ARROYO LIMAY CHICO: UN EJEMPLO DE CAPTURA FLUVIAL EN LA CUENCA SUPERIOR DEL RÍO LIMAY (SE DE NEUQUÉN)

Limay Chico stream: an example of fluvial capture in the upper basin of the Limay River (SE of Neuquen). A process of stream piracy caused by the active retrograde erosion of Limay Chico stream -a tributary of Limay river- is des- cribed. It is located in the southern part of headwaters of the Alicura drainage basin, tributary of Collon Cura river. It is sup- posed that the increment of the headward erosion is related to the postglacial climatic conditions and a coetaneous deepening of the Limay river channel, a process expressed by modern and lower erosion terraces. Moreover the retrograde erosion was enhanced by the special location of the Limay Chico valley along an important line of structural weakness, the Limay Chico fault. The fluvial capture and the consequent diversion of the Alicura basin upper part showed previous favorable conditions: 1) the topographic lower disposition of Limay Chico stream and their base level; 2) its steeper slope and the location of Limay Chico valley along a zone of structural and litologicalk weakness; 3) transverse arrangement of the Alicura rivers headwaters; 4) its gentle slope and location of their basin and base level at a topographic higher level. Several wind gaps were recognized and were interpreted two probable elbows of capture and barbed pattern. Also the increment of discharge of Limay Chico stream caused in their basin local phenomena of static rejuvenation. It is suppose a close genetic relation between the lands- lides observed along the steep fault scarp promoted by the Limay Chico Fault and the postglacial climatic change and the local erosional deepening of Limay Chico valley. The slumps characterized by the coalescence of their scars, generated the irregu- lar and ruged landscape of the western side of Limay Chico valley. On the eastern valley slope the slumps reach minor expres- sion. Longitudinal profils and slopes of the analized streams are included.