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vol.72 número1Alluvial architecture of reworked pyroclastic deposits in peri-volcanic basins: Castillo Formation (Albian) of the Golfo San Jorge basin, ArgentinaAnálisis estratigráfico y paleontológico del cretácico superior en la cuenca del golfo San Jorge: nueva unidad litoestratigráfica para el grupo Chubut índice de autoresíndice de assuntospesquisa de artigos
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Revista de la Asociación Geológica Argentina

versão impressa ISSN 0004-4822


TUNIK, Maisa A et al. Análisis petrográfico de areniscas de la formación castillo (Albiano) en la faja plegada de San Bernardo, cuenca golfo San Jorge, Argentina. Rev. Asoc. Geol. Argent. [online]. 2015, vol.72, n.1, pp.63-80. ISSN 0004-4822.

In order to understand the spatial variations in the sedimentary petrology of the Albian Castillo Formation at outcrops, sandstone samples obtained as part of fluvial channels in three areas of the San Bernardo fold belt were analyzed. These three geological and geographical regions show distinctive variation in the fluvial system and its facies arrangement, which is also evidenced by the petrography of the unit. Varieties of quartz, feldspar and lithic fragments were identified and described in order to analyze detrital modes. These analyses, carried out in the three different regions allowed to identify small-scale drainage networks of local character (region 2) where clastic composition reflects local sources, and also other areas with well integrated drainage networks of larger scale (region 4) that reflect large regional source areas. These differences can also be observed in provenance ternary plots, with a progressive evolution of the source areas from a transitional arc field, in which samples obtained from local drainage network fall near of the non-dissected arc field to samples belonging to regional drainage networks associated to a dissected arc in the provenance diagram. The detailed analysis of the framework and associated components showed that the observed secondary porosity in sandstones is due to the desegregation and dissolution of neovolcanic rock fragments. Development of secundary porosity is effective when the sandstones are cemented by heulandite-clinoptilolite zeolites or by rim-type clays.

Palavras-chave : Petrology; Diagenesis; Castillo Formation; Chubut Group; Golfo San Jorge Basin.

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