River Longitudinal Profile Analysis as Indicator of Neotectonic Activity. A Case Study: The El Carrizal Creek Basin, Comechingones Ranges, Eastern Pampean Ranges, San Luis, Argentina

The Carrizal creek basin is located in the easter zone of the province of San Luis, (Argentina) and it drains the Comechingones Ranges (Eastern Pampean Ranges). Surveys along the Comechingones Ranges front have demonstrated that active Quaternary faults are located at the western margin of piedmont foreland. In this study, we analyze the longitudinal profile variations of the El Carrizal Creek and eight tributaries which drain the western slope of the Comechingones Ranges. We studied the distribution of knickpoints/knickzones, the gradient variations, concavity index and models of the longitudinal profiles, using simple mathematical functions in order to explore the signal of tectonic activity. According to the preceding analysis and the stratigraphic and geomorphological evidence, in this study, we consider that the tectonic aspects explain the major anomalies in the El Carrizal creek longitudinal profile. Subordinately, the climate has controlled the rate of erosion. Based on the foregoing, knickpoints found in the rivers analized in the El Carrizal Creek basin provide evidence of the presence and tectonic activity of the La Aguada Ranges and the Comechingones and La Aguada fault. This last structure, according to the stratigraphy and geomorphology of the area would have registered two seismic events during the Quaternary.