SELF-INDENTATION OF A HETEROGENEOUS CONTINENTAL LITHOSPHERE

The Neoproterozoic Ribeira-Aracuai belt stretches along the southeaste rn edge of the Sao Francisco craton of southeastern Brazil and extends south of the cratonic domain for > 1000 km. The termination of the cr aton is spatially correlated with a significant modification of the de formation pattern in the belt: (1) the structural trend bends from due north to northeast, (2) the dominant tectonic flow shifts from orogen -transverse to orogen-normal, and (3) the metamorphic conditions of de formation decrease southwestward from high to medium grade. Finite-ele ment modeling suggests that the presence of a craton within a continen t favors strain localization, initiation of continental-scale shear zo nes, and differential vertical deformations. The southward termination of the Sao Francisco craton may have triggered the development of the complex deformation pattern that characterizes the Ribeira-Aracuai be lt.