The Andrelândia basin, a Neoproterozoic intraplate continental margin, southern Brasília Belt, Brazil

Abstract

The Andrelândia succession comprises six lithofacies associations, from base to top, represented by: Al- paragneiss; A2- paragneiss, quartzite and schist; A3- quartzite; A4- grey phyllite/schist; A5- biotite schist/gneiss; A6- paragneiss, metachert and calc-silicate rocks. Amphibolite bodies are common in the Al, A2 and A6 associations. They represent continental and oceanic tholeiitic magmatism generated during the basin evolution. The vertical and horizontal distribution of these lithofacies suggest transgressive and regressive depositional systems of common intraplate continental margin paleoenvironments, probably including continental (Al), coastal plain-platform (A2, A3, A4, A6), submarine fan and basin plain deposits (A5.A6). The lithofacies associations and the mafic magmatism also reflect different stages of basin evolution from rifting (Al) to proto-oceanic (A2, A6) and mature continental margin stages (A3, A4, A5, A6). This continental margin had its paleocoastline oriented NW-SE and depocenter to WSW as indicated by the regional distribution of the quartzitic and politic lithofacies. The basin opening is related to a world-wide taphrogenic event that started at circa 1,000 Ma. The Andrelândia Basin comprises the intraplate continental margins between the Sao Francisco plate and the Parana Block. The basin closure took place in two subsequent collisional stages during the Brasiliano Orogeny that resulted in the Brasilia Belt and the Central Segment of the Ribeira Belt.