CHAMP satellite and terrestrial magnetic data help define the tectonic model for South America and resolve the lingering problem of the pre-break-up fit of the South Atlantic Ocean

Abstract

In July 2000, a new potential fields satellite was launched and is currently measuring the earth's gravity and magnetic fields (the latter down to 0.1 nT). The satellite, called CHAMP (CHAllenging Mini-satellite Payload), will be providing high accuracy crustal magnetic field data of the earth for wavelengths of about 300–3000 km until about 2005. Previous magnetic satellites have been reviewed by Ravat and Purucker ( TLE , 1999) who found that an excellent comparison could be made between the long wavelength component of the DNAG magnetic field (>500 km) covering North America and the Magsat satellite field. Magsat was limited to a six-month operating period due to its low orbital altitudes (between 352 and 578 km) before burning up in the atmosphere in June 1980. Its large variation in orbital altitude was one factor that made generation of the crustal field component difficult. The CHAMP crustal field, on the other hand, is derived from solar night data, for which the magnitude and complexity of the transient variation corrections are significantly reduced—making for a more stable crustal field solution with significantly greater resolution. As we will show in this article, resolution of the satellite magnetic field over the Atlantic Ocean is sufficient to map subtle coherent features (<1 nT in amplitude) which are interpreted as bulk changes in the remanence of the oceanic crust associated with the linear magnetic reversals pattern of the geomagnetic field during and since the Mesozoic period. Such resolving power of these N-S striking anomalies, which subparallel the orbital tracks, provides confidence that the larger magnetic variations imaged over the continents are being reliably mapped and can aid identification of geologic provinces of interest in petroleum and mineral exploration. Comparisons of the satellite and terrestrial aeromagnetic data over Brazil show that the Trans Brazilian Lineament, a major continental …