INGEIS   05370
INSTITUTO DE GEOCRONOLOGIA Y GEOLOGIA ISOTOPICA
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Magnetotelluric Study in the Guarani Deep Thermal Aquifer System, NE Argentina
Autor/es:
FAVETTO, ALICIA; POMPOSIELLO, MARIA CRISTINA; DAPEÑA, CRISTINA; CURCIO, ANA
Lugar:
Beijing, China
Reunión:
Workshop; 19th IAGA WG 1.2 Workshop on Electromagnetic Induction in the Earth; 2008
Institución organizadora:
Institute of Geology, China Earthquake Administration Geo-Electromagnetic Committee, Chinese Geophysical Soc
Resumen:
The Guaraní Aquifer System (GAS) is one of the most important transboundary groundwater reservoirs covering an area of ca. 1.200.000 km2.
It forms part of the Paraná and Chacoparanense sedimentary basin and it
is shared by Brazil, Paraguay, Uruguay and Argentina. The geological
units related to this system are the Triassic-Jurassic eolian and
fluvial sandstones of the Piramboia and Botucatu Formations, and the
Serra Geral Basalts which present clastic intercalations. This effusive
Cretaceous complex covers the sandstones and provides a
high-confinement degree. The research activities carried out in each
country by scientists coming from different disciplines and
institutions allowed them to define the main characteristics of this
deep thermal aquifer system. The geological, hydrogeological,
hydraulic, hydrochemical and thermal characteristics of the GAS vary
throughout the whole basin and are controlled by variations in the
depositional environment, in the structural evolution and in the
residence time of water within the formations, which generate
heterogeneities and point out the presence of compartments and,
consequently condition the recharge mechanisms, storage, circulation
and water quality. The object of our previous vertical electrical
soundings (VES) was to estimate the geometry of the geological units,
the depth of the top of the crystalline basement and to evaluate the
existence of thermal waters in the southeastern part of the Entre Ríos
province, Argentina. Considering that the main factor determining the
presence of the sediments which contain the GAS, in this area, is the
structural setting which is directly related to the depth of the
crystalline basement top, new MT sites were collected during 2007-2008
along an N-S profile. Geoelectrical models coming from this profile and
also from a previous deployment along an E-W profile allowed us to find
the depth of the sediments - crystalline basement interface. Although,
at the western part of Entre Ríos province, the depth of the
crystalline basement obtained from the E-W MT model is around 4000 m
and it should be difficult determined the prolongation of the Serra
Geral Basalts because of fractures and clastic intercalations with high
conductivity due to the presence of very saline waters. The results
have been correlated with the existing thermal wells and significant
variation in the basement depth is shown.