Abstract

PAYROLA BOSIO, Patricio Augusto; DEL PAPA, Cecilia; HONGN, Fernando  and  POWELL, Jaime. Stratigraphy of Luracato Valley (Calchaquí Valley, Norwestern Argentina): New proposal. Rev. Asoc. Geol. Argent. [online]. 2010, vol.67, n.3, pp.309-318. ISSN 0004-4822.

During Lower Cretaceous-Eocene the Salta Group rift basin was developed in northwest Argentine, showing well-defined synrift (Pirgua Subgroup) and postrift (Balbuena and Santa Barbara Subgroups) stages. Then and superimposed to the rift, broad foreland basin was generated. The Payogastilla Group represents the Andean synorogenic filling in the Calchaquí Valley; its base records the Paleogene deformation and inversion tectonics of this zone of the Eastern Cordillera. The Luracatao valley (western branch of the Calchaquí Valley) preserves a thick sedimentary sequence designed as the Luracatao Formation of possible Oligocene age in previous regional maps. This paper presents a redefinition of the stratigraphy of the Luracatao valley based on field works of regional scale, stratigraphic logs and detailed structural mapping. The analyses of sedimentary facies and facies association and the identification of stratigraphic unconformities allow identifying the units of the Santa Bárbara Subgroup (Mealla Formation, Maíz Gordo Formation and Lumbrera Formation) and of the Payogastilla Group (Quebrada de los Colorados Formation) among the levels previously assigned to the Luracatao Formation. Special importance has the identification of an unconformity between Santa Bárbara Subgroup and Quebrada de los Colorados Formation that integrated to paleontological data allow us interpret this unconformity as the record of the first Cenozoic deformation events. Based on the redefinition of the Luracatao Valley stratigraphic column, this paper proposes to replace the Luracatao Formation by the respective units identified.

Keywords : Valle de Luracatao; Quebrada de los Colorados Formation; Foreland basin.

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