Proveniência e Intemperismo da Formação São Carlos, Cretáceo Superior, e significado tectônico na borda leste da Bacia Bauru, SE Brasil

Geochemistry of major and trace elements has been used as an important tool for the study of provenance and tectonic and climatic evolution of sedimentary basins. The São Carlos Formation is an Upper Cretaceous unit that lies on the eastern border of the Bauru Basin. Despite the paleontological and paleodepositional studies performed in this unit in the last years, little is known about the correspondence between tectonic and climatic conditions acting during the first stages of sedimentation. The hypothesis of this paper is to evaluate São Carlos and Araçatuba formations and understand the evolution of the eastern border of the basin. Thus, were conducted geochemical studies using X-ray fluorescence on sandstones, siltstones, and shales from the São Carlos Formation. According to the chemical weathering index, which presented values ranging from 57.12 to 71.58%, the oxides of major elements indicate that moderate weathering processes affected the source area, possibly associated with the arid-semiarid climate. Alkaline rocks, granites, gneisses, and metasediments were the main lithotypes of the source area. Ternary diagrams show that the tectonic environment was equivalent to the passive continental margin, coinciding with the Serra do Mar and, secondarily, Alto Paranaíba Uplift regions. Based on major and trace elements, their ratios, and published data on the basin, was elaborated a paleogeographic model of the eastern border of the Bauru Basin, concluding that the source area of the sediments was constituted by intermediate and felsic rocks, sometimes recycled by sedimentary processes1937794FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP2015/17632-5A geoquímica dos elementos maiores e traço tem sido usada como importante ferramenta para o estudo da proveniência, evolução tectônica e climática das bacias sedimentares. A Formação de São Carlos é uma unidade do Cretáceo Superior que ocorre na borda leste da Bacia Bauru. Apesar dos estudos paleontológicos e paleodeposicionais realizados nesta unidade nos últimos anos, pouco se sabe sobre as condições tectônicas e climáticas que atuam nos primeiros estágios da sedimentação, bem como, sua relação estratigráfica com outras unidades da bacia. A hipótese deste trabalho consiste em avaliar se as formações São Carlos e Araçatuba possuem correspondência e compreender a evolução da margem leste da bacia. Dessa forma, realizaram-se estudos geoquímicos utilizando Fluorescência de Raios-X em arenitos, siltitos e folhelhos da Formação São Carlos. Através do uso do índice de intemperismo químico, os óxidos dos elementos maiores indicam que, com valores entre 57,12 e 71,58%, os processos de intemperismo moderados, possivelmente associados ao clima árido-semiárido, afetaram a área de origem. Rochas alcalinas, granitos, gnaisses e metassedimentos foram os principais litotipos da área fonte. Os diagramas ternários indicam que o ambiente tectônico era equivalente à margem continental passiva, coincidindo com as regiões da Serra do Mar e, em segundo lugar, Soerguimento Alto Paranaíba. Com base nos elementos maiores e traços, suas razões, e dados já publicados da bacia, foi elaborado um modelo paleogeográfico da borda leste da Bacia Bauru, concluindo-se que a área de origem dos sedimentos foi constituída por rochas intermediárias e félsicas, às vezes recicladas por processos sedimentare

Provenance and weathering index of the Upper Cretaceous São Carlos Formation and its tectonic significance in the eastern Bauru Basin, SE Brazil

