Significado estratigráfico y tectónico de los bloques resedimentados cambro-ordovícicos de la Precordillera Occidental, Argentina

BENEDETTO, J.L.; VACCARI, N.E.

ESTUDIOS GEOLOGICOS

Museo Nacional de Ciencias Naturales

Lugar: Madrid; Año: 1992 vol. 48 p. 305 - 313

0367-0449

Rocks belonging to the Early Paleozoic Los Sombreros Formation crop out on the eastern flank of the Sierra de Yerba Loca, along the Rio Jachal section. This Formation consists of black shales and turbidites with interbedded limestone boulders near the base of the section, one of them up to 200 m long and 30 m thick. Boulders yield both early Cambrian trilobites and early Ordovician conodonts. Near the top, a thick sequence of dark gray marls and limestones contains an early Middle Cambrian trilobite fauna which is overlain by limestones and calcareous turbidites containing early Llanvim graptolites and conodonts. On the basis of paleontological and sedimentological evidences this sequence can be interpreted as a series of submarine gravity slides interbedded within a dominantly turbiditic sequence. The Cambrian-early Ordovician precordilleran carbonate platform servedas the source for much of the sediment which was redeposited on the slope. Then, deposition of the early Ordovician Los Sombreros Formation could be related to uplift and erosion of the platform margin and steepening of the slope during the late Arenig-early Llanvim.