separating these basins, and includes much evidence of recurrent or resurgent tectonic movements that have been active until recent times. The morphostructural analysis of this region, combined with the characterization of the Quaternary sedimentary deposits and britfle tectonic structures, nas permitted the recognition of tferee phases of neotectonic movements. The oldest movements were related to a NW-SE compressive stress field, during the Pleistocene, associated with an E-W right-lateral transcurrent binary. The structures related to this phase affected colluvium and stone-line deposits, which are often overthrust by bloeks of basement rocks along faults trending NE to ENE. Probably in the begining of the Holocene the stress regime changed to an E-W (WNW-ESE) extension, responsible for the generation of N-S-trending grabens with syntectonic sedimentary filling. Finally, a new change in the stress field is recorded by conspicuous and widespread families of shear joints, systematically orientated ENE and WNW, that affect colluvium, colhiviunvalluvium and alluvium deposits. The accute bissectrix of the families of joints indicate an E-W direction of compression. The reliability of the neotectonic data presented in this study and the proposed neotectonic model are particularly significant due to important human activities in the region, including such major engineering projects as a radioactive fuel factory, a hydroelectric power station and reservoir as well as a nuclear power plant.
RESUMO Existe grande dificuldade em prever o comportamento hidraúlico dos aqüíferos fraturados devido à grande descontinuidade e heterogeneidade que caracteriza estes meios. Como conseqüência, não existe método amplamente aceito para realizar o seu mapeamento, seja com relação às suas potencialidades como vulnerabilidades. Assim, para atender ao objetivo principal do Mapa de Águas Subterrâneas do Estado de São Paulo, que foi o de cartografar e representar áreas com potencialidades hidrogeológicas distintas dentro de cada aqüífero estudado, foi necessário o desenvolvimento de um método que consistiu na avaliação da variação da capacidade específica de poços selecionados com relação aos seguintes fatores: conjuntos litológicos, espessura de manto inconsolidado, densidade e intersecção de lineamentos e blocos geológicos. Como resultado, foram individualizadas quatro classes de potencial hidrogeológico, sendo que três destas correspondem à subdivisão das rochas pré-cambrianas não carbonáticas, cujas medianas de capacidade específica são 0,04 m³/h/m, 0,08 m³/h/m (os diabásios eocretáceos estão englobados nesta classe) e 0,18 m³/h/m. Na classe mais produtiva foram agrupadas rochas pré-cambrianas carbonáticas e basaltos eocretáceos, com medianas de 0,62 e 1,25 m³/h/m, respectivamente. Os limites entre as regiões de rochas pré-cambrianas que apresentam produção distinta correspondem principalmente a importantes zonas de cisalhamento, que delimitam em parte terrenos com evolução geológica distinta, e secundariamente a descontinuidades francamente rúpteis. Palavras chave: aqüíferos fraturados, Estado de São Paulo, potencialidade de produção, rochas pré-cambrianas, basaltos eocretáceos ABSTRACT As a consequence of the dificulty in predicting the hydraulic behaviour of the fractured aquifers, due to their descontinuity and heterogeneity, there is not, up to this moment, any generally accepted method to map this type of media, in terms of both potenciality and vulnerability. In this way, in order to meet the main goal of the Hydrogeological Map of the State of São Paulo, namely, delimitate areas with different goundwater production potentiality, it was necessary to develop a method which consisted on the evaluation of the specific capacity variation of selected wells with regard to: lithologic groups, thickness of the non-consolidated materials (regolith, soil and sediments), density and intersection of lineaments, and geological blocks. As a result, four classes of hydrogeological potential were characterized, three of them corresponding to the subdivision of the non-carbonatic Precambrian rocks, whose specific capacity medians are 0,04 m³/h/m, 0,08 m³/h/m (the Eocretaceous diabases are encompassed by this class) and 0,18 m³/h/m. The most productive class encompasses carbonatic Precambrian rocks and Eocretaceous basalts, with medians of 0,62 and 1,25 m³/h/m, respectively. The boundaries between regions of pre-cambrian rocks with distinct production capacity correspond mainly to important shear zones, which partialy delimitat...
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