Glacially influenced sedimentation of the Puga Formation, Cuiabá Group and Jacadigo Group, and associated carbonates of the Araras and Corumbá groups, Paraguay Belt, Brazil
Carlos J. S. Alvarenga, Paulo C. Boggiani, Marly Babinski, Marcel A. Dardenne, Milene F. Figueiredo, Elton L. Dantas, Alexandre Uhlein, Roberto V. Santos, Alcides N. Sial, Roland Trompette, 2011. "Glacially influenced sedimentation of the Puga Formation, Cuiabá Group and Jacadigo Group, and associated carbonates of the Araras and Corumbá groups, Paraguay Belt, Brazil", The Geological Record of Neoproterozoic Glaciations, Emmanuelle Arnaud, Galen P. Halverson, Graham Shields-Zhou
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Discontinuous exposures of diamictite (>1000 km) termed the Puga Formation (Fm.) and interpreted as being related to a late Cryogenian glacial event are known in the Paraguay Belt (Brazilian–Pan-African Orogeny) and part of the Amazon craton and Rio Apa Block. These diamictite units and a mixed assemblage of sandstone, conglomerate and claystone were first named the Jangada Group. Recent interpretations have shown that the diamictite of the Puga Formation passes laterally into metasediments of the Cuiabá Group, interpreted as glacially influenced turbidites. The correlative Jacadigo Group in the southern Paraguay Belt includes a thick succession of banded iron formation (BIF) bearing large boulders that have been interpreted as recording glacially influenced sedimentation. The diamictite of the Puga Fm. is overlain by two different carbonate-bearing successions, the Corumbá Group (Cadieus, Cerradinho, Bocaina, Tamengo and Guaicurus formations) in the south and the Araras Group (Mirassol d'Oeste, Guia, Nobres formations) in the north. Evidence of glaciation in the Puga Fm. consists of striated and faceted pebbles and blocks, and dropstones in the turbidites. Sedimentary and geochemical data from the associated carbonate reinforce the interpretation of a glacial origin. C, O and Sr isotope data from the northern Paraguay Belt are consistent with the proposed late Cryogenian age for the Puga Fm. sedimentation.
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In recent years, interest in Neoproterozoic glaciations has grown as their pivotal role in Earth system evolution has become increasingly clear. One of the main goals of the IGCP Project No. 512 was to produce a synthesis of newly available information on Neoproterozoic successions worldwide similar in format to Hambrey & Harland’s (1981) Earth’s pre-Pleistocene Glacial Record. This Memoir therefore consists of a series of overview chapters followed by site-specific chapters. The overview chapters cover key topics including the history of research on Neoproterozoic glaciations, identification of glacial deposits, chemostratigraphic techniques and datasets, palaeomagnetism, biostratigraphy, geochronology and climate modelling. The site specific chapters for 60 successions worldwide include reviews of the history of research on these rocks and up-to-date syntheses of the structural framework, tectonic setting, palaeomagnetic and geochronological constraints, physical, biological, and chemical stratigraphy, and descriptions of the glaciogenic and associated strata, including economic deposits.