Conventional shipborne gravity data were integrated with gravity data derived from satellite altimetry over a region in the South Atlantic Ocean situated between 65/25ºW and 25/40ºS. This region includes physiographic and tectonic features such as part of the São Paulo Plateau, the Rio Grande Rise, the Pelotas Basin and the Rio Grande Fan. Least squares collocation was used in order to obtain free-air anomaly and geoid height models, with nominal resolution of 10'. Shipborne gravity data was mostly obtained from GEODAS data bank updated until 1995 and the satellite derived gravity data were measured during one year of GEOSAT/Exact Repeat Mission. The present free-air anomaly model was compared with two other recent models derived from different satellite altimetry missions. The methodology used in the present study produces noise-free gravity field models for the oceans in contrast with models based solely on satellite altimetry. Apart from this result, the integration of conventional marine gravity data is fundamental on improving the gravity field in regions of water depth shallower than 1,000 m, such as over the continental margins, where satellite data are not reliable. As an example of the potentiality of the obtained free-air and geoid anomalies, a preliminary qualitative analysis of their tectonic significance is presented with emphasis on the dynamical implications on the evolution of the southern segment of the Brazilian continental margin and adjoining oceanic lithosphere.
Marine gravity; South Atlantic; Satellite Altimetry
