Landscape Response to Lateral Advection in Convergent Orogens Over Geologic Time Scales

Abstract

Convergent orogens exhibit high elevations and relief, features characteristic of active rock uplift, the latter influencing normalized channel steepness (Ksn). In systems with significant horizontal displacement, Ksn values and interfluves are elevated over a region of tens of kilometers and gradually decline in the direction of rock advection. To evaluate potential relationships between elevated Ksn, a gradual decline in interfluve elevation (i.e., tapered topography), and lateral advection, we integrated kinematic models that simulate advection over a midcrustal ramp with a 2‐D surface processes model. Varying convergence rate, bedrock erodibility, and ramp angle, we tracked topographic evolution over time. The process of advection through the region of active rock uplift above a midcrustal ramp is preserved in the geomorphic record through transient legacy landscapes characterized by (i) high‐relief, advection‐parallel interfluves, (ii) tapered topography, (iii) elevated and gradually declining Ksn values, and (iv) higher Ksn in trunk relative to tributary streams likely reflecting the influence of increased sediment flux, elevated interfluves, and changes in drainage area. The width of legacy landscapes provides a minimum constraint on the total lateral displacement, controlled by the duration of ramp activity and the rates of advection and erosion. The development of legacy landscapes is facilitated by spatial variations in flow convergence that occur in a 2‐D setting but are not captured in idealized 1‐D approaches. The presence of elevated Ksn and high relief, advection‐parallel interfluves beyond the region of active rock uplift likely reflects the horizontal advection component inherent to convergent orogenic systems.

Influence of orographic precipitation on the topographic and erosional evolution of mountain ranges

“…It is probable that these variations generate variations in catchment-mean denudation rates, in a way that still needs to be studied. The lack of lateral tectonic advection in our simulation must also be pointed out, as this process likely controls the evolution of the landscape and the position of the drainage divide (Willett et al, 2001;Eizenhöfer, McQuarrie, Shelef, & Ehlers, 2019). 6.…”

The destiny of orogen-parallel streams in the Eastern Alps: the Salzach–Enns drainage system

“…Then a divide that is stable in an absolute frame is mobile in the moving system and thus asymmetric with a sharp contrast. The conditions for the development of such stable divides were investigated by Eizenhöfer et al (2019) by computing the crustal velocity governed by over-thrusting at a flat-ramp-flat geometry and modelling the response of the drainage system. Beyond this, contrasts in precipitation may cause sharp asymmetries at drainage divides because the pattern of precipitation is influenced by the topography, although the control of precipitation on the geometry of river channels is still debated (e.g.…”

“…As a consequence of the horizontal and vertical motion of the crust, drainage systems are also advected (Clark et al, 2004;Miller and Slingerland, 2006;Stüwe et al, 2008;Castelltort et al, 2012;Kirby and Whipple, 2012;Miller et al, 2012;Fox et al, 2014;Goren et al, 2015;Yang et al, 2016;Guerit et al, 2018;Eizenhöfer et al, 2019). However, rivers are not just passive markers of crustal deformation; they also adjust their channel slopes to the contributing drainage area, uplift rate and bedrock properties until longitudinal channel profiles are graded and long-term erosion rates are in balance with uplift rates (Kooi and Beaumont, 1996;Whipple, 2001;Willett et al, 2001;Goren et al, 2014;Robl et al, 2017b).…”

Transport-limited fluvial erosion – simple formulation and efficient numerical treatment

“…It is a lumped parameter subsuming all influences on erosion other than channel slope and catchment size. So it is not only a property of the rock, but also depends on climate in a nontrivial way (e.g., Ferrier et al, 2013;Harel et al, 2016). However, it just defines how steep rivers will become at a given uplift rate, so reasonable values can be found, e.g., by analyzing river profiles in situations where estimates of the uplift rate are available.…”