A geoquímica dos elementos maiores e traço tem sido usada como importante ferramenta para o estudo da proveniência, evolução tectônica e climática das bacias sedimentares. A Formação de São Carlos é uma unidade do Cretáceo Superior que ocorre na borda leste da Bacia Bauru. Apesar dos estudos paleontológicos e paleodeposicionais realizados nesta unidade nos últimos anos, pouco se sabe sobre as condições tectônicas e climáticas que atuam nos primeiros estágios da sedimentação, bem como, sua relação estratigráfica com outras unidades da bacia. A hipótese deste trabalho consiste em avaliar se as formações São Carlos e Araçatuba possuem correspondência e compreender a evolução da margem leste da bacia. Dessa forma, realizaram-se estudos geoquímicos utilizando Fluorescência de Raios-X em arenitos, siltitos e folhelhos da Formação São Carlos. Através do uso do índice de intemperismo químico, os óxidos dos elementos maiores indicam que, com valores entre 57,12 e 71,58%, os processos de intemperismo moderados, possivelmente associados ao clima árido-semiárido, afetaram a área de origem. Rochas alcalinas, granitos, gnaisses e metassedimentos foram os principais litotipos da área fonte. Os diagramas ternários indicam que o ambiente tectônico era equivalente à margem continental passiva, coincidindo com as regiões da Serra do Mar e, em segundo lugar, Soerguimento Alto Paranaíba. Com base nos elementos maiores e traços, suas razões, e dados já publicados da bacia, foi elaborado um modelo paleogeográfico da borda leste da Bacia Bauru, concluindo-se que a área de origem dos sedimentos foi constituída por rochas intermediárias e félsicas, às vezes recicladas por processos sedimentares.Geochemistry of major and trace elements has been used as an important tool for the study of provenance and tectonic and climatic evolution of sedimentary basins. The São Carlos Formation is an Upper Cretaceous unit that lies on the eastern border of the Bauru Basin. Despite the paleontological and paleodepositional studies performed in this unit in the last years, little is known about the correspondence between tectonic and climatic conditions acting during the first stages of sedimentation. The hypothesis of this paper is to evaluate São Carlos and Araçatuba formations and understand the evolution of the eastern border of the basin. Thus, were conducted geochemical studies using X-ray fluorescence on sandstones, siltstones, and shales from the São Carlos Formation. According to the chemical weathering index, which presented values ranging from 57.12 to 71.58%, the oxides of major elements indicate that moderate weathering processes affected the source area, possibly associated with the arid-semiarid climate. Alkaline rocks, granites, gneisses, and metasediments were the main lithotypes of the source area. Ternary diagrams show that the tectonic environment was equivalent to the passive continental margin, coinciding with the Serra do Mar and, secondarily, Alto Paranaíba Uplift regions. Based on major and trace elements, their ratios, and published data on the basin, was elaborated a paleogeographic model of the eastern border of the Bauru Basin, concluding that the source area of the sediments was constituted by intermediate and felsic rocks, sometimes recycled by sedimentary processes

SOURCE - AREA, PALEOWEATHERING AND PROVENANCE OF THE LATE CRETACEOUS SEQUENCES OF THE BAURU BASIN (SE BRAZIL)

Geochemical and mineralogical analyses of sandstones and mudstones from the Bauru Basin (SE Brazil) were undertaken to determine the provenance, tectonic setting and weathering during the Late Cretaceous. X-ray diffraction (XRD) analysis indicate that samples comprise of quartz, microcline and hematite. Illite, montmorillonite and palygorskite are the main clay minerals. X-ray fluorescence (XRF) and inductively coupled plasma mass spectrometry (ICP-MS) analyses determined the main chemical composition of the rocks from the Bauru Basin. Predominant major elements include SiO2, Al2O3, Fe2O3, MgO, K2O and TiO2, and were used to determine the rock composition and classify them as Fe-sands, litharenites, sublitharenites, wackes and shales. Trace elements, including the rare earth elements and the ratios among them determined the source area and its tectonic setting. A correlation matrix including major and trace elements and plots of major and trace elements and values for the ratios such as La/Sc (1.47-4.86), (La/Yb)c (3.86-20.44) and the Eu anomaly (Eu/Eu*= 0.62-0.92), compared to data from the literature indicate the source rock is associated with a continental passive margin tectonic setting. The sedimentary succession of the Bauru Basin derived from quartzitic to granitic-gneissic rocks of stable continental areas. Chemical Index of Alteration (CIA) and Chemical Index of Weathering (CIW) values range, respectively, from 64.83 to 92.3 and 84 to 98.2, indicating a moderate to intense weathering in the source area in a semiarid climate conditions.Estudos geoquímicos e mineralógicos de arenitos e argilitos da Bacia Bauru (Cretáceo Superior), localizada na região Sudeste do Brasil foram realizados visando à determinação da proveniência, tectônica da rocha fonte, o papel de processos como intemperismo e reciclagem sedimentar na assinatura geoquímica da rocha fonte e uma evolução paleoambiental para a área de estudo. As amostras têm sua mineralogia principal composta por quartzo, microclínio, calcita, albita, dolomita e hematita. Illita, montmorillonita e paligorsquita são os argilominerais identificados. Elementos maiores, traços e terras raras e as razões elementais entre eles foram utilizadas para determinar a composição da rocha fonte. Valores do Índice Químico de Alteração e do Índice de Intemperismo Químico variando de 64 a 92 e de 84 a 98, respectivamente, e a ocorrência de feldspatos nas rochas sedimentares indicam intemperismo moderado na área fonte. Gráficos de elementos maiores e traços e valores para razões como La/Sc (1,47-4,86), (La/Yb)c (3,86-20,44) e a anomalia de Eu (Eu/Eu* = 0,62-0,92) comparados com dados da literatura sugerem que os sedimentos da Bacia Bauru na área de estudo tenham sido originados de rochas de composição quartzítica a granítico-gnáissica, derivadas de áreas continentais estáveis e depositados em ambientes de bacias intracratônica. A possível área-fonte para as rochas estudadas localiza-se a NE da Bacia Bauru, consistindo em rochas graníticas e metassedimentares do embasamento pré-cambriano. A deposição sedimentar na Bacia Bauru reflete a interação de processos aluviais e lacustres

