Structural Framework of the Southern Brazilian Shield: The Perspective from Gravity Models

New gravity data in southern Brazil are combined with previous data in Brazil and Uruguay, permitting detailed analysis of the basement structure. The Brasiliano cycle tectonic framework suggested by previous geological studies is generally confirmed. Pre-Brasiliano structure (Transamazonian cycle), however, is an important and hitherto unstated source of lateral density contrast responsible for distinctive gravity discontinuities. Individual blocks with the Rio de La Plata craton are recognised and a new block, the Paso del los Toros Block, is defined.