to a shear zone reactivated in Paleozoic and Cenozoic, whose movements persist up to the present day through the Goiás- 16 Tocantins Seismogenic Zone (GTSZ). Digital data from Landsat ETM, SRTM, and aerogeophysical images were processed, interpreted and compared with field data and integrated in GIS environment for the geological and tectonic mapping. This study has as its main objective the use of interpretation techniques of remote sensing products in the definition and characterization of the geological and deformational properties of the Araguaia River Basin region. Keywords: Geology; Geotectonics; Araguaia River Basin 1. INTROCUCTION Significant advancements were obtained on the geology of Brazil during the last decades. From the cartographic viewpoint the information was united in the recent work of the Geological Survey of Brazil, published in 2003 through the Geology, Tectonics and Mineral Resources of Brazil, with maps at 1:2.500.000 and 1:1.000.000 scales, in GIS environment. It synthesizes the geological information amassed over 30 years by this company, universities, and mining companies. Despite these significant advancements, the geology of Brazil’s central region generally possesses fragmented and punctual information and in many areas the scientific knowledge is quite scarce. In particular, the geological environments of economic interest have received greater attention due to high mining potential, for example, the Greenstone Belt areas (Crixás, Goiás Velho, Guarinos) and the Mafic- Ultramafic Complexes of Goiás (Barro Alto, Niquelândia, and Canabrava). On the other hand, the Araguaia River is the biggest fluvial system that drains the Cerrado biome. One must be reminded that 75% of the Cerrado savanna has suffered deforestation that has been accelerated due to the expansion of the agricultural frontier since the 1970s. Moreover, inside the Araguaia fluvial basin can be found the intracratonic basin constituted by Quaternary sediments, called Bananal Basin, with approximately 106,000km² that extends along 800km of length. In the north portion of this fluvial basin stands the Bananal Island plain with 20,000km². Bananal Island is an area of environmental conservation that contains Araguaia’s National Park and some 17 aboriginal reserves, where valuable information on the paleoenvironment of the Quaternary and of the present can be found; therefore, it represents the last still preserved regions of the Cerrado biome. A good part of the existing information on the geology of the Araguaia Basin and of the Center-West, in general, is not available in the international literature. Generally, they are internal reports or published in regional symposia or national congresses by government agencies, mining companies and universities, including academic theses. The geographic clipping in the Araguaia fluvial basin is justified from the geological viewpoint because it allows for the understanding of the geological reorganization of the landscape of the Late Cenozoic until acquiring the present physiognomy, which caused the formation of the biggest Brazilian intracratonic sedimentary basin in recent times, the Bananal Basin. Apart from that, the geographic clipping is also justified because, in Brazil, hydrographical basins represent a basic element in the management of natural resources and the territorial order where the geological study is a fundamental part. The presentation of a review of the existing data of the entire geological column and their geotectonic characteristics is fully justified in order to supply the international scientific community with an integrated vision of this enormous and important region in a succinct form and a set of bibliographical references of Brazil to be divulged. In this form, this study has as general objective a review of the preexisting works of geology with some data updates. The specific objectives were to characterize the main evidences of the different tectonic movements and to define the tectono- geological evolution. 2. STUDY AREA This study was developed in the Araguaia River Basin, in Brazil’s central region. With an area of approximately 384,600 km² (Fig. 1), it is located between meridians 18 47º47`34`` and 55º24`08`` of west longitude and parallels 5º22`15`` and 18º17`12`` of south latitude. Fig. 1 - Location of the study area in Central Brazil. In the study region there is vegetation of the Cerrado and Amazon biomes. The tropical rainforest of the Amazon biome is dominant in the southeast of Pará state. The Cerrado is more expressive and consists of Cerrado woodland, wooded Cerrado, shrub Cerrado and Cerrado grassland physiognomies, as well as gallery forest along the floodplain belts. This region underwent an intense occupation process during the 70s and 80s, with deforestation of the Cerrado and Amazon biomes for the implantation of agriculture and cattle breeding. The climate corresponds to the Aw in Koppen´s Climatic Classification. It is characterized by two well-defined seasons: six months of wet condition, from November to March, and six months of dry condition, from April to September. The annual mean rainfall of the region varies from 1,400 to 2,200 mm/year. The annual 19 mean temperature increases northward, varying between 22ºC and 26ºC, with the maximum (38º) occurring in August and September and the minimum (22ºC) in June. The Araguaia River is usually divided into three main parts, according to the hydrologic conditions and river regimes: Upper, Middle, and Lower Araguaia. Phanerozoic sedimentary rocks of the Paraná Province characterize the geology in Upper Araguaia Basin. The Middle Araguaia is constituted predominantly by Quaternary Bananal Basin sediments and subordinately by Precambrian basements of the Goiás Massif, Goiás Magmatic Arc, Porto Nacional-Nova Crixás, and Araguaia and Paraguay Belts. The Low Araguaia is represented by Araguaia Belt and Paleozoic/Mesozoic covers of the Parnaíba Province, as well as Precambrian basements of the Amazon Craton (Rio Maria and Iriri-Xingu Domains). 3. MATERIALS AND METHODS The cartographic representation of the structural provinces was obtained mainly from GIS Project of Brazil (Bizzi et al., 2003), at 1:1.000.000 scale, with some adaptations and data updates. For the vertical or chronologic sequence of geological units in a region, we used the geological column from International Commission on Stratigraphic (ICS) and published in 2006. For the elaboration of the geotectonic and structural maps, we used visual interpretation techniques of the image spatial attributes of Landsat ETM+ (Enhanced Thematic Mapper Plus) and interferometric data from SRTM (Shuttle Radar Topography Mission), as well as aerogeophysical data (magnetometry, gamma-ray spectrometry, and gravimetry). This interpretation was complemented with activities of digital processing of images (ENVI) and integration with a Geographic Information System (ArcMAP). Through the StereoNet for Windows Version 3.03 was constructed rose diagrams of the structural lineaments extracted from remote sensing products and field data. Fieldwork was developed during 35 days in the dry season, in order to know and describe characteristics of the morphological features, types of rocks and fracture data, excavation of trenches, drill holes and profiles in Araguaia River with the support of a 20 boat. This fieldwork was carried out in two periods, the first from August to September 2005 and the second in August 2006. 