Mineralogia de paleossolos da Formação Marília e seu significado na evolução ambiental do Maastrichtiano da Bacia Bauru, sudeste do Brasil

Soils and paleosols reflect the complex interplay between sedimentation, erosion and non-deposition. An analysis of the mineralogical components of paleosols is critical for the reconstitution of the factors, processes and environments in which they were formed. The recognition of mineralogical assemblages can reveal the environmental conditions during pedogenesis and through quantitative analysis it is possible to identify a vertical variation in mineral concentration or leaching over the paleosol profiles, indirectly pointing to environmental processes that dominated during the pedogenetic evolution. The objective of this study is to discuss the significance of mineral phases and to quantify the environmental evolution and degree of development of paleosols of the Marília Formation, Maastrichtian of Bauru Basin. Three sections have been described (A1, A2, A3) in the Marília Formation. The mineralogy was determined by x-ray diffraction, and mineral quantification was obtained through the Rietveld refinement method. The calcretes of the Marília Formation are pedogenic, mostly authigenic minerals. The variation of quartz, calcite, palygorskite and smectite, the micromorphology, and the diversity of subsurface horizons (Bkm, Btkm, Bt) indicate that the studied paleosols did develop in semi-arid conditions, with episodes of higher rainfall rates, humidity, leaching and desilication47340342

Pedodiagenetic Characterization of Cretaceous Paleosols in Southwest Minas Gerais, Brazil

The influence of post-burial geological processes on preserving pedogenic properties has great importance in identifying ancient paleosols both in the field and in a laboratory. However there are not many publications that focus on characterizing paleosol diagenesis. As temperature and pressure progressively increase, evidence of pedogenesis is modified and destroyed, hindering paleoenvironment characterization and interpretation. This paper discusses diagenetic evidence and its relation to strictly pedogenic features, like structure, cements, nodules, and neoformation of clay minerals using the carbonate paleosols of the Marilia Formation in the upper unit of the Bauru Basin as a case study. Despite the long geotectonic and thermal history of the Marilia Fomation, paleosols bring us pedogenic evidence that can undergo micromorphological analyses, such as cementation, clay illuviation, bioturbation, and ped structures. The results of analyses in 25 paleopedogenic horizons indicate that the paleotopographic features were responsible for distribution of the diagenetic processes and preservation of the paleosol properties. The maturity of those paleosols controls lithification. In mature paleosols that developed in more stable portions of the landscape, characteristics such as carbonate cementation and development of pedogenic structures are the main factors that inhibit diagenesis. However diagenetic processes that influence poorly-developed paleosols are controlled by depositional characteristics and by changes in the water table, enabling more advanced diagenetic processes, compared to mature paleosols.The influence of post-burial geological processes on preserving pedogenic properties has great importance in identifying ancient paleosols both in the field and in a laboratory. However there are not many publications that focus on characterizing paleosol diagenesis. As temperature and pressure progressively increase, evidence of pedogenesis is modified and destroyed, hindering paleoenvironment characterization and interpretation. This paper discusses diagenetic evidence and its relation to strictly pedogenic features, like structure, cements, nodules, and neoformation of clay minerals using the carbonate paleosols of the Marília Formation in the upper unit of the Bauru Basin as a case study. Despite the long geotectonic and thermal history of the Marília Fomation, paleosols bring us pedogenic evidence that can undergo micromorphological analyses, such as cementation, clay illuviation, bioturbation, and ped structures. The results of analyses in 25 paleopedogenic horizons indicate that the paleotopographic features were responsible for distribution of the diagenetic processes and preservation of the paleosol properties. The maturity of those paleosols controls lithification. In mature paleosols that developed in more stable portions of the landscape, characteristics such as carbonate cementation and development of pedogenic structures are the main factors that inhibit diagenesis. However diagenetic processes that influence poorly-developed paleosols are controlled by depositional characteristics and by changes in the water table, enabling more advanced diagenetic processes, compared to mature paleosols4111

Micromorphology of Paleosols of the Marília Formation and their Significance in the Paleoenvironmental Evolution of the Bauru Basin, Upper Cretaceous, Southeastern Brazil

Deduction of associated paleoenvironments and paleoclimate, definition of the chronosequence of paleosols, and paleogeographic reconstruction have become possible through the application of micromorphology in paleopedology. Micromorphology has also been useful in recognition of weathering processes and definition of minerals formed in succession. In this respect, the objective of this study was to identify the development of pedogenic processes and discuss their significance in the paleoclimate evolution of the Marília Formation (Maastrichtian) of Bauru Basin. Three sections of the Marília Formation (A1, A2, and A3) were described, comprising nine profiles. Micromorphologic al analysis was carried out according to the specialized literature. In the Marília Formation, the paleosols developed in sandstones have argillic (Btkm, Bt) and carbonate (Bk) horizons with different degrees of cementation, forming mainly calcretes. The evolution of pedogenic processes, in light of micromorphological analysis, evidenced three moments or stages for the genesis of paleosols with Bkm, Btk, and Bt horizons, respectively. In the Maastrichtian in the Bauru Basin, the paleosols with Bkm are older and more arid environments, and those with Bt were formed in wetter weather, but not enough to lead to the genesis of enaulic-related distributions, typical of current Oxisols.Deduction of associated paleoenvironments and paleoclimate, definition of the chronosequence of paleosols, and paleogeographic reconstruction have become possible through the application of micromorphology in paleopedology. Micromorphology has also been useful in recognition of weathering processes and definition of minerals formed in succession. In this respect, the objective of this study was to identify the development of pedogenic processes and discuss their significance in the paleoclimate evolution of the Marília Formation (Maastrichtian) of Bauru Basin. Three sections of the Marília Formation (A1, A2, and A3) were described, comprising nine profiles. Micromorphologic al analysis was carried out according to the specialized literature. In the Marília Formation, the paleosols developed in sandstones have argillic (Btkm, Bt) and carbonate (Bk) horizons with different degrees of cementation, forming mainly calcretes. The evolution of pedogenic processes, in light of micromorphological analysis, evidenced three moments or stages for the genesis of paleosols with Bkm, Btk, and Bt horizons, respectively. In the Maastrichtian in the Bauru Basin, the paleosols with Bkm are older and more arid environments, and those with Bt were formed in wetter weather, but not enough to lead to the genesis of enaulic-related distributions, typical of current Oxisols4112

PALEOPRECIPITATION CHANGES BASED ON PALEOSOLS PROFILES OF THE MARÍLIA FORMATION (UPPER CRETACEOUS) IN THE EASTERN PORTION OF THE BAURU BASIN IN SOUTHEASTERN BRAZIL

The Marília Formation is a Maastrichtian sequence of the Bauru Basin that crops out in the Southeastern Brazil. This formation consists of an illuvial deposits succession characterized by alternating sedimentary strata and paleosols. Pedogenic features related to climatic factors can be used as a tool for the interpretation of paleoenvironments. Through macro- and microscopic descriptions, mineralogical analysis and geochemical data, twenty paleosol sections were identified and characterized in the Marília Formation. The characterization of C, Ck, Bt, Btk and Gley horizons and the geochemical data allowed the identification of paleoclimatic factors influencing the formation of paleosols. Changes in the formation processes of these paleosols were mainly triggered by moisture variations. Paleoprecipitation estimates (MAP) obtained from CIA-K values in Bt and Btk horizons indicate that the precipitation rates varied from 20 to 1000 mm/year. These contrasting climatic conditions caused the overlap of distinct paleosol profiles, suggesting oscillation between arid to semi-arid conditions. The results from this work contribute to a better understanding of the Upper Cretaceous paleoclimatic in the Southeastern Brazil

