Paulo César Soares

Quaternary of the Pantanal, west-central Brazil

Abstract The Pantanal is a tectonic depression located at the left margin of the Upper Paraguay River. The Paraguay is the trunk river of an alluvial depositional tract composed by several large marginal alluvial fans, the Taquari fan being the largest one. The present landscape is a complex tropical wetland characterized by month-long floods every year, with geomorphic features derived from the present conditions and others inherited from successive Pleistocene and Holocene climates. Some areas containing ponds are landscape relicts generated by eolian deflation during the Last Glacial Maximum. Many ponds, closed depressions isolated from the superficial waters by vegetated crescent ridges of fine sands, were interpreted as salt pans bordered by lunette sand dunes. Initiation of the modern wetland has occurred during the Pleistocene/Holocene transition, with the change to a more humid climate and the individualization of lacustrine systems. Active tectonics has been playing an important role in the development of the Pantanal landscape. Nowadays, the Paraguay River meanders in a large flood plain with extensive swamp surfaces, being structurally constrained by faults in the west border of the basin. Sedimentation within the Pantanal wetland is also affected by tectonic activity, especially along faults associated with the Transbrasiliano Lineament.

Mechanical properties of kaolinite ‘macro-crystals’

The mechanical properties of a rare sample of kaolinite macroscopic crystals were evaluated using instrumented indentation. The crystals were also characterized by X-ray diffraction, scanning electron microscopy, atomic force microscopy and Fourier transform infrared spectroscopy before and after heat treatment at 1100°C. The results are explained in terms of the fracture process occurring in the layered structure of kaolinite, and of the effect of roughness on the hardness and elastic modulus. Data analysis using One-way ANOVA (p < 0.05) showed that the values of hardness and elastic modulus obtained are statistically homogeneous. Before heat treatment, the sample was composed essentially of kaolinite, with hardness of 42 MPa and elastic modulus equal to 1.3 GPa. After calcination at 1100°C, the sample keeps its layered habit and consists of amorphous metakaolinite. The hardness increases to 360 MPa and the elastic modulus increases to 6.9 GPa.

A record of Permian subaqueous vent activity in southeastern Brazil

The remarkable occurrence of more than 4,500 conical siliceous mounds in an area of less than 1.5 square kilometres has been reported in the Paraná basin, near Anhembi, São Paulo, in southeastern Brazil. These structures, which are up to two metres high, are thought to have been formed at the margin of a very shallow, broad but waning internal sea, and it was originally suggested that they are stromatolites. Yet their restricted occurrence, unusual abundance and nearly pure siliceous composition have never been satisfactorily explained by this hypothesis. Here we report field and laboratory observations on their shape, construction, composition and mineralogy. On the basis of our data we suggest that the conical mounds are the result of subaqueous Late Permian vent activity in southwestern Gondwana. The present siliceous cone field differs considerably from other Palaeozoic siliceous hot spring deposits, such as those at Rhynie, Scotland, and the Drummond basin, Australia, and therefore represents an unusual occurrence of vent activity.

Heterogeneidades hidroestratigráficas no Sistema Aqüífero Guarani

The main regional aquifer of South America is the Guarani Aquifer System (SAG), it is made up mainly of the psamitic Piramboia and Botucatu formations (Brazil), Misiones (Paraguay and Argentina) and Taquarembo (Uruguay), with a maximum thickness of 600m. The aquifer system lies unconformable over different Paleozoic formations and is covered by extensive basaltic flows of Early Cretaceous age. The aquifer is not a homogeneous blanket sandstone, but composed of facies association whose geometry and architectural elements allow to subdivide it in flows units. These units have different hydraulic conductivity and as consequence different hydrodynamic and hydrochemical behavior. Stratigraphic analysis using field and well data allows to construct a model of depositional systems and reservoirs properties distribution. The aquifer is divided in tree main flow unities: dune (DU), interdune (ID) and channel (CH); and secondary, two others: crevasse (CR), and lacustrine and flood plain (FF). Each one has facies characteristics, and the grain distribution allow inferring the effective porosity and permeability. Botucatu DU presents average hydraulic conductivity one order o magnitude grater than Piramboia interdune, meaning ten times the potential of water flow velocity. The humid interdune blanket sands bellow Botucatu and interbeded in the Piramboia dunes may be considered a strong aquitard. The space distributions of the unities have a direct effect in quality and flow of water inside the regional aquifer. The data and results lead to the recognition of five main regional stratigraphic domains around the Parana basin