4. STRUCTURAL PROVINCES Almeida et al. (1977, 1981) introduced the concept of Structural Province and identified ten provinces in the Brazilian territory. Six structural provinces cover the study area and are discussed herein, namely Tocantins, Carajás, Central Amazônia, Paraná, Parecis, and Parnaíba (Fig. 2). These provinces were individualized according to geochronological and geophysical-structural models. Their distributions are in agreement with the geochronological provinces established in previous works (Cordani et al., 1979; Almeida et al., 1977, 1981; Pimentel et al., 1991; Pimentel and Fuck, 1992; Tassinari et al., 1997; Cordani and Sato, 1999; Lacerda Filho et al., 1999; Pimentel et al., 2000, 2003; Santos, 2000, 2003; Bizzi et al., 2003). 4.1. Tocantins Province The Tocantins Province is the most extensive geotectonic unit ca. 63% of the study area, situated in the eastern part of the area (Fig. 2). The Province corresponds to a large Neoproterozoic orogenic zone related to the Brasiliano-Pan African orogenesis. This orogeny was formed between 1.0 Ga and 0.6 Ga and is represented by the Brasília, Araguaia, and Paraguay belts and by large juvenile magmatic arcs with ca. 0.9-0.64 Ga, like Mara Rosa and Arenópolis arcs (Pimentel et al., 2000; Dardenne, 2000). The main characteristics of the structural and geological provinces are summarized in Table 1 and discussed below. The basement of the study area is made up of Archean granite-greenstone (Goiás Massif) and Paleoproterozoic terrains (Porto Nacional-Nova Crixás and Rio dos Mangues Complex). These cratonic fragments took part in the collision between the large continental masses of the Amazonian and São Francisco cratons (Cordani and Sato, 1999; Pimentel et al. 2003). Several works consider the subdivision of the Tocantins Province (Almeida et al., 1977; Fuck et al., 1993; Fuck, 1994; Pimentel et 21 al., 2000). However, in this paper we used the division of the Geological Survey of Brazil (Bizzi et al., 2003) with adaptations and some alterations. Fig. 2 - Tectonic and geological domains in the Araguaia River Basin. 22 Table 1 - The main characteristics of the structural provinces of the study area. 4.1.1. Goiás Massif Goiás Massif constitutes the oldest tectonic unit in the study area. This Meso to Neoarchean basement covers an area of ca. 21.300km² or 5,5% of the Tocantins Province. Goiás Massif is constituted by several greenstone belts (Crixás, Pilar de STRUCTURAL GEOLOGICAL GEOLOGICAL PERIOD/EPOCH/ AREA PROVINCES PROVINCES UNITS AGE (Km²) (%) Bananal Basin Araguaia Formation Quaternary 105.965 27,46 Água Branca Basin Agua Bonita Formation Silurian/Devonian 608 0,16 Couto Magalhães, Morro do Neoproterozoic Araguaia Belt Carom, and Xambioá formations (Tonian) 55.865 14,75 Foreland Basin Diamantino Formation Neoproterozoic 11.475 2,73 Cuiabá and Nova Xavantina Neoproterozoic Paraguay Belt groups (Cryogenian) 11.285 2,92 Orthogneissis of the West of Goiás and Metavolcanosedimentary Sequences (Bom Jardim, Iporá-Amorinópolis, Arenópolis- 21.342 5,53 Piranhas, Jaupaci, Anicuns- Itaberaí, Mara Rosa) and Syn- Goiás magmatic Arc Late orogenetic granites Neoproterozoic 630-899 Ma U-Pb (SHRIMP)¹,² Rift Basin Serra da Mesa Group Paleoproterozoic 481 0,12 Porto Nacional- Paleoproterozoic Nova Crixás Domain Campo Maior and Rio dos Mangues complexes 2.12-2.0 Ma (Pb- Pb) 14.237 3,69 TOCANTINS Goiás Massif Greenstone belts and TTG terrains: Granitic-Gneiss Complexes (Uvá, Caiçara, Anta, Caimar, Hidrolina, Muquém) and greenstone belts (Crixás, Goiás, Pilar de Goiás, and Guarinos groups). Meso to Neoarchean 2.85- 2.70 Ga U-Pb (SHRIMP)¹,² 3.0 ± 0.14 Ga (Sm-Nd)³ 21.352 5,52 Bauru Basin Bauru Formation Cretaceous 9.824 2,54 Botucatu and Serra Geral Serra Geral Basin formations Jurassic-Cretaceous 7.548 1,95 Aquidauana, Corumbataí, Furnas, Paraná Basin Ponta Grossa, and Vila Maria PARANÁ formations Silurian-Triassic 64.045 16,59 Grajaú Basin Itapecuru and Codó formations Cretaceous 1.790 0,46 Pastos Bons and Corda formations Alpercatas Basin (Mearim Group) and Mosquito Jurassic 1.395 0,36 Formation Pimenteiras, Cabeças, Longá, and Poti formations (Canindé Group). Piauí, Pedra-de-Fogo, Motuca, and Sambaíba formations PARNAÍBA Parnaíba Basin (Balsas Group) Devonian- Carboniferous 18.724 4,85 Salto das Nuvens and Ronuro PARECIS Parecis Basin formations Cretaceous- Neogene 1.728 0,45 Paleoproterozoic Iriri-Xingu Domain 1.8-1.7 Ga U-Pb CENTRAL AMAZONIA Iriri Group, Xingu Complex, and Tarumã Granite (SHRIMP)4 4.960 1,28 TTG intrusons, Quixadá, and Mesoarchean CARAJÁS Rio Maria Domain Tocandera formations and 3.0-2.8 Ga U-Pb Sapucaia Group (SHRIMP)4,5 33.752 8,74 References by ages: ¹Pimentel et al. (2000); ²Pimentel and Fuck (1994); ³Fortes et al. (2002); 4Santos et al. (2000); 5Santos (2003) 23 Goiás, Guarinos, and Goiás Velho groups). This geotectonic unit presents the following units from base to top: (a) komatiitic and tholeiitic ultramafic metavolcanic rocks; (b) tholeiitic metabasaltic rocks; (c) detrital and chemical metamorphic sedimentary rocks, sometimes associated with pyroclastic rocks (Kuyumijian and Dardenne, 1982; Danni and Jost, 1986; Fortes and Nilson, 1991; Magalhães and Nilson, 1993; Jost et al. 1995). The komatiitic rocks of these greenstone belts were dated and produced Sm-Nd isochronic ages of 2.82 ± 0,098 Ga (Arndt et al., 1989) and 3.00 ± 0,09 Ga (Fortes et al., 2002) . The Crixás greenstone belt is the most preserved, revealing pillow lava structures and spinifex textures. The main deposits of Au occur in association with Crixás greenstone belt, called Mine III/New Mine with 65t Au and exploited since 1990 with an annual output of 4,5t Au (Yamaoka and Araújo, 1988). The greenstone belts are limited by TTG (tonalite, trondhjemite, and granite) allochthonous blocks through shear zones or thrust faults of mainly NW-SE trend, named Uvá, Caiçara, Anta, Caimar, Muquém, and Hidrolina. These granite-gneissic complexes presented U-Pb ages varying between 2.84-2.70 Ga (Queiroz et al., 1999; Pimentel et al., 2000) and were affected by three tectono-metamorphic events with U- Pb ages at 2.7 Ga and 2.01 Ga (Pimentel et al., 2000) and 590 Ma (Queiroz et al., 1999) which correspond, respectively, to Jequié, Transamazonian, and Brasiliano orogenic cycles. 4.1.2. Porto Nacional-Nova Crixás Domain The interest area of this study occupies part of the Porto Nacional-Nova Crixás Domain, situated in the eastern portion of the researched area. This domain covers a middle and high-grade gneiss belt of NE-SW trend, which is mostly unknown in the south segment. Porto Nacional-Nova Crixás Domain is represented by the following units: (1) gneiss and granulite rocks of the Porangatu Complex; (2) orthogneiss and calci-sillicate rocks of the Rio dos Mangues Complex with a U-Pb SHRIMP age of 2.2 Ga (Fuck et al. 2001) and Pontal Orthogneiss with a U-Pb age at 2.15 Ga, dated by Gorayeb et al. (2000); (3) the volcano-sedimentary sequence of the Rio do Coco 24 Group and granitoids of the Serrote Suite of extensional environment with an age of 1.85 Ga (Souza and Moura, 1996). In the Gurupi region, the Rio dos Mangues Complex is constituted by granodiorite and tonalite rocks that are generally mylonitized and deformed by ductile shear zone of N20º-40ºE direction, related to dextral strike-slip fault from Transbrasiliano Lineaments (Frasca et al., 2005). These rocks reveal calci-alkaline affinity, interpreted as accretionary magmatic arc to the Sanfranciscana microplate, with important mineralizations of tourmaline, garnet, and cyanite generated during the Brasiliano Cycle at 551±4 Ma in garnet (Frasca et al., 2005). 