Sedimentação siliciclástica e proveniência do grupo Alto Paraguai (neoproterozóico-cambriano), borda Sul do Cráton Amazônico e faixa Paraguai Norte, estado do Mato Grosso.

Abstract

The Neoproterozoic-Cambrian Alto Paraguai Group exposed in the southern Amazon Craton and the northern Paraguay Belt, western-central Brazil, represents a 2,400m thick siliciclastic succession that succeed the carbonate platform sedimentation deposited after the last Cryogenian glaciation (635 Ma). The Alto Paraguai Group consists of Raizama (fine to coarse grained sandstones, conglomerates, mudstones, pebbly mudstones and secondary chert), Sepotuba (dolomites, stromatolites, mudstones and fine to medium grained sandstones) and Diamantino (mudstones and fine to medium grained sandstones) formations. Outcropbased facies and stratigraphic analysis in combination with provenance studies using detrital zircon U-Pb dating, allowed understanding the lithostratigraphy and the depositional history of the Alto Paraguai Basin. The depositional model include the progradation of a fluvialwave-tide- and storm-dominated coastal region (upper member of the Raizama Formation) onto a shallow to moderately deep storm-influenced marine platform, locally influenced by debris flow (lower member of the Raizama Formation). Afterwards, the last transgressive event in the Paraguai Basin generated tidal flat-sabkha setting in the shallower portions of the basin to the west (lower member of the Sepotuba Formation) and a storm-dominated marine platform in the central and eastern portion of the basin (upper member of the Sepotuba Formation). The progression of the Pan-African-Brasilian orogenesis resulted in the confinement of the Sepotuba Sea as a foredeep sub-basin, against the edge of the Amazon Craton. These restricted lake/sea was filled with turbidites deposits (lower member of Diamantino Formation), lacustrine sediments (middle member of the Diamantino Formation) and progradational deltaic front deposits (upper member of the Diamantino Formation). This sedimentation was supplied by source areas of 600 to 500 Ma, located in the southeast and east of the basin, related to the Brasilia Belt and the Paraguay orogen. This stage represents the final amalgamation of Western Gondwana, marked by the closure of the Neoproterozoic Clymene Ocean between the Amazon Craton and Central Gondwana, generating the northern Paraguay Belt.