Instituto Geologico Do Estado Of Sao Paulo

São Paulo, Brazil

Instituto Geologico Do Estado Of Sao Paulo

São Paulo, Brazil
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Riccomini C.,University of Sao Paulo | Crosta A.P.,University of Campinas | Prado R.L.,University of Sao Paulo | Ledru M.-P.,Montpellier University | And 3 more authors.
Meteoritics and Planetary Science | Year: 2011

The near-circular Colônia structure, located in the southern suburbs of the mega-city of São Paulo, Brazil, has attracted the attention of geoscientists for several decades due to its anomalous character and the complete absence of any plausible endogenous geologic explanation for its formation. Origin by impact cratering has been suggested repeatedly since the 1960s, but no direct evidence for this has been presented to date. New seismic data have been recently acquired at Colônia, providing new insights into the characteristics and possible layering of infill of the structure, as well as into the depth to the underlying basement. We review the current knowledge about the Colônia structure, present the new seismic data, and discuss the existing-as yet still indirect-evidence for a possible origin by an impact. The new data suggest the existence of a sedimentary fill of approximately 275m thickness and also the presence of two intermediate zones between sediment and basement: an upper zone that is approximately 65m thick and can be interpreted as a possible crater-fill breccia, whereas the other zone possibly represents fractured/brecciated basement, with a thickness of approximately 50m. Although this depth to basement seems to be inconsistent with the expected geometry of a simple, bowl-shape impact structure of such diameter, there are a number of still unconstrained parameters that could explain this, such as projectile nature, size and velocity, impact angle, and particularly the current erosion depth. © The Meteoritical Society, 2011.

Prado R.L.,University of Sao Paulo | Barbosa E.E.M.,University of Sao Paulo | Mendes R.M.,Instituto Geologico Do Estado Of Sao Paulo | Marinho F.A.M.,University of Sao Paulo | de Oliveira O.M.,Federal University of Santa Catarina
Revista Brasileira de Geofisica | Year: 2011

This paper presents results of a study conducted on laboratory and field in order to analyze the parameter amplitude of electromagnetic wave in qualitative assessment of soil moisture contents. We obtained empirical correlations between instantaneous amplitude of the wave, recorded by GPR - Ground Penetrating Radar, and the values of volumetric sediment moisture contents, obtained by TDR - Time Domain Reflectometer, in laboratory experiment as well as in soil samples in a field experiment. Results showed that there is a strong correlation between environmental moisture contents and instantaneous amplitude parameter of electromagnetic wave. In controlled laboratory conditions, this correlation showed a strong coefficient of determination. However, in the field experiment, the coefficient was only 0.64 due to the small amount of data used. This method is easy to implement through a processing flowchart of rapid execution, and can be used in addition to the velocity attribute usually employed in these correlations. © 2011 Sociedade Brasileira de Geofísica.

Bergue C.T.,University of the Rio dos Sinos Valley | Kotov A.A.,University of Sao Paulo | Maranhao M.S.A.S.,Instituto Geologico Do Estado Of Sao Paulo
Journal of Natural History | Year: 2015

Ephippia of Cladocera (Crustacea: Branchiopoda) are found in the Oligocene deposits of Tremembé Formation (Taubaté Basin, Southeast Brazil). Thirty specimens from a short stratigraphic interval of a 115-m section of a core drilled in Taubaté city, São Paulo state, have been studied. Based on the morphology, we assumed that they might belong to two diferent species of Daphnia (Ctenodaphnia) which lived either in the Tremembé palaeolake or in some surrounding temporary waters. Our find represents the oldest record of fossil ephippia in South America and the second record of Daphnia (Ctenodaphnia) in the former Gondwana. A tentative palaeolimnological interpretation is proposed based on the ephippia occurrences, allied to ostracod and lithological data. © 2015 Taylor & Francis.