Bayesian and multivariate methods applied to favorability quantification in recôncavo Basin and Ribeira Belt, Brazil

A methology to define favorable areas in petroleum and mineral exploration is applied, which consists in weighting the exploratory variables, in order to characterize their importance as exploration guides. The exploration data are spatially integrated in the selected area to establish the association between variables and deposits, and the relationships among distribution, topology, and indicator pattern of all variables. Two methods of statistical analysis were compared. The first one is the Weights of Evidence Modeling, a conditional probability approach (Agterberg, 1989a), and the second one is the Principal Components Analysis (Pan, 1993). In the conditional method, the favorability estimation is based on the probability of deposit and variable joint occurrence, with the weights being defined as natural logarithms of likelihood ratios. In the multivariate analysis, the cells which contain deposits are selected as control cells and the weights are determined by eigendecomposition, being represented by the coefficients of the eigenvector related to the system’s largest eigenvalue. The two techniques of weighting and complementary procedures were tested on two case studies: 1. Recôncavo Basin, Northeast Brazil (for Petroleum) and 2. Itaiacoca Formation of Ribeira Belt, Southeast Brazil (for Pb-Zn Mississippi Valley Type deposits). The applied methdology proved to be easy to use and of great assistance to predict the favorability in large areas, particularly in the initial phase of exploration programs.

Interpretação qualitativa e semiquantitativa dos dados aeromagnéticos sobre a Zona de Cisalhamento Lancinha, porção meridional do Cinturão Ribeira no estado do Paraná, sul do Brasil

The characterization of shear zones at the southern portion of the Ribeira Belt, PR, BR, as well as its recognition in depth is a major challenge. Despite the lack of subsurface information, the influence of such structures on the installation and evolution of the Parana Basin during the Phanerozoic is widely accepted. Therefore, in this paper, are applied methods of anomaly enhancement (qualitative analysis) and estimative of the sources depth (semiquantitative analysis), on the aeromagnetic coverage of the Lancinha Shear Zone area (LSZ) in the Parana state, in order to verify its spatial arrangement in subsurface. The processing resulted in the interpretation of magnetic-structural framework of the study area, which was validated by the depth estimative of the magnetic sources (Euler solutions). The results indicated the extension of the Lancinha, Morro Agudo and Itapirapua shear zones under the Parana Basin coverage.

Titanium bioactivity surfaces obtained by chemical/electrochemical treatments

There are various surface treatments used to modify titanium surfaces to render it bioactive. In this study commercially pure titanium surfaces (cp Ti), grade 2 were modified by acid etching (AE) and anodic oxidation (OA) in order to evaluate the bioactivity in vitro of these surfaces using the simulated body fluid (SBF). The AE was realized using a mixture of acids and AO using 1 mol.L-1 sulfuric acid. The anodic films were obtained under potentiostatic mode, during 60s using as anode a bar of titanium. All the surfaces that means cp Ti, AE and AO were analyzed concerning to morphology, rugosity, structural changes before in vitro bioactivity tests. It was observed by scanning electron microscopy (SEM) that all surfaces presented different morphologies: those with AE showed a surface with peaks and rounded valleys, with Ra = (564±80) nm, the oxidized surfaces with sulfuric acid showed a morphology with small pores uniformly distributed over the surface and Ra = (177±0,02) nm. X-rays diffraction results showed the presence of titanium hydride on the samples with AE and the anatase and rutile phases on the anodic films after heat treatment at 600°C/1h. Bioactivity tests in vitro using SBF at 37°C showed that small aggregates containing Ca and P were observed on surfaces with AE after 30 days soaked in SBF and the surfaces oxidized were fully coated with an apatite layer, identified by SEM.

Contradições na pesquisa e pós-graduação no Brasil

Scientific progress in Brazil has been subjected to a process of search and evaluation set by international targets and has achieved outstanding results. However, the same is not true for technological development or for school education. With notable exceptions, scientific progress has not translated into competence gains and improvements in the quality of life. The results achieved in science and technology and in the education of researchers are examined here to evaluate the hypothesis that severe contradictions exist between the education of researchers and scientific and technological results, which are in contrast with the needs of a society that strives to achieve tolerable standards, comparable to those of other nations. The discussion points to a strong trend to academicism, both in education and in research, that seeks to repeat results achieved by already developed societies. As a conclusion, greater effort from the scientific community is necessary in the new organizational environment to attain more effective and pragmatic results in research and in the development of researchers and teachers, as a means of making the society the largest beneficiary of knowledge.