4.1.3. Rift Basin The Rift Basin related to Statherian taphrogenesis evolved towards an intracratonic basin in Paleo to Mesoproterozoic, during which it was filled by sediments and continental bimodal volcanism with intrusions of anorogenic granites (Pimentel et al., 1991). This basin is characterized by important post-rift marine transgressions, constituted by beds of quartzite and metapelites deposited in shallow platform, related to Serra da Mesa and Serra Dourada groups that constitute the metamorphic equivalent of the marine sediments of the Araí Group (Braun and Baptista, 1978; Marini et al., 1984; Dardenne, 2000) and of the Natividade Group (Gorayeb et al., 1988). The more expressive outcrops occur in Serra Dourada, located in the southern to southwestern regions of Goiás city, where metasediments constitute mountains in NE- SE to E-W trend limited by thrust faults. In this region can be found the basal unit of the Serra Dourada Group that consists of quartzite, arkose-quartzite and levels of intraformational metaconglomerate. 4.1.4. Goiás Magmatic Arc The Neoproterozoic Goiás Magmatic Arc comprises a series of juvenile magmatic arcs defined mainly by frontal trusting and lateral ramp systems of more than one episode of deformation during the Brasiliano Orogenic Cycle, between 900 25 and 630 Ma (Pimentel and Fuck, 1992, Pimentel et al., 1991, Pimentel et al., 1997; Junges et al., 2002). These arcs are mostly formed by Neoproterozoic island-arc terrains consisting of tonalitic to granodioritic orthogneisses, volcano-sedimentary associations and late- to post-orogenic intrusions of granites and gabbros (Pimentel et al., 1999). According to Delgado et al. (2003) there are three large-scale tectonic episodes in the Brasiliano Cycle: (i) The Brasiliano Orogenic System I (900-700 Ma), with a collisional peak at 790 Ma, encompasses the first subduction-related plutono-volcanic intra-oceanic accretionary arcs; (ii) The Brasiliano Orogenic System II (640-610 Ma) is characterized by collision-related orogens with a metamorphic peak at 632 Ma with recycling of crustal material and limited juvenile accretion; (iii) The Brasiliano Orogenic System III (600-520 Ma) comprises the most recent system of orogens. This system marks the transition to a stable environment in the South American Platform. The Goiás Magmatic Arc has been identified in two localities, separated by Neoarchean granite-greenstone terrains (Fig. 2), called Mara Rosa Arc in the northern segment and Arenópolis Arc in the southern segment (Pimentel et al., 2000; 2003). The Goiás Magmatic Arc contains several deposits of Au and Au-Cu originated in the diverse periods of evolution. Oliveira et al. (2000) included these mineralizations in the Arenópolis-Mara Rosa Gold-Copper Belt, where occur the deposits of Au (Posse and Fazenda Nova), Cu-Au (Chapada and Bom Jardim), Au-Bi (Mundinho), and Au- Ag-Ba (Zacarias). In addition, in the Mara Rosa Magmatic Arc contains important emerald “garimpos” (Santa Terezinha de Goiás) that have been exploited since 1981 with an output estimated at 150 to 200t of emeralds and green beryls (Biondi, 1990). In this context, the Mara Rosa Magmatic Arc is formed by metatonalite and metadiorite affinity rocks associated with narrow NW-SE belts of volcano- sedimentary sequences; these are constituted of basic to felsic metavolcanic rocks and detrital to chemical metasedimentary rocks metamorphosed in greenschist to amphibolite facies conditions (Arantes et al. 1991). Pimentel et al. (1997), by means of the U-Pb SHRIMP method, dated the Posse Gold Mine with values of 862 ± 8 Ma (crystallization age for the felsic rock) and 632 ± 4 Ma in titanite (metamorphic age of the Brasiliano II). The dominant structural pattern of the Mara Rosa Arc is oriented in 26 the N20-30E trend, where the rocks are folded and deformed by thrust fault and strike- slip-faulting of the Transbrasiliano Lineaments. The Arenópolis magmatic arc is known in southwestern and southern regions of Goiás city and contains a series of coalescent arcs and volcano-sedimentary sequences. These sequences occur as narrow bodies that are elongated parallel to the NNW and NNE strike-slip faults between Bom Jardim de Goiás and Firminópolis (Pimentel et al., 2000). These belts are separated by orthogneiss terrains (granite, tonalite and granodiorite) generally with mylonitic structure. In this region are represented from west to east by the following sequences: Bom Jardim de Goiás and Arenópolis- Piranhas with U-Pb age of 928±8 Ma (Pimentel et al., 1991) and metamorphic age of 594 Ma; Iporá-Amorinópolis encompasses the zircon U-Pb age of 636 ± 6 and 597 ± 5 Ma (Rodrigues, 1996) which represents the end of the Brasiliano II; Jaupaci Sequence reveals a zircon U-Pb age dated by Pimentel and Fuck (1994) at 764±14 Ma; it represents a formation age and 600 Ma metamorphism age of the Brasiliano II and Anicuns-Itaberaí with an age of 860 Ma. 4.1.5. Araguaia Belt The Araguaia Belt in the context of the Tocantins Province is located in its northern portion and reveals a general N-S direction, with a dimension around 1,000 km of length and 150 km of average width. It constitutes the north extension of the Paraguay-Araguaia Belt bordering the eastern part of the Amazon Craton (Central Amazon and Carajás provinces). In the area of study, the Araguaia Belt is represented by its southern segment, where it is constituted mainly by pelite-psammite metasedimentary rocks, locally with carbonate facies, attributed to the Baixo Araguaia Group (Couto Magalhães, Xambioá, Pequizeiro, and Campo Maior formations). The metamorphic grade varies from low greenschist to amphibolite facies conditions (Souza and Moreton, 1995; Frasca and Araújo, 2001; Alvarenga et al., 2000). Remnants of Proterozoic oceanic crust occur in restricted areas that are constituted by mafic-ultramafic rocks of the Serra do Tapa and Quatipuru (Souza e 27 Moreton, 1995), as well as diverse granitic intrusions. Colméia, Lontra, and Xambioá complexes represent dome structures of gneissic basement. The Xambioá Complex presents a Pb-Pb age of 2,85 Ga (Moura e Souza, 1996; Moura e Gaudette, 1999). This orogenic belt possesses a prominent planar foliation, generated by progressive tangential efforts, directed westwards against the Amazon Craton. This tectonic movement provided the development of the ductile shear zone with a displacement of surfaces and shear structure of low angle (frontal ramps of N-S direction) developed during the Brasiliano Orogenic System II (650-600 Ma). Structural analyses suggest a westward crustal shortening and tectonic transport towards NW, indicating an oblique collision (Brito Neves et al., 1999). 4.1.6. Paraguay Belt It constitutes a mobile belt situated in the occidental portion of the Tocantins Province (Almeida et al. 1977), deposited in the border to the south of the Amazon Craton and to the east of the Apa River Block, in Mato Grosso do Sul. This geological province is characterized by a sequence of metasedimentary rocks that are folded and deformed by high angle reverse faults during the Brasiliano Orogenic System III, between 590-500 Ma, with post-orogenic granitic magmatism represented by granites of the São Vicente Suite (550-500 Ma). Alvarenga and Trompette (1993) separate these metasediments of low-grade metamorphism (Cuiabá Group) into two structural zones: lower detrital unit and claciomarine/turbiditic unit. The lower unit is composed of graphitoid phyllite, phyllite, quartzite, and dolomite; and the upper unit represented by a stratigraphic sequence deposited during the glaciation of the end of the Upper Proterozoic, formed for dyamictite and turbidite. In the area under study, metasedimentary rocks of this geological province occur in a narrow belt between the sediments of the Paraná and Bananal basins, located in the south portion of the study area. In the New Xavantina region occurs a sequence of metavolcano-sedimentary rocks correlated to the basal portion of the Cuiabá Group. This sequence consists of metavolcanic rocks of mafic to intermediate compositions, 28 intercalated with cherts and BIFs in the base, while the upper portion is dominated by pelitic-psammitic metasediments. According to Martinelli (1998), important auriferous mineralizations in the “Garimpo” Araés (Nova Xavantina) can be found in quartz veins associated to the dextral transcurrent fault, with an ENE-WSW trend. However, the gold quartz veins in the “Baixada Cuiabana” (Jardim Itália, Casa de Pedra and “Garimpos” of CPA, Mineiro, and Abdala, among others) occur filling fractures along the NW-SE direction in phyllite, siltstone, and quartzite attributed to the Cuiabá Group. 