Proveniência dos arenitos dos grupos Canindé, bacia cratônica do Parnaíba, por termocronologia e geocronologia em zircão detrítico.

Abstract

Before the most severe Late Paleozoic Ice Age, the Western Gondwana was affected by short-lived glaciations recorded in several intracratonic basins from Northern South Amer ica. The Famenian-Tournasian coastal marine successions exposed in the Sulamerican plat form represent a window of opportunity to unravel the different source lands using U-Pb ages of detrital zircon grains during the icehouse and greenhouse conditions. The Famenian Tournasian Cabeças Formation in the intraplate Parnaiba basin, Northern Brazil, represents a glaciomarine system of the ice contact delta developed at the Western Gondwana Margin. Preglacial deltaic deposits indicate two significant U-Pb age peak ranges of 768-448 Ma and 1175-937 Ma, suggesting drainage from the East of Western Gondwana. In contrast, U-Pb age peak ranges of 1998-1731 Ma and 1079-894 Ma show sources from the South supplying the northwestern glacier advance on the coastal-marine settings. During the initial greenhouse phase, the ice-melt deltaic system provided zircon ages of 1093-817 Ma, indicating the retak ing of the preglacial source lands. The sampling for age acquisition combined with precise paleoenvironmental interpretation offers, for the first time, high-resolution information that supports a most robust paleogeographic reconstruction of the Western Gondwana during the Late Paleozoic. Additionally, the use of Hf isotope and fission track proxies linked to a sys tematic morphological description, internal structure, and Th/U ratio applied to Mesoprotero zoic-Tonian detrital zircons, focused on the main detrital age spectra of glacial deposits, al lowed reveals the discrimination of competing sedimentary source land regions and recogniz ing detrital contributions from the provenance dynamic of ancient orogenic settings, such as the West Gondwana and Araçuai-West Congo orogens.