Basement-cover relationships and deformation in The Northern Paraguai Belt, central Brazil: Implications for the Neoproterozoic-early palaeozoic history of western Gondwana

Abstract

The Northern Paraguai Belt, at the SE border of the Amazonian Craton, central Brazil, has been interpreted as a Brasiliano/Pan-African (ca. 650-600 Ma) belt with a foreland basin, recording collisional polyphase tectonism and greenschist facies metamorphism extending from the late Precambrian to the Cambrian-Ordovician. New structural investigations indicate that the older metasedimentary rocks of the Cuiabá Group represent a Tonian-Cryogenian basement assemblage deformed in two contemporaneous fault-bounded structural sub-domains of wrench- (rake<10°) and contraction- (rake∼30-40°) dominated sinistral transpression, with tectonic vergence towards the SE. The younger late-Cryogenian to early-Cambrian sedimentary rocks lying to the NW of the Cuiabá Group are non-metamorphic and display only pervasive brittle transtension characterized by normal-oblique faults, fractures and forced drag folds with no consistent vergence pattern. Our analyses suggest that an unconformity separates the metasedimentary Cuiabá Group basement of the Northern Paraguai Belt from the unmetamorphosed sedimentary cover. It is proposed that the latter units were deposited during a post-glacial marine transgression (after ca. 635 Ma) in a post-collisional basin. The Paraguai Belt basement and its post-collisional sedimentary cover share a number of significant geological similarities with sequences in the Bassarides Belt and Taoudéni Basin in the SW portion of the West African Craton.