Estimates of the depth and variation of lateritic weathering profiles are especially important in tropical areas such as Oahu, HI. Shear-wave velocity data were obtained by a new application of Multi-channel Analysis of Surface Waves (MASW) to map the base of the critical zone, to show variations in the LWP, and to derive weathering rates. The MASW technique proved highly capable of imaging the base of the critical zone, confirmed by lithological well data and direct field measurements. Profile thickness can be obtained without drilling, which has applications in engineering and geochemical studies. The measured rate of advance of the weathering front derived from the thickness measured by MASW ranged from 0.019 m/ka to 0.30 m/ka in mesic zones; about 1500 mm of annual rainfall, while a zone of 800 mm of annual rain fall revealed rates ranging from 0.011 m/ka to 0.013 m/ka. These rates are comparable to geochemically derived rates in previous studies. Standard p-wave seismic reflection data were insufficient for detecting boundaries as the weathering boundaries are gradational and do not produce reflections. Shear-wave models also showed internal velocity variations that may be caused by weathering heterogeneity due to textural differences in parental lava flows. Soil chemistry revealed the nature of weathering products as enriched in Al, Fe, Ni, and Cr, and commonly contain alteration minerals such as halloysite, kaolinite, maghemite, and ferrihydrite. Imaging depth limitations were overcome by innovative experiment designs, pushing the boundaries of the current technology. Increasing offsets and combining dispersion curves allowed for a more objective picking of the dispersion curve into the lower frequency domain. Even further improvements were made from a newly developed form of the active/passive technique. These advancements in technology allowed for detailed imaging of the subsurface with greater modeling confidence. This study showed that velocity models derived from MASW are accurately able to describe laterite weathering profiles in terms of depth and variability, expanding the use of the MASW technique beyond its traditional applications and making it a potential tool of interest for many fields of geoscience.

Made available in DSpace on 2017-07-10T17:30:32Z (GMT). No. of bitstreams: 1 ELIZANDRA_BERTUOL.pdf: 4697203 bytes, checksum: 4058cf1fefa0969edd3033b8a4d60c1f (MD5) Previous issue date: 2014-07-21 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The present study examined the stage of weathering of the surface coverage for the geomorphologic surface V, located in Clevelândia (PR) in the field of the Araucária Plateau. To this end, we analyzed the characteristics of the physical and chemical properties of materials in the profile; was determined from the free, total, and the crystalline iron and the total chemical ten (10) major oxides by X-ray fluorescence finally, there is the micro morphology organization of materials. The weathering profile presented more than 710 cm of exposed material, with gradual transition horizons: A (0-20 cm), AB (20-60cm), BA (60-110 cm), Bw1 (110-210 cm), Bw2 (210-350 cm), BC (350-470 cm) and CB (470- 540 cm) and C (540 - 710+ cm). The characterization of physical and chemical attributes of the weathering profile showed native soil cover, with features Oxisols red with acric character. The mineralogical analysis of the material indicated weathering stage characterized by partial hydrolysis environment, the monossialitization type. Associating soil and geochemical characteristics, one realizes that it is weathering profile whose evolutionary process is to ferruginization. The results confirm the hypothesis that the surface V was prepared by the action of etchplanation from the lowering of the substrate by isovolumetric loss generating planing. / O presente trabalho verificou o estágio de intemperismo da cobertura superficial para a superfície geomorfológica V, localizado em Clevelândia (PR), no domínio do Planalto das Araucárias. Para tal, analisou-se as características dos atributos físicos e químicos dos materiais no perfil; determinou-se o ferro livre, total e amorfo e a química total dos dez (10) principais óxidos por fluorescência de raios-X e, por fim, verificou-se a organização micromorfológica dos materiais. O perfil de intemperismo apresentou mais de 710 cm de material exposto, com transição gradual de horizontes: A (0 20 cm), AB (20- 60 cm), BA (60 110 cm), Bw1 (110 - 210 cm), Bw2 (210 350 cm), BC (350 470 cm), CB (470- 540 cm) e C (540 710+ cm). A caracterização dos atributos físicos e químicos do perfil de intemperismo mostrou cobertura pedológica autóctone, com características de Latossolo Vermelho Distroférrico com caráter ácrico. A análise mineralógica dos materiais indica estágio de intemperismo avançado, caracterizado pelo ambiente de hidrólise parcial, do tipo monossialitização. Associando caraterísticas pedológicas e geoquímicas, percebe-se que se trata de perfil de intemperismo cujo processo evolutivo é o de ferruginização. Os resultados confirmam a hipótese de que a superfície V foi elaborada pela ação da etchplanação, a partir do rebaixamento do substrato por perda isovolumétrica gerando o aplainamento.

Made available in DSpace on 2017-05-12T14:42:06Z (GMT). No. of bitstreams: 1 ELIZANDRA_BERTUOL.pdf: 4697203 bytes, checksum: 4058cf1fefa0969edd3033b8a4d60c1f (MD5) Previous issue date: 2014-07-21 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The present study examined the stage of weathering of the surface coverage for the geomorphologic surface V, located in Clevelândia (PR) in the field of the Araucária Plateau. To this end, we analyzed the characteristics of the physical and chemical properties of materials in the profile; was determined from the free, total, and the crystalline iron and the total chemical ten (10) major oxides by X-ray fluorescence finally, there is the micro morphology organization of materials. The weathering profile presented more than 710 cm of exposed material, with gradual transition horizons: A (0-20 cm), AB (20-60cm), BA (60-110 cm), Bw1 (110-210 cm), Bw2 (210-350 cm), BC (350-470 cm) and CB (470- 540 cm) and C (540 - 710+ cm). The characterization of physical and chemical attributes of the weathering profile showed native soil cover, with features Oxisols red with acric character. The mineralogical analysis of the material indicated weathering stage characterized by partial hydrolysis environment, the monossialitization type. Associating soil and geochemical characteristics, one realizes that it is weathering profile whose evolutionary process is to ferruginization. The results confirm the hypothesis that the surface V was prepared by the action of etchplanation from the lowering of the substrate by isovolumetric loss generating planing. / O presente trabalho verificou o estágio de intemperismo da cobertura superficial para a superfície geomorfológica V, localizado em Clevelândia (PR), no domínio do Planalto das Araucárias. Para tal, analisou-se as características dos atributos físicos e químicos dos materiais no perfil; determinou-se o ferro livre, total e amorfo e a química total dos dez (10) principais óxidos por fluorescência de raios-X e, por fim, verificou-se a organização micromorfológica dos materiais. O perfil de intemperismo apresentou mais de 710 cm de material exposto, com transição gradual de horizontes: A (0 20 cm), AB (20- 60 cm), BA (60 110 cm), Bw1 (110 - 210 cm), Bw2 (210 350 cm), BC (350 470 cm), CB (470- 540 cm) e C (540 710+ cm). A caracterização dos atributos físicos e químicos do perfil de intemperismo mostrou cobertura pedológica autóctone, com características de Latossolo Vermelho Distroférrico com caráter ácrico. A análise mineralógica dos materiais indica estágio de intemperismo avançado, caracterizado pelo ambiente de hidrólise parcial, do tipo monossialitização. Associando caraterísticas pedológicas e geoquímicas, percebe-se que se trata de perfil de intemperismo cujo processo evolutivo é o de ferruginização. Os resultados confirmam a hipótese de que a superfície V foi elaborada pela ação da etchplanação, a partir do rebaixamento do substrato por perda isovolumétrica gerando o aplainamento.

Dans la région de Dimbokro-Bongouanou (Centre Est de la Côte d'Ivoire), l'alimentation en eau des populations se fait essentiellement au moyen de puits et forages. Ceux-ci ont été implantés dans les aquifères du socle au cours des différentes campagnes d'hydraulique villageoise mises en place dans ce secteur. L'analyse du taux de réussite et de la productivité de ces forages montre que leur implantation n'a pas toujours été optimale. Afin d'optimiser l'implantation de nouveaux forages, il semble donc nécessaire et primordial de caractériser l'hydrodynamique du socle fracturé. A cette fin, la présente étude procède d'abord à une caractérisation géologique puis hydrogéologique de la région de Dimbokro-Bongouanou. Ensuite, sont élaborés des modèles conceptuels géologiques et hydrogéologiques, qui décrivent la structure de l'aquifère et précisent les propriétés hydrodynamiques de ses différentes couches composites. Ces modèles géologiques et hydrogéologiques permettent de simuler numériquement l'écoulement régional. La caractérisation géologique de la région de Dimbokro-Bongouanou est basée sur une description des différentes formations géologiques de la région ; des hypothèses sur leur mise en place et les cycles d'érosion et d'altération qu'elles ont subis ; et une cartographie des discontinuités régionales par photo-interprétation d'image Radar rehaussée par la technique de filtrages adaptatifs. Les discontinuités