4.1.7. Foreland Basin In the Cuiabá-Província Serrana region, the foreland basin is oriented around N60-70E in its northern portion and passes gradually to N25E in the southern portion. It consists of a carbonate sequence (Araras and Guia formations) that is under the upper detrital sequences (Raizama and Diamantino formations). The rocks of this domain were affected by a low-grade metamorphism (Alvarenga 1990) characterized by ruptile tectonics that is itself manifested by normal faults and by open folds, with subvertical axial plans, that moves towards the Paraguay Belt through inverse folds to isoclines. The axial plans exhibit low-dips for southeast with a northward vergence, in the direction of the Amazon Craton (Almeida, 1984; Luz et al., 1980; Alvarenga, 1990; Alvarenga et al. 2000). The representative unit is the Diamantino Formation constituted by shales, argillites, siltstones, and arkoses. 4.1.8. Água Bonita Basin The sediments of this basin are confined inside the lineament system of the NE- SW trend, located between the Porto Nacional-Nova Crixás Domain and the Araguaia Belt. These sediments occur in a narrow area around 7km of width and 83km long parallel to these lineaments, called Transbrasiliano Lineaments. The reactivation of these structures in the graben system allowed the preservation of sedimentary units, mainly molassic. The Água Bonita Formation of the Silurian-Devonian period 29 (Schobbenhaus et al., 1975) is constituted by medium to coarse sandstone, with intercalations of siltstone and locally with conglomeratic facies. 4.1.9. Bananal Basin The Bananal Basin, represented by Pleistocene alluvial sediments of the Araguaia Formation, is a flat surface of low slope with an area close to 106,000km² and corresponds to 27% of the surface of the study area. The pioneering work of Barbosa et al. (1966) defined the Araguaia Formation as being formed by a succession of continental sediments that are initiated by a basal conglomerate (with thickness of up to 3m) covered by yellowish sands or brownish, silty, ferruginous, consolidated to unconsolidated ones, with varied colors and textures Pena et al. (1975) executed a drill hole 47,90m of deep in the Bananal Basin (in Canada farm). In this locality the Araguaia Formation is 45,50m thick with metrical to decimetrical intercalations of sands, silts, and clays. The sandy sediments are predominant among the coarse textures. These sediments present a generally yellowish to reddish coloration with a variation of white and gray. In the interval of the profile between 25,00 to 29,00m of depth, there is a level of fine to medium sand with intercalations of clay and of indurated sandy sediment enriched in iron oxide. Fieldwork executed by Valente and Latrubesse (2007) in the Bananal Island plain and in the Araguaia River bank showed that the Araguaia Formation is constituted by an upper stratum of indurated gray-clear clay up to 3,00 m which overlaps sandy sediment strata of fine to medium textures with clay intercalations. The occurrence of indurated sand layers enriched in iron oxide of reddish colouring is common. Tertiary to Quaternary lateritic crusts occur in several localities, for example, in the Bananal Island and in the western region of the Cocalinho and Aruanã, as product of intense weathering made up of mineral assemblages with rich concretions in Fe-Al oxides. These laterites developed in a drier climatic environment than the present one. 30 4.2. Paraná Province The Paraná Province is located in southern Brazil, with an area of about 1,050,000km² and a NNE-SSW-trending elliptical shape that evolved during the Paleozoic and the Mesozoic. In the study area, the Paraná Province occurs in the southern part with an area of 81,417km² or 21,08%. It is a flexural intracratonic basin of polycyclic evolution. The deposition began in the Ordovician within an intracratonic rift of the basement as an Interior Fracture (IF) type basin. The known tectono-stratigraphic record suggests that the orogenic activity in the boundaries of the South American Plate had influenced the intraplate regime regarding to the events of subsidence, uplift and magmatism. Zalán et al. (1990) suggest that the Paraná River Basin corresponds to the overlapping of some basins on the same plate. According to Milani and Thomaz Filho (2000), this province includes three areas of independent sedimentation, separated by deep discordances: The Paraná, Serra Geral and Bauru basins (Fig. 3). Fig. 3. Tectonic evolution of the Paraná Province (modified from Pedreira et al., 2003). IF-Interior Fracture, IS-Interior Sag, MS-Marginal Sag, MSIS-Marginal Sag/Interior Sag. 31 In Paraná Province there are kimberlitic provinces of the Upper Cretaceous which are related to Lineaments AZ-125º (Gonzaga and Tompkins, 1991). In the Diorama region there is several diamond “garimpos” in alluvial deposits along the Caiapó and Pilões rivers that are oriented in Lineaments AZ-125º. In Arenópolis/Nortelândia the diamond deposits with 400,000 carats and content of 2 to 4 points/m³ are resultant from the erosion and concentration of diamonds in placer type deposits during the Tertiary-Quaternary (Fleischer, 1998). 4.2.1. Paraná Basin Paraná Basin consists of four cycles of subsidence that correspond to the second- order allostratigraphic units or supersequences: the rift phase represents the Rio Ivaí Supersequence and the syneclise phase corresponds to Paraná, Gondwana I, and Gondwana II supersequences (Milani, 1997). This last basin occurs outside of the study area. The top of this Supersequence is defined by a discordance surface that deeply eroded the package and established a wide and regular peneplain (Milani and Ramos, 1998). The Rio Ivaí Supersequence constitutes a transgressive cycle that in the study area is represented by the Vila Maria Formation (Rio Ivaí Group), which is made up of dimictites, shales, fossiliferous siltstones, and sandstones. The rocks of this formation are distributed along a narrow belt between the Neoproterozoic basement (Goiás Magmatic Arc and Paraguay Belt) and the Paraná Basin (Furnas Formation). The Paraná Group is constituted, in its northern portion, by the Furnas (base) and Ponta Grossa (top) formations. The basal contact with the Rio Ivaí Group and the upper one with the Aquidauana Formation are erosive discordances. The Devonian record in the Paraná Basin begins with the Furnas Formation, a sandy package of accumulated tabular geometry on a wide and stable peneplain post- ocloyic orogeny (Milani and Ramos, 1998). It represents a transgressive-regressive cycle and is made up of a predominance of rocks deposited in fluvial and transitional environments that encompass sandstones and conglomerates, with abundant icnofossils. The Ponta Grossa Formation is mainly constituted by shales and divided 32 into three members, of which the lowest one, marine, corresponds to the surface of maximum flooding of the Devonian. The Aquidauana Formation that occurs in the study area is an integrant part of the Gondwana I Supersequence and represents the widest sedimentary area of the Paraná Basin. This formation, attributed to Late Carboniferous-Early Permian glaciation of Gondwana, has been divided into three stratigraphic units (Schneider et al., 1974): (a) Lower unit formed by red to whitish sandstones, diamictites and conglomerates; (b) Middle unit is constituted by siltstones, shales, sandstones, and diamictites; (c) Upper unit consisting of red sandstones with cross stratification. The depositional environment interpreted by Schneider et al. (1974) is continental, with fluvial and lacustrine deposits and glacial influence. 