AMBIENTES DEPOSICIONAIS E EVOLUÇÃO ESTRATIGRÁFICA DO CRETÁCEO SUPERIOR DA BACIA DOS PARECIS

Embora haja muitas publicações sobre as bacias cretácicas brasileiras, o entendimento sobre processos tectônicos e climáticos envolvidos na evolução das sequências continentais ainda carece de estudos, sobretudo aqueles relacionados à porção centro-oeste do país. A sequência sedimentar do Cretáceo Superior da Bacia dos Parecis, se assenta discordantemente sobre rochas vulcânicas das formações Anarí e Tapirapuã (Jurássico Inferior) e arenitos do Cretáceo Inferior da Formação Rio Ávila. É constituída por uma sucessão de estratos conglomeráticos e arenosos na base (Formação Salto das Nuvens) sobreposta por estratos arenosos no topo (Formação Utiariti). A partir da análise de fácies e arquitetura estratigráfica, foi elaborado um modelo paleoambiental e uma proposta de evolução que contempla aspectos tectônicos e climáticos dessa porção brasileira. Usando o conceito de nível de base estratigráfico e/ou a razão entre espaço de acomodação e suprimento sedimentar (A/S), foi identificado o padrão de empilhamento aluvial e eólico, que corresponde aos diferentes estágios da Tectônica Juruá. Os eventos de sedimentação que deram origem a sequência tiveram início após a gênese de uma discordância regional (Discordância K-1) entre o Cretáceo Precoce e Tardio. Durante o Cretáceo Tardio a Bacia dos Parecis abrigou um ciclo de sedimentação aluvial (Sequência 1A) e outro eólico (Sequência 1B). O primeiro registra o aumento na razão A/S onde se desenvolveram sistemas de leques retrabalhados por rios entrelaçados e dunas eólicas baixas (Trato de Sistema de Alta Acomodação – HST). Progressivamente o espaço de acomodação foi diminuindo, fazendo com que os depósitos aluviais fossem colmatados por campos de dunas (Trato de Sistema de Baixa Acomodação – LST). Nesse período a razão A/S tendeu a 1, chegando a ser negativa nos estágios finais, com possível by-pass sedimentar e gênese da Discordância K-2. A variação de fácies da base para o topo registra mudança nas condições de climáticas da bacia, passando de um ambiente mais úmido para mais seco. Dados de paleocorrentes indicam que o Alto de Tapajós ao norte da bacia esteve ativo, sendo a área fonte dos sedimentos

CARACTERIZAÇÃO GEOLÓGICA, MINERALÓGICA, QUÍMICA E CERÂMICA DA FORMAÇÃO CORUMBATAÍ NOS MUNICÍPIOS DE TAMBAÚ, PORTO FERREIRA E SANTA ROSA DO VITERBO - SP, VISANDO APLICAÇÃO E DIVERSIFICAÇÃO DE PRODUTOS NO POLO CERÂMICO DE SANTA GERTRUDES

O trabalho apresenta resultados do estudo da Formação Corumbataí nos municípios de Tambaú, Porto Ferreira e Santa Rosa do Viterbo no Estado de São Paulo, do ponto de vista geológico, químico, mineralógico e cerâmico, com o objetivo de conhecer as reservas existentes desta unidade geológica nesta região como fonte de matéria-prima cerâmica, buscando a melhora na qualidade e diversificação dos produtos fabricados no Polo Cerâmico de Santa Gertrudes. Inicialmente foram levantadas seções geológicas nas minerações existentes com o intuito de identificar as principais litofácies geológicas. De acordo com os levantamentos geológicos, as argilas da Formação Corumbataí são representadas pelas litofácies maciça - LM, laminada-LL, intercalada-LI e alterada-LA. A mineralogia identificada por DRX (fração total