Modelo gravimétrico-magnético do Gráben de Paranaguá-PR, Brasil

Abstract

We study the Paranaguá Graben, which is part of the Cenozoic Rift System of southeastern Brazil. Specifically, it is considered a gravimetric-magnetic model of the top of the Precambrian basement under the Cenozoic sediments of the Paraná state coastal plain. We aim to identify the main structures of the Paranaguá Graben. We also evaluate the thickness of the sedimentary section and the Mesozoic basic intrusions in the basement. We use a regional geophysical survey that extends for more than 55 km of gravimetric profiles with 500mof spacing between the stations and about 45 km of magnetic profiles with spacing of 25 m. The geophysical profiles were located between Paranaguá Bay and the Saí-guaçú river outlet, both in the context of the central region of the Ponta Grossa Arch (PGA). Data were collected along NE-SW acquisition lines, perpendicularly to the principal trend of the PGA. We present a 2-D geologic model using on gravity and magnetic data. We incorporate prior knowledge about the basement depth provided by boreholes. The identification of gravity high was related to a basement uplifting (Canoas structural high). Contiguous gravity lows had been interpreted as structural lows and called Albatroz and Shangri-lá, whose maximum thickness of the sediments is 130 m. The magnetic model allowed to estimate the thicknesses of the basic dykes and to calculate an average crustal extension of 27% related to 45 km of the magnetic profiles. © 2008 Sociedade Brasileira de Geofísica.