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Large sheath folds in the basal high-pressure nappes of the Cabo Ortegal complex are described and a kinematic interpretation provided. The principal penetrative and map structures relate to regional D2 deformation, which produced foliations (S2) bearing mineral and stretching lineations (L2) and several types of folds (a-type, sheath-like and ‘folded folds’). The latter structures are subparallel to the trend of the orogen. Their attitude suggests that the units involved shared a common tectonic evolution during progressive ductile deformation of an anisotropic medium. Reconstruction of major geological structures was accomplished through projection of map-scale features onto the ductile flow plane and the plane perpendicular to the ductile flow direction. The structures reconstructed illustrate their development in the deeper structural levels of an orogenic channel subjected to high-pressure metamorphism during the early phases of the Hercynian orogeny in NW Iberia. We argue that orogen-normal tectonic displacements (of up to a few hundreds of kilometers) represent the minor components of the transpression with possibly thousands of kilometers along-strike dextral displacement between the intervening plates (during subduction/collision). 相似文献
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Josué Camargo Mendes 《International Journal of Earth Sciences》1957,45(3):540-547
Summary This article is a brief résumé of the geology of the marine Upper Carboniferous beds (Itaituba series) of the Amazonian basin. The unfolded sediments cover a large area of the basin and are constituted of limestones, shales and sandstones. The macrofauna includes brachiopods, pelecypoda, corals, bryozoa, etc., from which the brachiopods are the better known by the present. The microfauna includes two genera of fusulinids:Millerella andFusulinella.According to the age as given by the fusulinids the sediments are Pennsylvanian (Upper Carboniferous), and not Permian as it has been supposed by some authors. So, the correlation with the Andean (Bolivia and Peru) permian groups is no more valid. Correlation with Tarma Group (Upper Carboniferous from Peru) and with the marine carboniferous of the MaranhÃo-Piauí (Brazil) is possible but not very well established. 相似文献
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Pablo M. Cincotta Juan C. Muzzio Josué A. Núñez 《Celestial Mechanics and Dynamical Astronomy》1991,52(3):263-275
We use the impulse approximation to derive analytical formulae for the escape probability from a simple binary system that interacts with a third body. The binary system is made up of a mass-less body in circular orbit around a massive object, and we assume that the two massive bodies follow a Schuster (or Plummer) distribution. Within the ranges imposed by the impulsive approximation to the parameters of the encounter, we find good agreement between our results and those obtained from numerical experiments. 相似文献
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Luiz Alberto Ribeiro Mendonça Horst Frischkorn Marlúcia Freitas Santiago Josué Mendes Filho 《Environmental Geology》2005,47(8):1045-1053
Measurements of the environmental isotopes carbon-14 and oxygen-18 and of the electrical conductivity in ground water, together with MODFLOW-88 (DOS) simulations of pumping tests, were used to achieve a detailed understanding of the functioning of an aquifer in the area of a well field. The methodology was applied in the sedimentary basin of the Cariri region, in the south of Ceará State in Brazil. Localized hydraulic connections between adjacent aquifer units could be detected, and mixing ratios for the contributions from the units involved were determined. Cone of depression simulations for a three-year drought period revealed well interference and a drastic lowering of the piezometric level, thereby explaining the hydrogeologic changes and transformations in vegetation that were observed in the area of the well field. The combined use of the modeling tools and the geochemical field observations is shown to provide more detailed insight into the conceptual model of the groundwater flow system. 相似文献
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Luiz?Alberto?Ribeiro?Mendon?a Horst?FrischkornEmail author Maria?Marlúcia?Freitas?Santiago Josué?Mendes Filho 《Environmental Geology》2004,46(2):295-302
The Araripe Plateau in northeastern Brazil has an area of about 8,000 km2, confined by 39°05E and 40°55E, and 7°10S and 7°50S. Due to high permeability of soils, a surface drainage system is practically inexistent. Water is stored in excavations with clayey soil, the barreiros. Monthly samples were taken for 18O measurements, from September 1999 to August 2000, from four barreiros, three dug wells and five drilled wells. Results show that (1) groundwaters in the eastern part of the plateau are derived from present-day rainfall (18O–3.2), whereas groundwaters in the western portion are isotopically different (18O–5.0); (2) barreiros are strongly marked seasonally by elevated 18O during the dry period due to elevated evaporation; (3) a dug well at a distance of 30 m from a barreiro exhibits 18O similar to that of the reservoir, indicating a strong interaction between groundwater and surface water; and (4) a tubular well of 242-m depth, located in a fault, exhibits strong seasonal changes in 18O and electrical conductivity, revealing downward leakage between aquifers. 相似文献
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Carlos José Freire Machado Maria Marlúcia Freitas Santiago Luiz Alberto Ribeiro Mendonça Horst Frischkorn Josué Mendes Filho 《Aquatic Geochemistry》2007,13(2):187-196
Flow modeling and hydrogeochemical inversion calculations were performed on the aquifer systems of the Crato-Juazeiro Graben
in the Araripe Sedimentary Basin of the Cariri Valley, Northeast Brazil, in order to assess aquifer interconnections through
an aquitard of the Araripe Plateau. Steady state hydraulic head numeric calculations with the finite difference method used
Modflow software with hydrologically based boundary conditions and a piezometric surface as initial condition. Hydrogeochemical
inversion with PHREEQC was performed for two water samples representing typical initial and final waters along the flow path.
Flow simulation shows that approximately 20% of all recharge water from the superior aquifer system passes through the Santana
aquitard reaching the middle aquifer system. Quantification of mineral dissolution/precipitation processes, ion exchange and
microbiological redox reactions taking place in the aquifer systems also indicates hydraulic interconnection of the superior
and middle aquifer systems through the Santana aquitard. 相似文献
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A B‐Spline Framework for Smooth Derivative Computation in Well Test Analysis Using Diagnostic Plots 下载免费PDF全文
In the oil and gas industry, well test analysis using derivative plots, has been the core technique in examining reservoir and well behavior over the last three decades. Recently, diagnostics plots have gained recognition in the field of hydrogeology; however, this tool is still underused by groundwater professionals. The foremost drawback is that the derivative function must be computed from noisy field measurements, usually based on finite‐difference schemes, which complicates the analysis. We propose a B‐spline framework for smooth derivative computation, referred to as Constrained Quartic B‐Splines with Free Knots. The approach presents the following novelties in relation to methodological precedents: (1) the use of automatic equality derivative constraints, (2) a knot removal strategy and (3) the introduction of a Boolean shape parameter that defines the number of initial knots to choose. These can lead to evaluate both simple (manually recorded drawdown measurements) and complex (transducer measured records) datasets. Furthermore, we propose an additional shape preserving smoothing preprocess procedure, as a simple, fast and robust method to deal with extremely noisy signals. Our framework was tested in four pumping tests by comparing the spline derivative with regards to the Bourdet algorithm, and we found that the latter is rather noisy (even for large differentiation intervals) and the second derivative response is basically unreadable. In contrast, the spline first and second derivative led to smoother responses, which are more suitable for interpretation. We concluded that the proposed framework is a welcome contribution to evaluate reliable aquifer tests using derivative‐diagnostic plots. 相似文献
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