Barbosa E.E.M.,University of Sao Paulo | Prado R.L.,University of Sao Paulo | Sobreira M.C.A.,University of Sao Paulo | Samoes R.D.,University of Sao Paulo | Souza C.R.G.,Instituto Geologico Do Estado Of Sao Paulo
Revista Brasileira de Geofisica | Year: 2012

This paper presents results of seismic data from shallow seismic reflection onshore acquisition in the coastal plain of Bertioga (São Paulo State, Brazil) in order to support studies of its geological-geomorphological evolution. By using data from a CMP survey, we sought to analyze and interpret the record of three distinct events: reflected waves, refracted waves and surface waves. From the data processing, three sections were generated: stacked section of the reflected waves, tomographic section from the inversion of travel times of refracted P waves, and S-wave velocity section obtained from the inversion of dispersion curves of surface waves. The integration provided a detailed geological section with information about important contacts of quaternary units, surface of the basement rock and a geological structure that suggests a quaternary reactivation of an inferred fault. © 2012 Sociedade Brasileira de Geofísica.

Lima Junior S.B.,Federal University of Ceará | Prado R.L.,University of Sao Paulo | Mendes R.M.,Instituto Geologico Do Estado Of Sao Paulo
Revista Brasileira de Geofisica | Year: 2012

This paper presents results from the MASW method (multichannel analysis of surface waves) in a hill side area of unsaturated soils in the Ubatuba City, Brazil, a site where numerous mass movements have occurred. It discusses the influence of some acquisition parameters, such as, the natural frequency of geophones and minimum and maximum offsets in dispersion image results and does a comparative analysis of the results obtained in repeated tests carried out in the same place, under the same conditions, during the dry and rainy seasons. The comparative analysis for the inversion results in different periods showed that the values of S-wave velocity during the dry season were higher than those for the rainy season; these variations were attributed to the higher cohesion of the soil structure in the dry season. The final 1D velocity profile model with depth was consistent with the results of other geophysical and geotechnical investigations made. Although additional in situ and laboratory geotechnical tests, are necessary (to obtain soil parameters such as hydraulic conductivity, moisture content, soil suction, for example), for a complete characterization of the geotechnical properties of the investigated soil, the result shows that it is possible to use empirical correlations between the Vs profile, from the MASW method, and soil stiffness parameters in order to monitor areas susceptible to landslide. © 2012 Sociedade Brasileira de Geofísica.

Barbosa E.E.M.,University of Sao Paulo | Prado R.L.,University of Sao Paulo | Mendes R.M.,Instituto Geologico Do Estado Of Sao Paulo | Marinho F.A.M.,University of Sao Paulo
Revista Brasileira de Geofisica | Year: 2010

This paper makes an analysis of the quantitative correspondence between the GPR-TDR and GPR-gravimetric measurements of moisture content. The data were obtained from laboratory and field experiments. In the laboratory test, the vadose zone was simulated by injecting and draining water in a sand tank. The experiment was conducted with 1 GHz antennas. The in situ test was carried out on unsaturated residual soils, in an area susceptible to landslide, with 200 MHz antennas. To measure soil water content with GPR, we used the velocity of ground wave, refracted and reflected waves. The GPR response was sensitive to changes in subsurface moisture in both experiments and showed good correspondence with TDR (RMS error of 0.007 m3m-3) and gravimetric (RMS error of 0.039 m3m-3) measurements. © 2010 Sociedade Brasileira de Geofísica.

PubMed | University of the Rio dos Sinos Valley and Instituto Geologico Do Estado Of Sao Paulo
Type: Journal Article | Journal: Anais da Academia Brasileira de Ciencias | Year: 2015

Non-marine Oligocene ostracods from Trememb Formation (Taubat Basin, Southeast Brazil) are studied for the first time. The study reveals rich assemblages which are probably composed of many new taxa, two of which are described here. The sixteen ostracod species registered are classified in the generaCypretta Vvra, Strandesia Stuhlmann,Potamocypris Brady, Heterocypris Claus,Eucypris Vvra, Herpetocypris Brady and Norman, Cytheridella Daday and LimnocythereBrady. Two new species of the latter are herein proposed: L. mandubi sp. nov. and L. katu sp. nov. The succession of ostracod assemblages along the studied core changes conspicuously in composition, abundance and preservation, and are characterized by the following associations: Herpetocypris-Cytheridella (lower), Limnocythere-Cypretta (middle) andPotamocypris-Heterocypris (upper). It is assumed that these associations represent different ecological phases of the paleolake Taubat which is in accordance to previous stratigraphic and paleontological studies in the basin. The results from this pioneering taxonomic and paleoecological study on ostracods from Trememb Formation reinforce the potential of these fossils for paleolimnological researches in Brazilian Cenozoic deposits.

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