Do river profiles record along‐stream variations of low uplift rate?

Abstract

[1] Spatial variations of gradients in landscapes may be used to identify and quantify recent deformation. The problem with doing this is to determine whether tectonic or climatic forcing is responsible for these variations, especially for low uplift rate environments ((1 mm yr À1 ) where climate changes may have erased tectonic features. We evaluate the respective contribution of low uplift rate ($0.1 mm yr À1 ) and Pleistocene climate oscillations on gradient variations of two comparable river profiles crossing different uplift zones in the southern Upper Rhine Graben. We compare the observed points of discontinuity in river profile (knickpoints) and convex portions (knickzones) with those predicted by a detachment-limited model that includes stochastic short-term and cyclic long-term variations in climate, a bedrock detachment threshold and rock uplift. The detachment-limited model is chosen as it predicts the development of persistent knickpoints. Differing values of the shear stress exponent, erosion threshold, climate variability and uplift pattern have been checked. Our modeling suggests that climate changes had no significant effects on profiles and that anomalies are more likely due to anticline growth. This surprising result arises from the combination of a very low regional uplift rate and the detachment-limited assumption. The detachment-limited model implies an upstream propagation of knickpoints and knickzones generated by uplift at the outlet during dry climate periods of low erosion. The greater the uplift rate, the larger the variations in river bed elevation. Thus, for high uplift rate, knickpoints and knickzones generated by climate oscillations are more likely to hide tectonic features. This result seems counterintuitive because it suggests that tectonic knickzones will be better preserved in low uplift rate environments, provided that the lithology is homogeneous.Citation: Carretier, S., B. Nivière, M. Giamboni, and T. Winter (2006), Do river profiles record along-stream variations of low uplift rate?,

Deciphering neotectonics from river profile analysis in the karst Jura Mountains (northern Alpine foreland)

“…Folding and thrusting took place between about 14 and 3.3 Ma according to stratigraphic and paleontological evidences (Becker 2000;Schmid 2006, 2007 andreferences therein). However, geomorphological evidence suggest that more recent deformations (i.e., Pleistocene to Holocene) occured along the northernmost frontal thrusts of the Jura (Nivière and Winter 2000;Giamboni et al 2004b;Carretier et al 2006;Nivière et al 2006;Schmid 2006, 2007;Madritsch et al 2010b;Molliex et al 2011). These authors highlight a Plio-Pleistocene N-S horizontal shortening in the external part of the Jura with an average uplift velocity of *0.05 mm/year at the front.…”

“…Moreover, quantification of the recent tectonic activity in slowly deforming mountainous environments remains challenging because deformation markers have been potentially modified or erased by climatically-driven surface processes over the Quaternary period (Whipple 2001;Carretier et al 2006).…”

Response of drainage systems to Neogene evolution of the Jura fold-thrust belt and Upper Rhine Graben

“…In the sundgau and Ajoie, the sundgau Gravels are involved in the frontal folds of the Jura Mountains. Moreover, there is evidence for Quaternary changes in drainage patterns and anomalies in river gradients, as well as for the deformation of terraces, indicating late stage compressional deformation of the Mulhouse High (Nivière & Winter 2000;Giamboni et al 2004a, b;carretier et al 2006) and the Ajoie (brail- sundgau Gravels (Ustaszewski & schmid 2006) and presumably continued to grow during the late Pliocene and Quaternary compressional deformation of the Mulhouse High.…”

Detection and analysis of morphotectonic features utilizing satellite remote sensing and GIS: An example in SW Jordan

“…These anomalies are commonly referred to as knickzones or knickpoints. The latter are points of discontinuity or steep segments in a river profile that are usually a response to climate changes, stream power, lithological variability, or tectonic distortions (Hack, 1973;Seeber and Gornitz, 1983;Miller, 1991;Alexandrowicz, 1994;Zaprowski et al, 2001;Duvall et al, 2004;Bishop et al, 2005;Carretier et al, 2006;Hayakawa and Oguchi, 2006;Larue, 2007). The study of longitudinal profile anomalies can thus give information about lithological and/or tectonically influence on parts of the drainage system if other factors such as climate and stream power can be discarded.…”