The Neoproterozoic glacial record in the Río de la Plata Craton: a critical reapraissal

PAZOS P. J.; SANCHEZ-BETTUCCI L.; LOUREIRO J.

Special Publication of the Geological Society

Geological Society of London

Lugar: Londres; Año: 2009 vol. 294 p. 343 - 364

0305-8719

Neoproterozoic glacial successions have been described in South America, but the glacial deposits of the Rı´o de la Plata Craton have been neglected in previous studies addressing the global distribution of glacially influenced successions. The Rı´o de la Plata Craton contains Neoproterozoic glacial deposits in the Sierra del Volca´n Formation (Tandilia System, Argentina),glacial influenced deposits in the Playa Hermosa and Zanja del Tigre formations (Dom Feliciano Belt, Uruguay) and suspected glacially influenced deposits in Passo da Areia (Sa?o Gabriel block, Brazil). The Tandilia System glacial record includes diamictites, dropstones and rhythmites deposited in glaciomarine conditions in a tectonically stable depositional setting. The Dom FelicianoBelt includes a thin section with ice-rafted clasts in carbonates and a thicker section containing diamictites, rhythmites, outsized clasts and deformed beds in a volcano-sedimentary succession.The Sao Gabriel block occurrence deserves more attention to confirm any glacial influence in the fine-grained part of the succession. Glaciation is considered to be contemporaneous withthe Gaskiers glaciation (580 Ma), with the exception of the carbonates with dropstones that may represent a previous event correlative with one of the glaciations described in the Kalahari Craton, prior to Kalahari?Rı´o de la Plata assembly in the proto-western Gondwana margin.