A Silurian-Devonian marine platform-deltaic system in the San Rafael Block, Argentine Precordillera-Cuyania Terrane: Lithofacies and provenance

MANASSERO, M.J.; CINGOLANI, C.A.; ABRE, P.

The Geological Society of London, Special Publication

Geological Society

Año: 2009 p. 215 - 240

0305-8719

A Silurian-Devonian marine platform-deltaic system in the San Rafael Block, Argentine Precordillera-CUYANIA Terrane: LITHOFACIES AND PROVENANCE M. J. Manassero1*,  C. A. Cingolani 1, 2 & P. ABRE2 1Centro de Investigaciones Geológicas (UNLP-CONICET), Facultad de Ciencias Naturales y Museo, Universidad Nacional de La Plata, 1-644, (1900)-LA PLATA, ARGENTINA (manasser@cig.museo.unlp.edu.ar)* 2División Científica de Geología-Facultad Ciencias Naturales y Museo, Universidad Nacional de La Plata, Paseo del Bosque s/n, (1900)-LA PLATA, ARGENTINA (carloscingolani@yahoo.com and paulinabre@yahoo.com.ar) Abstract: The San Rafael Block is included as a part of the pre-Andean region, in the southern sector of the Argentine Precordillera-Cuyania terrane, within the western Gondwana margin. The Río Seco de los Castaños Formation (Upper Silurian-Lower Devonian) is one of its marine-siliciclastic ‘pre-Carboniferous units, interpreted as a distal to proximal silty platform-deltaic system. The dominant sedimentary processes were wave and storm action and the source areas were located to the east, close to the study area. The rocks are mainly immature arkosic sandstones showing both recycled orogen and continental block provenances. Conglomerate channels and an organic matter rich bed are described as relevant sedimentological characteristics. XRD analyses of the clay minerals from the sequences show very low-grade metamorphic conditions acted during the Lower Carboniferous. Geochemical analyses indicate moderate to strong weathering, and potassium metasomatism. Zr/Sc ratios lower than 22, no important enrichments of Zr, Th/Sc ratios, high Sc and Cr concentration and the Eu-anomalies indicate a provenance from an a less evolved Upper Continental Crust. TDM ages and εNd are within the range of the Mesoproterozoic basement and Palaeozoic supracrustal rocks from the Precordillera-Cuyania terrane. Probable sources, tectonic setting and land-sea interactions are discussed. Keywords: Argentine Precordillera-Cuyania terrane, San Rafael Block, Río Seco de los Castaños siliciclastic platform, Silurian-Devonian, provenance analyses.