Geoelectric structure beneath limestones of the Sao Francisco Basin, Brazil
© The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS); The Seismological Society of Japan; The Volcanological Society of Japan; The Geodetic Society of Japan; The Japanese Society for Planetary Sciences. 1999
Received: 30 November 1998
Accepted: 6 July 1999
Published: 20 June 2014
A reconnaissance MT survey was conducted in the southern portion of the Sao Francisco Sedimentary Basin, Brazil, for mapping the subsurface structure. The objective was to provide a regional model and in helping to select areas to be further surveyed with seismics. The data collected at seven EMAP-style spreads of 500 m, with an average spacing of 30 km. The field procedure allowed for the correction of statics and the production of 7 inverted models, smooth representations of the regional structure as seen below each site. A 2-D forward model tested and refined the regional structure revealed by the inversions and yielded an earth composed of 4 main geologic units. A 100 ohm.m limestone layer on the top of 20 ohm.m shales, followed by a 1000-200 ohm.m structured basement. Crustal resistivities do not change until reaching depths of more than 30 km. The model ends at a conductive half-space of 30 ohm.m. A suture zone between an orogenic belt and the Sao Francisco craton was modeled below the sedimentary section bringing its know limits 60 km to the east.