Luís Alberto Dávila Fernandes¹, Rualdo Menegat²

(1) Federal University of Rio Grande do Sul/CNPq, Porto Alegre - RS, Brazil
(2) Federal University of Rio Grande do Sul

ABSTRACT: A reappraisal of the nature and age of the late-orogenic basins of the Neoproterozoic Dom Feliciano Belt in Southern Brazil

Sequences related to the denudation stages of evolution of the Dom Feliciano Belt (DFB) crop out in the central and western geophysical domains of the DFB in southern Brazil. These rocks are preserved fragments of late-orogenic basins bound by NE-trending faults. These basins of diverse ages and tectonic setting are collectively referred to in the literature as 'Camaquã Basin'. The latter has been classified as a 'retro-arc foreland basin' and correlated with the Nama Group, that is considered as a contemporaneous 'peripheral foreland basin'. Some of these basins have been interpreted as 'back-arc', 'successor', 'foreland', 'piggy-back', 'pull-apart' and strike-slip'. These classifications imply timing and style of deformation typical of a certain tectonic environment and in the case of the late-orogenic basins of southern Brazil, an association with an environment of 'fold-and-thrust belt' is clearly suggested. However, there is no structural or stratigraphic evidence to relate these basins to a collisional process. On the contrary, some of these basins are not only younger than the collisional structures, but also post-date the younger transcurrent deformation. Such diverse interpretations reflects the lack of a model capable of relating each basin to an specific tectonic environment in time and space during the evolution of the DFB. Because of this, the traditional view is based only on lithostratigraphic criteria to correlate sequences of these basins. Our view is that each fragment represents distinct basin controlled by two major tectonic regimes - strike-slip and extension, that followed collision at the end of the Neoproterozoic.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado