Depósitos de olistostroma del Devónico (inferior?-medio?),Formación Los Sombreros, en la Quebrada de San Isidro, Precordillera de Mendoza

PERALTA, S.H.; HEREDIA, S.E.

La Plata

Congreso; XVI Congreso Geológico Argentino; 2005

Asociación Geológica Argentina

The siliciclastic, wackes and pelites interbedded, sequence outcropping at the San Isidro Creek, and classically named as Villavicencio Formation, are reinterpreted as an olistostromic (sedimentary mélange) succession 1.000 m thick, and reassigned to the Los Sombreros Formation, Lower-Middle? Devonian in age. These deposits show a typical deformational sinsedimentary framework, which includes in the lower part, 300 m thick, mainly siliciclastic slumps and slidings, derived from the Silurian? and Lower Devonian ?Villavicencio Formation? , which at the basal levels bears land plants remains referred to Barawanatia, which indicates Pridoli-Lower Devonian.  In the upper part, 700 m thick, this siliciclastic framework hosts allochthonous blocks, composed of graptolite-reach black shales (Climacograptus bicornis Biozone) and thin to medium layered limestones, from the underlying Empozada Formation (Middle-Upper Ordovician).  These olistostrome succession is believed as an extension in the Mendoza Precordillera, of the olistostrome deposits of the Los Sombreros Formation which recently has been recognized toward north, from the Río Jáchal section up to the southern end of the Tontal range, in the Los Sombreros creek, in addition of the eastern flank of the Sierra de La Invernada and El Palque and Los Ratones creeks, at the southern margin of the San Juan River.