4.2.2. Serra Geral Basin The Serra Geral Basin is constituted by Botucatu and Serra Geral formations (São Bento Group). According to Scherer (2002), this basin can be divided into two genetic units: a lower unit, with maximum thickness of 100 m, corresponding to the Botucatu Formation. The Botucatu desert is constituted by aeolian sand deposits forming sets and cosets of cross-bedded strata and deposits of conglomerates and conglomeratic sandstones related the local occurrence of ephemeral rivers. The upper unit consists of volcanic rocks of the Serra Geral Formation. It encompasses a succession of flows around 1.500m thick constituted by a bimodal tholeiitic sequence where basalt to andesitic basalt rocks (> 90% in volume) are predominant, overlapped by rhyolite and rhyodacite rocks. The Serra Geral Formation marks the end of the Eocretaceous magmatic episode of infillings this geological province which corresponds to one of the biggest volcanic events in the world (Saunders et al., 1992). It is related to the fragmentation of west Gondwana through the generation and extraction of magma that is linked to mantle dynamics of the Tristão da Cunha plume. Ar-Ar radiometric dating sets its beginning at 137,4 Ma and the end at around 128,7 Ma (Turner et al., 1994). 33 4.2.3. Bauru Basin The sedimentary Bauru Basin is essentially constituted by sandy continental deposits, with subordinate volcanic rocks, installed on the area of occurrence of basaltic lavas of the Serra Geral Formation during the Neocretaceous (Fúlfaro et al., 1982; Fernandes, 1992; Coimbra and Fernandes, 1994). This basin consists of two chronocorrelate units (Fernandes and Coimbra, 2000). The Bauru and Caiuá groups are representative of the same environment, under a hot climate that is semi-arid in the borders, and desertic in the interior of the basin. The Upper Cretaceous Bauru Group is a package of alluvial, fluvial, and eolian sedimentary rocks that closed the depositional history of the Paraná Basin (Milani and Zalán, 1999). 4.3. Parnaíba Province Góes and Feijó (1994) divide the Parnaíba Structural Province into four basins separated by unconformities: Parnaíba, Alpercatas, Grajaú, and Espigão-Mestre basins. According to the global classification of basins of Kingston et al. (1983), these sedimentary basins were classified by Pedreira et al. (2003) in: the first of the IF/IS- type (Interior Fracture/Interior Sag), the second of the IF-type (Interior Fracture), the third of the MS-type (Marginal Sag) and the fourth of the IS-type (Interior Sag). This last basin does not occur in the study area. 4.3.1. Parnaíba Basin The Paleozoic/Mesozoic Parnaíba Basin, in the area under study, is oriented as a SW-NE belt. This basin was implanted on the Cambrian-Ordovician rifts of Jaibaras, Jaguarapi and others (Brito Neves, 1998), therefore being a basin of the IF/IS type (Pedreira et al., 2003) represented in the study area by Canindé, Balsas, and Mearim groups, as well as by Mosquito, Codó, and Itapecuru formations. The Canindé Group is formed from base to top by Pimenteiras, Cabeças, Longá, and Poti formations. The Pimenteiras Formation consists of sandstone with levels of 34 shales, deposited in an environment which is dominated by tides and storms. The Cabeças Formations consists of sandstones with diamictite intercalations that are interpreted by Góes and Feijó (1994) as neritic platformal environment deposits, with a periglacial influence. The Longá Formation consists of fine sandstones and siltstones. The Poti Formation is represented by sandstones, shales, siltstones, argillites, and conglomerates. Góes et al. (1997) interpreted this formation as deposited in environments of upper and lower sub-tide, fluvio-estuarine channel and tidal plain, under climatic conditions of dryness. The Balsas Group is formed by Piauí, Pedra-de-Fogo, Motuca and Sambaíba formations that are attributed to the Carboniferous-Triassic. The Piauí Formation consists of aeolian dune deposits; inter dunes and deflation plains, containing sandstone, argillite, shales, siltstones, and limestones. The Pedra-de-Fogo Formation is constituted by sandstones, shales, siltstones, limestone, evaporate, and silexite deposited in tide plains. The Motuca Formation consists of red shales with levels of siltstones, locally with dome stromatolite representing lacustrine environment. Finally, the Sambaíba Formation is formed by aeolian fine sandstone. 4.3.2. Alpercartas Basin This unit represents an intracratonic basin with sedimentary rocks and volcanic masses of flows, tuffs and other materials, brought to the surface through faults and forming piles. The Alpercatas Basin is located between the Parnaíba and Grajaú Basin. It is formed by a system of rifts which are filled by the Jurassic supersequences, formed by the Pastos Bons and Corda formations (Mearim Group) limited by the Mosquito Formation. The Pastos Bons Formation is a sequence of shales and sandstones that is interpreted as fluvial and aeolian environment deposits. The Corda Formation consists of reddish sandstones with bimodal granulometry in sequences separated by surfaces where clay deposition occurs. The environment of sedimentation is interpreted as desertic. The Mosquito Formation is formed by black tholeiitic basalt that occasionally 35 possesses intercalations of sandstones. The associated dikes were dated by Ar-Ar at 198 Ma (Marzolli et al. 1999). 4.3.3. Grajaú Basin This basin is located to the north of the Alpercatas Basin. It is attributed to the Cretaceous and includes, in the study area, the Codó and Itapecuru formations. The Codó Formation is composed of shales, limestones, and evaporites (Paz and Rossetti, 2001). In the Itapecuru Formation, the predominant lithologies are sandstones in metric beds or in lenses and layers of pelites (shales), deposited in an environment with deltas, tides, and storms. 4.4. Parecis Province 4.4.1. Xingu Sub-Basin The continental sediments of the Cretaceous Supersequence of the Parecis Basin, of interest to this study, made up of Salto das Nuvens Formation of the Upper Cretaceous that occurs in the escarpment of the Serra do Roncador, a region to the east of the Mato Grosso state. According to Pedreira et al. (2003), the Parecis Basin is of the IF-type (Interior Fracture) evolving to IS-type (Interior Sag). The Salto das Nuvens Formation is constituted by conglomerates and red immature sandstones with meddle to large-scale cross stratification, with intercalated lenses of reddish argillites and siltstones that are deposited in an aeolian fluvial environment (Costa et al., 1975). The Upper Cretaceous age is demonstrated by the presence of fossils, such as the Mesosuchidae (Notosuchidae). The Salto das Nuvens Formation is covered predominantly by sandy sedimentary rocks that are little consolidated and represented by sand, silt, clay, and gravel, called Ronuro Formation, associated to the Alto Xingu Sub-Basin and attributed to the Neogene age (Tertiary). 