2014-08-222014-08-221984-09-21GONZÁLEZ CARRASQUILLA, Antonio Abel. Estudo geofísico regional sobre águas subterrâneas na Ilha do Marajó - Pará - Brasil. 1984. 142 f. Dissertação (Mestrado) - Universidade Federal do Pará, Centro de Geociências, Belém, 1984. Curso de Pós-Graduação em Ciências Geofísicas e Geológicas.https://repositorio.ufpa.br/handle/2011/5494IDESP and NCGG have conducted field work on the East half of the Marajó Island performins over 800 VES (Vertical Electrical Sounding), in the last ten years. The work was done for hidrogeological purposes. A large number of these VES, however, were not adequately interpreted at the time due to lack of application of good quantitative techniques. We have then reinterpreted all the date using recently developed interpretation techniques with the following goals: to present the regional distribution of the main aquifers in the area; to group the VES in characteristics families; to test the goodness of the interpretation; and to propose bidimensional modelling as an alternative technique for interpretation of some of the VES performed in specific locations in the area. Initially, we did interpretation on assumption of a stratified earth and could identify three types of aquifers: 1. The first, named "deep aquifer", is located at depths deeper than 50m and can be found all over the prospected area. It seems to be associated to the upper layers of the Marajo Formation or it could be related to the highly resistive material of the deep layers of Pará Group. 2. The second, named "shallow aquifer", occur in the Southern and Southeastern portions of the area at depths between 10 and 50m. It is associated to the sandy lenses of the Para Group. 3. The least is represented by paleochannels and similar structures. It occurs scattered in a aleatory way in the area, at shallow depths. We have classified the VES after a detailled study in three characteristic families with its respectives types. This study also provided the preparation of maps of location and thickness of the aquifers, and maps of longitudinal conductance and average resistivity. The last ones helped to divided the region of campos of the Marajó Island in three main zones: 1. The first one is highly resistive and located in the Southern and Southeastern portions of the area. It correlates to the outcropping ground of Para Group. 2. The second, highly conductive, is located in the Central and Northern portions of the area, where occur the scattered paleochannels. The ground in this zone presents the lowest topographic values in the area and in general in contains clays and salty water. 3. The third is fairly resistive and it is related to the ground occurring in the neighborhood of the city of Chaves (Northwest of the region of camps), which are similar to that occurring in the Sourthern and Southeastern portions of the area. At last we have tested the interpretation confidence for the horizontally stratified earth conventional model used by applying the inversion technique on one characteristic VES of each family. We found a very high statistical correlation among the model parameters, probably due to the application of a too simple irrealistic geophysical model to the complex real earth of Marajo Island. The results from digital modelling by the finite element method demonstrated the influence of the abrupt lateral variation in resistivity on VES data. The finite element method was also used for modelling a shallow structure similar to a paleochannel. This result suggests that bi-dimensional models can be very helpfull in interpreting resistivity data collected in the region of camps of Marajo.porAcesso AbertoProspecção - Métodos geofísicosÁguas subterrâneasIlha de Marajó - PAPará - EstadoAmazônia brasileiraDissertaçãoCNPQ::CIENCIAS EXATAS E DA TERRA::GEOCIENCIAS::GEOFISICA::GEOFISICA APLICADACNPQ::CIENCIAS EXATAS E DA TERRA::GEOCIENCIAS::GEOFISICA::PROPRIEDADES FISICAS DAS ROCHAS