Revista de la Asociación Geológica Argentina
versión ISSN 0004-4822
GALLI, Claudia Inés et al. Provenance of the Payogastilla Group (Cenozoic), Calchaquí river, Salta Province. Rev. Asoc. Geol. Argent. [online]. 2011, vol.68, n.2, pp. 261-276. ISSN 0004-4822.
Cenozoic deposits comprising the fluvial sediments of Payogastilla Group (Middle Eocene-Late Miocene) were studied in the southern portion of the Calchaquí Valley, Salta province. The strata are well-exposed on both banks of the Calchaquí river and comprise 5,400 m of clastic deposits, defined, from base to top, by Los Colorados, Angastaco, Palo Pintado and San Felipe formations. Mineralogic, petrographic, geochemical and X-ray diffraction analyses of the constituent facies of Los Colorados, Angastaco and Palo Pintado formations are described, including their provenance, derived from paleocurrent studies. The main sandstone facies component is characterized by quartz grains; other detrital components are potassium feldspar, altered plagioclase, perthite and abundant mica. The compacted and matrix supported conglomerate deposists exhibit clasts mostly of pegmatite, granite, quartz, slate-clay, gneiss and migmatite. These data are associated with the results of major and trace elements with a similar affiliation to the rocks of the eastern edge of the Puna (Eruptivo Oire Complex) and Sierras Pampeanas. X-ray difracction analysis of clay samples from the Palo Pintado formation reveal illite and montmorillonite, which are interpreted to be of detrital origin, while the saponite has been generated by weathering in a humid-temperate climate. Compositional characteristics and paleocurrent data suggest primary sediment contribution from the cumbres de Luracatao and sierra de Vázquez, as well as from the Runo and Durazno ranges, sierra de Quilmes and Cumbres Calchaquíes and, to a lesser extent, from the cerro Colorado, throughout the middle Eocene to late Miocene.
Palabras llave : Payogastilla Group; Petrographic analysis; Geochemistry and x-rays difracction.