Dinámica fluvial y sedimentología del humedal Bañados del Atuel, Provincia de La Pampa, Argentina

LORENZO, FLORENCIA R.; ZÁRATE, MARCELO A.; MEHL, ADRIANA

San Miguel del Tucumán

Congreso; XX Congreso Geológica Argentino; 2017

Asociación Geológica Argentina

The ´Bañados del Atuel (BA)´ wetland is situated in the Atuel River (AR) terminal fluvial system, in central-west Argentina (~36°0´S-67°30?W, ~37°30´S-66°40?W), a complex geological setting including several morphostructural units (Cuyana basin, Chadileuvú Massif, La Pampa Central Block, San Rafael Block and Payunia). The AR basin is a sub-basin of the Colorado River fluvial system and it is in a misfit condition. The goal of this contribution is to analyze the geomorphological and sedimentological features of the BA wetland during the Late Holocene. For this purpose, previous studies were reviewed together with the analysis of satellite images and fieldwork consisting in the description of exposed stratigraphic sections and pits. Channels, floodplains, marshes and lagoons environments characterized the BA wetland fluvial network. The present active surface runoff zone in the BA wetland has a minimum expression because of a series of anthropic interventions in the basin (dams, man-made channels). The drainage network characterizes by a combination of channeled and unchanneled landforms; numerous channels with distributary pattern are product of nodal avulsions. Avulsions have been frequent in the AR terminal fluvial system and provided the necessary conditions for the formation and development of the wetland when the fluvial system was active. The transition between channelized flows and non-channelized flow occur in the wetland determining terminal floodouts. The alluvial plain, of low gradient (~ 0.55 m/km) and characterized by fine sediments (sand, silt and mud) would have developed during the Late Holocene.