Ductile deformation phases in eopalaeozoic formations in the Sierra de Ambargasta, Santiago del Estero and their stratigraphical significance

• Autores: Massabie, A.; Mutti, D.; Sanguinetti, A.; Cegarra, M.; Mozetic, M.
• Año de publicación: 1997
• Idioma: inglés
• Tipo de recurso: artículo
• Fuente: Rev. Asoc. Geol. Argent. 1997;52(2):209-218
• Materia: ductile deformation; lithostratigraphy; Paleozoic; Argentina
• Institución: Universidad Nacional de Buenos Aires. Facultad de Ciencias Exactas y Naturales

In the south of Santiago del Estero Province and in the north of Cordoba Province, the regional outcrops of Late Precambrian igneous-metamorphic basement show a N to NE tectonic trend which varies from the mainly N-S trend of the hills of central and southern Cordoba ranges. This ancient basement is dominated by granites and acidic porphyritic rocks which are best exposed in the Ambargasta Hills. Minor outcrops of medium-high grade metamorphic rocks (gneisses, schists, amphibolites and marbles) are better exposed in the central and southern. Cordoba ranges. In the main, this paper deals with unconformable overlying Eopalaeozoic folded quartzose sandstones, conglomerates and pelitic hornfels that compose the El Escondido and La Clemira formations, almost exclusively confined to the Ambargasta hills. The folded rocks are partially affected by contact metamorphism associated with intrusive granites dated as being of Late Cambrian (K/Ar 517± 15 Ma, intruding La Clemira Formation) and Carboniferous age (K/Ar 325±10 Ma, intruding in El Escondido Formation). The lithologic characteristics and location of these units, at the western boundary of the Chacoparana Basin, allow correlation with the subsurface marine Early Paleozoic units of that basin. However, tectonic studies by means of statistical mapping of ductile deformation structures (So; fold axis measurements), show the preservation of D2 (328) and D3 (18) deformations of Late Cambrian to Ordovician-Silurian age in El Escondido Formation, and recognized in several locations in the regional Late Precambrian metamorphic rocks of the Cordoba Pampean ranges. The stratigraphical position of the La Clemira and El Escondido Formations is restricted to the Cambrian-Early Ordovician, and could probably correlate with Las Brenas Formation or the Cambrian-Ordovician deposits of the Las Brenas Basin. A modification of the boundary of the Early Paleozoic Chacoparana and the Las Brenas basins is therefore suggested, extending them towards the southwest over the southern Santiago del Estero Hills.
Fil:Massabie, A. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.
Fil:Mutti, D. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.
Fil:Cegarra, M. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.