GEOMORPHIC AND STRATIGRAPHIC MODELING OF INTRAMONTANE BASINS, WITH AN EXAMPLE FROM THE TORO BASIN IN NW ARGENTINA

Intramontane basins may act as important sediment storage areas, serve as recorders of the history of deformation, and record syn-tectonic deposition. In this contribution, we use a set of Geomorphic Transport Laws (GTLs), in which rivers incise bedrock and sediments are deposited in the adjacent basins, to understand those conditions that cause intramontane basins to become internally drained, and those that promote headward erosion and recapture of such basins. We find that the propensity of these intramontane basins to become internally drained is mainly determined by rock uplift rates within areas downstream of the basins, and likely depends to a lesser degree on climate (represented by discharge) and the resistance of bedrock to fluvial incision in the downstream channel reaches. Recapture of isolated intramontane basins requires a change in rock uplift rate or climate; the likelihood of intramontane basin reintegration with the downstream fluvial system depends also on the magnitude of change of these variables and the resistance of bedrock to fluvial incision within the downstream reaches of the channels. While these types of simulations quantify changes in the elevations of the basins and channels, we can track the erosion and depositional products in the model over time, allowing us to model the stratigraphy that might be expected for a set of tectonic and climatic scenarios affecting a these basins.

We apply this model of intramontane basin formation to the Toro Basin in the Eastern Cordillera of NW Argentina, where the history of basin filling and uplift of the surrounding ranges is known from geologic observations. Using rates of basin filling, uplift rates of the surrounding ranges, and discharge computed from current, high-resolution precipitation measurements and digital elevation models, we find that our model successfully predicts the conditions under which the Toro Basin likely became internally drained. We suggest that similar approaches can be applied to other intramontane basins to provide a quantitative understanding of how tectonic and climatic processes may affect the geomorphic and stratigraphic development of these features.