El sistema de plataforma fangosa-delta (Silúrico-Devónico) de la Formación Río Seco de los Castaños, Bloque de San Rafael, Mendoza

• Autores: Manassero, Marcelo Jorge; Cingolani, Carlos Alberto; Uriz, Norberto Javier
• Año de publicación: 2006
• Idioma: español castellano
• Tipo de recurso: documento de conferencia
• Materia: Geología; Formación; Sedimentos; Estratigrafía
• Institución: Universidad Nacional de La Plata

The Rio Seco Fm is a distal (below wave base) to proximal silty-siliciclastic marine platform-deltaic system due to the relatively scarce diversity of environments, the dominance of fine to medium sedimentary grain sizes, the lack of tractive sedimentary structures, and the important thickness of the beds associated also to local gravity flow proceses. In this unit, the sedimentary input was continuos, due to the absence of internal discontinuities, the basin was widespread, and the paleo-slope was very small (less than 1%). The dominant processes acting on this environment, were wave and storm action, prevailing the settling of fines over the tractive processes. The source areas were located to the east, close to the study area due to the abundance of micas within the framework of the sandstones. The presence of plant debry, in the Atuel and Lomitas Negras sections suggests also, closer vegetated areas. The hidraulic regimes were moderate and the sea level changes in the sequence have generated very few sedimentary unconformities, but widespread lateral bed continuity. The sandstone petrography and the scanning electron microscopy (SEM) data show mainly inmature arkosic wackes with both a recycled orogen and continental block provenances The trace fossil data with shallower ichnofacies to the east and Nerites to the west is coherent with the lithofacies interpretation of deeper sectors of the basin located to the west. Two new lithofacies: conglomerate channels and an organic matter rich bed are described here as new relevant sedimentological characteristics. Similar siliciclastic environment interpreted as overfeed sedimentary system with great thickness (high sedimentary rates) and low textural maturity have been described by other authors within the Precordillera Terrain for both the Silurian and the Devonian.
Centro de Investigaciones Geológicas