36 4.5. Carajás Province This Province was subdivided by Santos et al. (2000) and Santos (2003) into two distinct domains: Rio Maria (Mesoarchean) and Carajás (Neoarchean). The Rio Maria domain, located in the southern portion of the Amazon Craton, is the subject of this study 4.5.1. Rio Maria Domain The Rio Maria Domain is essentially constituted by granite-greenstone that represents two recognized periods of addition of youthful crust: between 3,05-2,96 Ga and 2,87-2,85 Ga. This domain corresponds to the greenstone belts grouped in the Andorinhas Supergroup (Souza et al. 2001). It is represented by the Lagoa Seca Group (metaturbidites and calc-alkaline volcanic rocks) and Babaçu Group (mafic and ultramafic volcanics). These units are cut by TTG intrusions (tonalite, trondhjemite, and granite) of the Caracol and Arco Verde types, with slightly younger ages between 2,924±2 Ma (Leite, 2001) and 2,957±21 Ma (Macambira and Lancelot, 1996), and represent primitive island arcs in the evolution of the region. The second association, according to Santos (2003), congregates the greenstone belts that consist of metasedimentary rocks (graywackes, turbidities, and iron formations) and a great volume of mafic and ultramafic volcanic rocks, common to the Tucumã and Gradaús groups, with an age of 2,868 ± 8 Ma (Avelar et al. 1999). TTG granitoids, for example, Trondhjemite Mogno and Parazônia Tonalite types present ages of 2,871 Ma and 2,858 Ma, respectively (Pimentel and Machado, 1994). The calc-alkaline rocks are predominantly granodiorites and monzogranites, for instance, Xinguara Granite and Rio Maria Granodiorite), generated between 2,87 and 2,85 Ga. 4.6. Central Amazon Province Santos et al. (2000) separated the Carajás Province from the Central Amazon Province based on differences in rock types and in structural trends. It was defined 37 previously as a single Archean province by Tassinari (1996), onto which several younger Proterozoic mobile belts were accreted. The basement rocks of the Amazon Central Province comprises of a poorly known basement (Santos, 2003). It is divided into two segments: the Mapuera– Tumucumaque rocks of the Guianense Complex represent the northern segment, while the Iriri-Xingu Domain of the Xingu Complex represents the south segment. The latter occurs in the study area. 4.6.1. Iriri-Xingu Domain The Archean basement of this domain is similar to a TTG association composed by granodioritic and tonalitic gneiss. This basement was metamorphosed into amphibolite facies attributed to the Xingu Complex that possess ages of 2,851 ± 4 Ma U-Pb in zircon (Machado et al., 1991). The Uruará Tonalite was studied by SHRIMP U-Pb and revealed an Archean crystallization age of 2,503 ± 10 Ma and a population inherited with 2,581 ± 6 Ma. However, part of those “complexes” was possibly formed in the Paleoproterozoic (Santos, 2003). The supracrustal rocks are represented by felsic to intermediate volcanics (Iriri Formation), A-Type granites (Maloquinha Intrusive Suite), with a sedimentary cover dominated by fluvial braided deposits (Gorotire Formation). The volcanics of the Iriri Formation and the granite of the Maloquinha Suite were generated by the Uatumã Magmatism (Santos and Reis Neto, 1982), evolving between 1,88 to 1,70 Ga. 5. REGIONAL TECTONIC SETTING OF DEFORMATION The South American Platform encompasses a succession of orogenic episodes involving crustal accretion and reworking which are intercalated by taphrogenic events dated from the Mesoarchean to the Neoproterozoic. The tectonic setting of the Brazilian Platform in the study area is characterized by two main orogenic cycles: Transamazonian (2.1 to 1.9 Ga) and Brasiliano (900 to 550 38 Ma). The first corresponds from Archean to Paleoproterozoic terrains of the Goiás Massif (greenstone belts and TTG terrains) generated between 2.8 and 2.7 Ga (Queiroz et al., 1999; Pimentel et al., 2000) and orthogneiss of the Porto Nacional-Nova Crixás Domain with a U-Pb SHRIMP age of 2.2 Ga (Fuck et al. 2001). These old terrains were affected by tectono-metamorphic events at 2.01 Ga (Transamazonian Cycle) and subsequently deformed with shear zones from 590 to 551 Ma (Brasiliano Cycle). The second younger cycle (Neoproterozoic) comprises the Brasiliano Orogenic System that is constituted by the Goiás Magmatic arc (Mara Rosa-Arenópolis intra-oceanic arcs), and Araguaia and Paraguay belts. The regional structural picture consists of ancient collisions of several continental blocks which are limited by major crustal sutures in association with transcurrent shear belts and thrust faults. Although the region represents a continental crust that is relatively stable and has strain rates that are believed to be low, the majority of faults which show evidence for neotectonic movement are related to crustal discontinuities of Precambrian or Paleozoic heritage. 5.1. Evidences of the different tectonic movements The expressive occurrences of rocks with ages that vary from the Archean to the Quaternary, deformed, in the majority of cases, in consequence of several tectonic cycles that acted in the region shows a complex deformation geometry. For the knowledge and extraction of lineaments, the criteria are the expressions of the linear elements of the relief, such as crest segment lines, elongated depressions, rectilinear lake and drainage patterns, vegetation belts, linear variation of soil tonality, and so forth. Fractures (including faults, shear zones, and joints) in the terrestrial crust affect the topography or the features of the land in some way. The various linear elements that exist in nearly all landscapes are controlled by subsurface tectonics and can significantly affect morphology and hydrology temporarily or permanently by triggering avulsions. In order to represent and classify variations in the orientation of the structural lineaments, rose diagrams were constructed. The diagrams show the variations of the 39 orientation grouped in classes, according to the frequency of occurrence in determined trends. The extraction of the lineaments was obtained from field data, remote sensing products (Landsat ETM and SRTM) and aerogeophysical (magnetometry and gamma- ray spectrometry) data. Three main shear zone trends were distinguished: N20-40E, N50-60W and N15-30W (Fig. 4). Fig. 4. Rose diagrams of structural lineaments of the main tectonic domains. PN/NC- Porto Nacional-Nova Crixás Domain, MRA-Mara Rosa Arc (Goiás Magmatic Arc), BB-Bananal Basin, AB-Araguaia Belt, AA-Arenópolis Arc (Goiás Magmatic Arc), PP-Paraná Province, RM/IX-Rio Maria/Iriri-Xingu Domains (Amazon Craton) and GM-Goiás Massif. The first, the dextral N20-40E-trending shear zone, is called Transbrasiliano Lineament (Schobbenhaus et al., 1975). It is characterized by a strike-slip fault system of high angle associated to transpressional and transtensional regimes of nature, predominantly ductile-brittle and brittle. The deformation geometry is compatible with the Riedel model, with a compressive effort from west for east (direction of σ1). This deformation of continental dimension is recorded at almost all the geological provinces, with greater evidence in PN/NC (Porto Nacional-Nova Crixás), MRA (Mara Rosa Arc), and in the south segment of the AB (Araguaia Belt). This shear zone exerts strong control into the plutonism/volcanism, sedimentation/erosion, and deformational aspects during the geological and geomorphologic evolutions. 