identifiées sur l'image rehaussée sont validées à partir d'informations géologiques (données de fracturation mesurées à l'affleurement et données de fracturation relevées sur carte géologique).La caractérisation hydrogéologique de la région de Dimbokro-Bongouanou est basée sur la description des aquifères de la région et l'identification du rôle des discontinuités régionales dans les écoulements souterrains. La technique proposée à cet effet consiste à analyser les corrélations entre le débit des forages et leur distance au linéament le plus proche.Il est ainsi constaté que le débit des forages est inversement proportionnel à la distance à la discontinuité la plus proche. En d'autres termes, plus le forage est proche d'une discontinuité régionale, plus son débit est important. L'interprétation des lithologs, des données géologiques à l'affleurement et des données de résistivités électriques permet de proposer un modèle conceptuel géologique représentatif du profil d'altération type pour chaque domaine géologique de la région. En particulier, le modèle proposé décrit la structuration verticale du profil d'altération pour les trois principales formations géologiques de la région: les granites, les métasédiments et les métavolcanites. La caractérisation de la structure de l'aquifère permet ensuite de proposer un modèle conceptuel hydrogéologique pour chacun des profils d'altération basé sur l'analyse statistique des arrivées d'eau et de l'interprétation des données d'essais par pompage de différents forages. Cela permet d'identifier pour chaque formation les profondeurs de fréquence, de densité et de débit des arrivées d'eau ainsi que les couches du profil associées aux zones de conductivité et de productivité (débit spécifique) élevées.L'ensemble de ces informations géologiques et hydrogéologiques permet de proposer une modélisation conceptuelle de l'hydrosystème étudié (une partie du Bassin du NZI,environ 6300km2) ainsi qu'une modélisation numériques de l'écoulement, celle-ci servant de base à une réflexion sur la pertinence de l'information disponible et d'une modélisation discrète dans ce type d'environnement au vu des objectifs affichés (modèle de gestion et d'aide à la décision pour l'implantation de nouveaux forages). / The hydraulic characterization of fractured basement in Dimbokro-Bongouanou region, Côte d'Ivoire, is an essential step to achieve an optimization of new well locations, in terms of success rates and productivity.To this end, this study first proposes conceptual models of weathering profile for the three main geological formations of the region: granites, metasediments and metavolcanic rocks. Based on in-situ observations, interpretations of lithology and cycles of erosion and alteration, the typical weathering profiles are proposed for each type geological. These are formed from top to bottom of layers alloterite, isalterite, fissured and fractured fresh basement. The fissured layer shows the maximum density of fractures in the metavolcanic rocks and métasédiments, while the fractured fresh basement concentrates the highest density of fractures in granites. Moreover, interpretation of data from pumping tests conducted in various hydraulic programs indicate that the productivity of wells is not proportional to the depth due to variation, at region scale of the thickness of the fissured layer and fractured fresh basement which totalize the maximum of water arrivals. The spatial variation of hydraulic conductivity and productivity (specific rate) is influenced by the thickness of the fissured layer, alloterite layer of the weathering profile and topography. The regional fractures of the fractured fresh basement are also areas of high productivity, as evidenced by the negative correlation between rate of productive wells and distance to these fractures. A methodology of regional fractures mapping from the use of a Radar image and hydrogeological data is suggested.All of these geological and hydrogeological informations are finally integrated into a flow model and the simulated groundwater levels are compared with measured piezometric. It thus appears that the values of hydraulic conductivities deduced from pumping tests are 103 times lower than those that reproduce the regional flow. In addition, a dual approach (equivalent continuum for alterite layer and fissured layer vs. discrete fracture of the base) confirms the role of accidents in the regional flows.

