Knickpoints as geomorphic markers of active tectonics: A case study from northeastern Sicily (southern Italy)

Abstract

Unsteady base-level fall at river mouths generates knickpoints that migrate as a transient upstream through the drainage network, climbing at the same rate as long as the fluvial erosion process follows a detachment-limited stream power law. Here we demonstrate unsteady and nonuniform rock uplift using knickpoints as geomorphic markers in streams draining the eastern flank of the Peloritani Mountains (northeast Sicily), the footwall of an ~40-km-long offshore northeast-southwest-oriented normal fault where the uplift is documented by a flight of mapped and dated Pleistocene marine terraces. Using slope-area analysis on the major streams, we project the tops of prominent knickpoints down to the coast, intersecting the marine terraces, thus providing an age for that specific knickpoint and the paleo-longitudinal profile. We model the migration rate of those dated knickpoints to locally solve for the parameters in the detachment-limited stream power law, and apply the results to model the age of other knickpoints with no clear connection to marine terraces. In summary, we demonstrate that the eastern Peloritani Mountains have been nonuniformly uplifted in an along-strike elliptical pattern, consistent with the general model for the footwall of an active normal fault. A calculation of the long-term erosion rate by the volume beneath the dated paleo-longitudinal profiles reveals a tight positive nonlinear relationship with the modeled normalized channel steepness (k sn). Our analysis provides a method for using knickpoints as geomorphic markers in steep, rapidly eroding landscapes that commonly lack datable river terraces.

Lithological and structural controls on river profiles and networks in the northern Sierra Nevada (California, USA)

“…In the upper reaches, where channels incise into bedrock, deviations from this shape can be attributed to a variety of causes, such as changes in lithology along the river's course (e.g., Duvall et al, 2004;Lecce, 1997;Phillips and Lutz, 2008;Pike et al, 2010), spatial variations in the delivery of coarse sediment to the channel (e.g., Finnegan et al, 2017;Hack, 1973;Hanks and Webb, 2006), and drainage capture (Fan et al, 2018). River profiles may also be modified by crustal deformation, thereby offering the potential for obtaining information about tectonic activity that might otherwise be difficult to acquire (e.g., Pavano et al, 2016).…”

Geomorphic evidence for active tectonic deformation in the coastal part of Eastern Black Sea, Eastern Pontides, Turkey

“…These methods have been used successfully in many countries and prove useful in the investigation of the current the activity of different areas such as in America, Iran, Spain, Italy and Turkey (e.g. Bagha et al, 2014;El Hamdouni, Irigaray, Fernández, Chacón, & Keller, 2008;Pavano, Pazzaglia, & Catalano, 2016;Troiani et al, 2014;Yıldırım, 2014). However, this is the first study to investigate the geomorphology and active tectonics of the Eastern Pontides.…”

Evolución del relieve en las fallas San Marcos, El Madroño y Las Vigas, norte de la junta triple del bloque Jalisco, México

“…Una vez detectados los knickpoints (Figura 2) se estimó la distancia que tienen éstos con respecto al frente montañoso, así como el área de drenaje de este último punto. La estimación del tiempo de retroceso de los knickpoints (t r ) se hizo para cada una de las fallas y con base en la ecuación usada por Pavano et al (2016) de tal forma que:…”

“…Dentro del análisis de los ríos, la propagación de los knickpoints, los cuales son geo-marcadores que pueden ser utilizados para cuantificar la edad de eventos tectónicos rápidos y con una escala temporal del orden de 10 1 a 10 7 años (e.g. Berlin y Anderson, 2007;Loget y van den Driesseche, 2009;Castillo y Lugo-Hubp 2011;Pavano et al, 2016), son clave para detectar la evolución del relieve tectónico ya que dichas formas son un resultado directo de un cambio en la tasa del levantamiento (Whipple y Tucker, 1999). A pesar de la demostrada aplicabilidad de este tipo de análisis para los grandes ríos de los relieves montañosos, pocos estudios han sido llevados a cabo en ríos de cuencas pequeñas (<100 km 2 ) con algunas excepciones (e.g.…”