40 The second is a sinistral N50-60W shear zone trend. In the northern part of the Araguaia Belt there are compressive and tangential efforts, directed westwards against the Rio Maria Domain (Amazon Craton). The compressive regime developed displacement surfaces and a shear zone of low angle (thrust fault) with a N-S trend that is cut by sinistral shear zones trend with around N50W, both in AB (Araguaia Belt) and in RM/IX (Rio Maria and Iriri-Xingu domains). The southern segment of the Araguaia Belt is transposed by the N30-40E shear zone trend of the Transbrasiliano System. The third, sinistral N15W to N30W-trending shear zone is sub-parallel to Anápolis-Itauçu Granulitic Belt that occurs in the south of Goiás state. This fault system represents a progressive deformation, with tectonic transport from west to east against the São Francisco Craton. This tectonic stress was responsible for the development of an extensive shear zone with ductile and ductile-brittle regimes that deformed rocks both in infrastructure as in suprastructure. The sinistral N15W to N30W shear zone trend is represented in domains of AA (Arenópolis Arc) and GM (Goiás Massif). However, this fault system occurs in PP (Paraná Province) as a reactivation of old basement faults. 5.1.1. Neotectonic Faulting Neotectonics is the study of young tectonic events that occurred or are still occurring in a given region, after its orogenesis or after the most significant tectonic readjustment (Pavlides, 1989). Hasui (1990) used the term ‘resurgent tectonics’ for the reactivation of Precambrian faults during the Cenozoic. This author relates the origin of neotectonism in Brazil to the migration of the South American continent and consequent opening of the South Atlantic, whose movements occur until the present day. Tectonically active areas have a direct relation between natural seismicity and neotectonism (Hasui and Ponçano, 1978; Schumm et al., 2000; Oswald and Wesnousky, 2002; Goodbred Jr. et al., 2003). 41 In this context, there are some localities in Brazil with concentration of seismic activity, named seismotectonic provinces, for example, Fortaleza and São Francisco Craton seismogenic zone, in the Northeast; Mantiqueira and Serra do Mar seismogenic zone, in the Southeast; and Goiás-Tocantins seismogenic zone, in the central region of the country (Ferreira and Assumpção, 1983; Hasui, 1990; Riccomini, 1990; Bezerra, 1999). Seismogenic zones in Brazil are invariably associated with the regions where Precambrian geossuture reactivations occur. Those reactivations would occur owing to epirogenetic movements since the end of the Cretaceous to the Pleistocene. According to Hasui et al. (1978), the continental taphrogenic basins of the Brazilian Southeast developed since the Brasiliano Cycle (Upper Proterozoic) and culminated with the implementation of continental basins in the Late Tertiary and/or Pleistocene by the reactivation of old faults. The main seismogenic area of Central Brazil, the object of this study, is located between the Amazon and São Francisco cratons, being the interaction between them the main responsible for significant neotectonic and seismic activities in the area, called Goiás-Tocantins Seismogenic Zone (GTSZ). In the region there are several seismic activities, with a magnitude that ranges from 2,9 to 4,1 (Richter scales) along the NE-SE trend (Transbrasiliano Lineament); its dimensions are 700km long and 200km wide (Veloso, 1997), originated on continental tectonic structures. Fig. 5 shows the regional epicenter distribution in the GTSZ. This suture zone evolved to frontal, oblique and directional ramps, which placed the high-grade terrain (Porangatu Granulitic Complex) on one side and metavolcano- sedimentary belts on the other. In this context, there is the Água Bonita Graben (Silurian/Devonian) limited by faults of the Transbrasiliano Lineaments. Evidences of this tectonic regime were presented by Hales (1981) from geophysical data (magnetometry and seismics) carried out in the Middle Araguaia River region, between the south of Bananal Island and the confluence of the Araguaia- Crixás rivers. This author stated that the Bananal Basin finds itself structured in horst and graben systems with a predominance of NE-SW trend faulting (Figure 6). 42 In this sense, Rabelo and Soares (1999) described an active NE fault zone that crosses the central Pantanal Basin, in Mato Grosso state, related to the reactivation of the Transbrasiliano Lineament, in the basement. The northern border of the Paraná Basin and the Bananal Basin were affected by faulting that was reactivated by the Arenópolis Magmatic Arc basement (Fig. 7). Fig. 5. Relation between seismic activity and magnetic lineaments along Goiás- Tocantins Seismogenic Zone (GTSZ) in the Upper and Middle Araguaia River Basin. Seismic data are from the Seismological Observatory of the University of Brasília. The magnetic anomaly image is a total field reduced from IGRF (International Geomagnetic Reference Field), generated from Aero database of Geological Survey of Brazil. The area of the rectangle in the image corresponds to Fig. 6. 43 Fig. 6. Faulting system in horst and graben in the Bananal Basin interpreted from magnetometric data (modified from Hales (1981). SRTM 3D shaded relief image. Therefore, tectonic features of the basement influenced the development of the major Brazilian Phanerozoic interior basins. These basins are result from the extensional regime of Neoproterozoic transcurrent fault lines, reactivated by neotectonic processes during the fracturing of the Gondwana. For example, there are the Cenozoic intracratonic basins of Central Brazil (Bananal and Pantanal), Southeast Brazil (Volta Redonda, Resende, Taubaté, São Paulo, Curitiba), and Paleozoic rift and strike-slip basins of Northeast Brazil (Recôncavo, Tucano, Jatobá, Araripe, Iguatu, Rio do Peixe). Surely, the multidisciplinary study that involves neotectonic features such as fault kinematics, geochronological dating, morphogenesis, areas of erosion and sedimentation, seismicity, intraplate tensions, source, and thermal flow. These researches will allow the necessary knowledge of the phenomena and of the 44 geological-tectonic processes in regional and global scales of Central Brazil. Such information is still quite scarce. Fig. 7 – Fault of the Transbrasiliano Lineament System cutting rocks of the Quaternary (Bananal Basin), Devonian (Paraná Basin) and Neoproterozoic basement (Arenópolis Magmatic Arc). 6. TECTONO-GEOLOGICAL EVOLUTION The Structural Provinces of the study area in the context of the South American Platform have a complex composition, reflecting a polycyclic history of its basement, and varying from the Mesoarchean (3.0-2.8 Ga) to the Cambrian/Ordovician (500-480 Ma). Paraná and Parnaíba Province basins (Paleozoic/Mesozoic) and Bananal Basin (Pleistocene) dominantly represent Phanerozoic sedimentary covers. Archean units are constituted by TTG (tonalite, trondhjemite, and granite) blocks of continental crust (Goiás-Crixás and granitoids of the Vila Maria Domain) which 45 evolved in successive episodes of crustal accretion that were associated with several greenstone belts; these were generated in an extensional-oceanic environment. The Paleoproterozoic comprises mostly TTG terrains (Xingu Complex) with felsic to intermediate volcanic rocks (Xingu-Iriri Domain) and granite-gneissic terrains (Porto Nacional-Nova Crixás Domain) which were generated during the Trans- Amazonian orogenic Cycle (2.25-2.01 Ga). The abortion of the Statherian Taphogenesis, outside the area (Serra da Mesa-Araí groups), originated expansion in the Mesoproterozoic between the Calymmian and Ectasian (1.6-1.2 Ga) of ample syneclises with sedimentary deposits of marine and transitional environments that encompass the Rift Basin of the Serra