Exotic pine plantations are a major landuse within the coastal lowlands of southeast Queensland, extending from close to the shoreline to the hinterland ranges. These plantations are within a sub-tropical climatic zone, and in most years, the summers are appreciably wetter than the winters. This terrain, in general, has been highly weathered and the soils are poor in nutrients. Environmental factors such as the climate, topography and weathering profile (including soil) are found to be important controls on vadose zone hydrology, which, in turn, has a great impact on tree growth and consequently on the design of management practices. This research project takes a holistic approach to investigate the influence of these environmental factors at different scales, and is designed to fulfil the following objectives: (1) To build a spatial model of forest productivity for the entire Tuan Toolara State Forest (TTSF), southeast Queensland, by analysing the spatial patterns of many environmental variables that may have controls on soil water distribution. (2) To determine how some of these environmental factors are responsible for the development of water-logging and soil salinisation by examining in detail an area of low site index that is severely affected by these two processes. (3) To develop a model to assess the risks of water-logging spatially and temporally. A multiple regression model was constructed to predict the forest productivity (measured by the value of site index, the average dominant tree height at 25 years of age). The independent variables were derived from a digital elevation model (elevation, slope, curvature, hillshade, flow accumulation and distance to streams), γ-ray spectrometry (potassium, thorium and uranium), and interpolated rainfall. The model explained up to 60% of the variance in the site indices and produced predictive maps of site index for two species: P. elliottii Engelm. and Queensland hybrid, a P. elliottii × P. caribaea Morelet hybrid. The model also identified the lowest site index area at the northern Tuan State Forest (NTSF), likely due to a greater risk of water-logging and salinisation. The NTSF area is of low relief and, therefore, the focus has been on the vertical controls of deep weathering profile. The methodology included setting up a network of groundwater bores screened at different depths within the weathering profile, characterising the profile (mineralogy, EC, and pH) and the groundwaters within it (water levels, physico-chemical parameters, major and minor ions). It is found that water-logging is caused by perched groundwater formed on top of the ferricrete or mottled saprolite after prolonged rainfall. Localised salinisation is related to the discharge of brackish groundwater occurring within the mottled saprolite. The deep aquifer within the coarse saprolite is fresh and not responsible for salinisation, a situation that differs from many other settings in Australia. The ability of using the Soil and Water Assessment Tool (SWAT) computer model to simulate soil water balance and to assess the risks of water-logging was tested in a selected catchment in the TTSF. The model successfully simulated stream flow at 2 weirs for a period of 6 years; the achieved R2 were 0.752 and 0.858, respectively. Long-term simulation for a 30-year period showed that there are pronounced seasonal patterns in rainfall and evapotranspiration as well as in soil water. For mature plantation with slopes of 3-15%, the mean annual duration of water-logging ranged from 161 days in the humus podzols, to 110 days in the gleyed podzolic, and to 90 days in the yellow podzolics. The outcomes of this research suggest that forest management can be strongly supported by understanding the impacts of these environmental factors (e.g. climate, topography and weathering profile) on vadose zone hydrological processes; the selection of optimum approach will depend on the research objective or purpose. The models and analytical tools that were developed or tested here have the potential to be successfully applied elsewhere if the input data are available.

[pt] Embora uma vasta área do Brasil esteja localizada em regiões que a formação de basalto se faz presente, são raros os estudos em perfis contendo solo e / ou rochas de caráter básico objetivando correlacionar características químicas e mineralógicas com características geotécnicas. A área do presente estudo localiza-se em um corte em solo na Ferrovia Norte-Sul, no Município de Arguianópolis-TO, em que durante sua execução ocorreram diversos escorregamentos. O maciço de solo do corte em questão é composto em sua maior parte por solos provenientes de alteração de basalto. O presente estudo foi realizado em duas etapas. A primeira refere-se à visita ao local do corte, onde foram realizadas coletas de amostras de solo de caráter indeformado e deformado, com as respectivas descrições morfológicas dos mesmos. A segunda refere-se aos trabalhos desenvolvidos nos laboratórios de Geotecnia e Meio Ambiente do DEC da PUC-Rio, EMBRAPA SOLOS e Departamento de Geologia do Instituto de Geociências da UFRJ, abrangendo ensaios de caracterização; ensaios mineralógicos; análises químicas; obtenção das curvas características solo-água; ensaios de erodibilidade; ensaios especiais para a determinação de parâmetros de resistência e de compressibilidade. A partir dos resultados obtidos, espera-se que os mesmos proporcionem uma contribuição para o melhor entendimento de perfis intempéricos em rochas de caráter básico. / [en] In spite of the fact that basalt formations are found in several regions in Brazil, it is difficult to find investigations on the subject relating chemical and mineralogical characteristics with geotechnical ones. The site of the present study comprises a soil slope on the North-South Railroad, at Arguianópolis, Tocantins State. Several landslides occurred during the construction of the railway. The soil mass is mostly composed by soils resulting from basalt alterations. The present study was developed in two stages. The first stage comprised a visit to the site, when a morphologic description of profiles was made and undisturbed and remoulded soil samples were extracted. The second stage refers to works developed at the Geotechnical and Environmental Laboratory of PUC-Rio, at EMBRAPA Soils and at the Geology Department of the Institute of Geosciences of the UFRJ. Such works comprised soil characterization tests; mineralogical tests; chemical analyses; definition of soil-moisture characteristic curves; erodobility tests and special tests to determine strength and compressibility parameters. The results obtained provide a contribution to a better understanding of weathering profiles in rocks of basic character.