Dourada Group. The last orogenic collage in the area corresponds to the Brasiliano Orogenic System and comprises a series of intra-oceanic magmatic arcs. Three large-scale episodes have been defined (Pimentel et al. 1999, Silva et al., 2000; Delgado et al., 2003): (i) Brasiliano Orogenic System I (900-700 Ma) consists of the Arenópolis- Anicuns-Itaberaí-Mara Rosa arcs with a collisional peak at 790 Ma; (ii) Brasiliano Orogenic System II (640-610 Ma) with the Jaupaci-Iporá-Amorinópolis magmatic arcs and Araguaia and Paraguay belts, as well as sedimentary rocks which are deposited in a foreland basin (Alto Paraguay). It is the main orogenic episode of the Brasiliano collage, characterized by juvenile accretion with a metamorphic peak at 632 Ma; (iii) Brasiliano Orogenic System III (600-520 Ma) comprises the most recent system of orogens which marks the transition to a stable environment in the South American Platform at ca. 520 Ma. The deformation style with thrust and fold belts associated to the strike-slip fault system is dominant in Neoproterozoic rocks of the Tocantins Province. The first two systems are associated with the metasedimentary rocks with N-S trend (Araguaia Belt) and N70E trend (Paraguay Belt and Foreland Basin). Sinistral transcurrent faults around N50W control the structuring of the Archean terrains (Goiás Massif, Rio Maria, and Xingu-Iriri Domains) and the southern segment of the Neoproterozoic Goiás Magmatic Arc (Arenópolis Arc). The dextral N20-40E-trending shear zone has a ductile-brittle and brittle nature with a tensional fracture around 90º direction for σ1. This faulting presents verticalized 46 plans and horizontal to sub-horizontal relative movements. It constitutes the orientation of the main shear zone of the study area and corresponds to the Transbrasiliano Lineament of continental dimension that extends 2,700km in Brazilian territory, revealing continuity in the oceanic fracture zones such as the Patos and Pernambuco lineaments. This shear zone has registers at almost all the geological provinces, with greater evidence in the south portion of the Araguaia Belt, in Porto Nacional-Nova Crixás Domain and Mara Rosa Magmatic Arc (Figs. 2 and 4). These shear zone directions represent crustal weakness zones that were reactivated during the Phanerozoic time. The beginning of the Mesozoic, from a tectonic point of view, represents a continuation of the conditions prevailing during the Paleozoic that was called Intracratonic Cycle by Sampaio and Northfleet (1973). In Paleozoic, the Brazilian structures were active from the Cambro-Ordovician in an extensive regime of the IF-type (Interior Fracture) with implantation of grabens that originated from the sedimentary deposits of the Parnaíba and Paraná Provinces. The shapes of the intracratonic sedimentary basins, e.g. the Paraná and Parnaíba provinces seem to be controlled by the N20-40E (Transbrasiliano Lineament), N50-60W, and around N-S-trending Precambrian structures. The Parnaíba Province consists of four successive basins: IF-type Jaibara Graben and others (Cambro-Ordovician); IS-type Parnaíba Basin (Silurian-Triassic) has marine, fluvial-deltaic and desertic environments; IF-type Alpercatas Basin (Jurassic-Cretaceous) is essentially continental with fluvial-lacustrine and eolian deposits and basaltic flows; IS/MS-type Grajaú Basin (Cretaceous) has both sedimentary rocks that were deposited in closed marine environments and eolian deposits. On the other hand, the Paraná Province encompasses three successive basins: MSIS-type Paraná Basin (Devonian) presents marine and fluvial deposits; IF-type Serra Geral Basin (Jurassic-Eo-Cretaceous) was deposited in marine, fluvial, and desertic environments with glacial incursions and continental flood basalts; IS-type Bauru Basin (Upper Cretaceous) presents two phases of deposition: the first is essentially desertic and the second is of a fluvial-eolian environment. 47 In Quaternary time, the Bananal Basin developed due to the reactivation of the Transbrasiliano structures in horst and graben, according to geophysical studies presented by Hales (1981). Recent apatite fission-track dating suggests an increase in the rate of crustal uplift after the Pliocene (Saadi et al., 2002). Thermoluminiscence (TL) and Optically Stimulated Luminescence (OSL) chronologies accomplished in the sandy sediments of the Araguaia Formation showed that the river avulsion events occurred in Upper Pleistocene from 26.4±3.1 to 17.2±2.3 ka BP and in Middle Pleniglacial from 56.6±5.9 to 34.0±4.6 ka BP. In addition, the fluvial aggradation of the Araguaia Formation sediments was dominant during the Middle and Upper Pleistocene, between 240.0±29.0 and 17.2±2.3 ka BP (Valente and Latrubesse, 2007). 7. CONCLUSIONS The Araguaia River Basin occupies an area of 384,600 km² on a complex geological environment, reflecting its basement’s tectonics and metamorphic polycyclic history. This Precambrian infracrust, with 45% of the Araguaia River Basin, consists of rocks with composition and age very diversified: a) Mesoarchean TTG (tonalite, trondhjemite and, granodiorite) terrains and greenstone belts (Goiás Massif and Rio Maria); b) Paleoproterozoic granitic-gneiss and metavolcano- sedimentary rocks (Porto Nacional-Nova Crixás, Iriri-Xingu, and Rift Basin), and c) widespread Neoproterozoic metamorphic folded belts (Goiás Magmatic arcs, Araguaia and Paraguay belts, and Foreland Basin). The supracrustal domain which covers 55% of the area encompasses the intracratonic sedimentary basins generated during the Paleozoic/Mesozoic (Paraná, Parnaíba and Parecis provinces and Água Bonita Basin) and in the Quaternary (Bananal Basin). Basement rocks were affected by three tectono-metamorphic events which correspond to Jequié (~2.7 Ga), Transamazonian (~2.0 Ga), and Brasiliano (900-520 Ma) orogenic cycles. The Brasiliano event is the most widespread and consists of three large-scale tectonic episodes: Brasiliano I (900-700 Ma), Brasiliano II (640-610 Ma), and Brasiliano III (600-520 Ma). These Brasiliano systems are characterized by collision-related orogens associated to a displacement of surfaces and thrust faults of 48 low angle (frontal ramps of N-S direction) and an expressive strike-slip fault system with N30-40E trend of high angle, called Transbrasiliano Lineament. The latter is associated to transpressional and transtensional regimes of a ductile-brittle and brittle nature. These strike-slip fault systems and thrust fault belts involve both the supracrust and the infracrust and are related to important magnetic lineaments in the region. The Transbrasiliano Lineaments have a transgondwanic extension and constitutes the most important dextral strike-slip fault zone of Central Brazil. The Precambrian fault systems are crustal weakness zones that were reactivated during the Phanerozoic with directional, uplift, and subsidence movements, generating expressive taphrogenic events represented by Paleozoic/Mesozoic and Quaternary intracratonic basins. These basins were influenced by the geodynamics of the Gondwana. The faults of the neotectonic events cut both the Precambrian basement and Quaternary sedimentary rocks. These deformational processes generated a deep imbalance in the hydrologic and fluvial sedimentary systems of the region with the development of innumerable river avulsion points, abandoned channels, and underfit rivers, where radiometric dating (TL and OSL) the sandy fluvial sediments showed that river channel avulsions were more active in the Middle and Upper Pleniglacial. The Araguaia River Basin contains several tectonic and geological environments with high potentiality for important econ