Investigation of the relationships between basin morphology, tectonic uplift, and denudation from the study of an active fold belt in the Siwalik Hills, central Nepal

Abstract

Abstract. The present study investigates correlations between an extensive range of geomorphic properties that can be estimated from a digital elevation model and the uplift rate on geological timescales. The analysis focuses on an area in the Siwalik Hills (central Nepal), where lithology and climate can be considered as uniform. This area undergoes rapid tectonic uplift at rates of up to 15 mm yr -•, which are derived from the geometric pattern of a faultbend model of fold growth. The selected geomorphic properties can be divided in two categories, depending on whether or not the vertical dimension is taken into account. None of the planar properties are significantly correlated to uplift rate, unlike those that include the vertical dimension, such as the mean elevation of basins, hypsometric curve, and hypsometric integral, and relief defined by the amplitude factor of length scaling analysis. Correlation between relief and uplift rate is observed for all length scales of topography shorter than 600 m, which suggests that all orders of the streams are able to adjust to the tectonic signal. Simple mass balance considerations imply that the average elevation is only 10% of surface uplift, suggesting that a dynamic equilibrium has been reached quite rapidly. Using a simple two-process model for erosion, we find that fairly high diffusion coefficients (order of 10 m 2 yr -•) and efficient transport of the material by rivers are required. This unusually high value for mass diffusivity at small length scales may be obtained by either a very efficient linear diffusion or by landsliding. Actually, both processes may be active, which appears likely given the nature of the unconsolidated substratum and the favorable climatic conditions. Local relief in the study area may therefore be used to predict either uplift or denudation, but the prediction is calibrated only for that specific climatic and lithologic conditions and cannot be systematically applied to other contexts.

Natural experiments in landscape evolution

“…Heimsath et al, 1997;Cyr and Granger, 2008), fault geometry (e.g. Hurtrez et al, 1999;Kirby and Whipple, 2001), and fluvial strath terraces (e.g. Pazzaglia et al, 1998;Berryman et al, 2000;Avouac, 2000, 2001;Pazzaglia and Brandon, 2001;Brocard et al, 2003;Tomkin et al, 2003;Brocard and van der Beek, 2006).…”

“…For example, thermochronologic data from a number of the world's active mountain ranges imply that the total vertical displacement of rock is much larger than the mountain-range relief, which implies that the majority of uplifted rock has been eroded during the lifetime of the active structure (e.g. Hurtrez et al, 1999;Tippett and Hovius, 2000). While this does not necessarily imply that topography itself is steady and unchanging (see, e.g.…”

“…One example of this is a long-lived fault-bend fold moving over a curving ramp, where the rate of rock uplift in the hangingwall (relative to the footwall) depends on the rate of thrust propagation and on the local dip of the fault plane (e.g. Hurtrez et al, 1999;Miller et al, 2007). Steady, non-uniform landscapes may also be found in transient settings where erosion rates are evolving in both space and time, but temporal variations are relatively subtle over the time scale required to lower the land surface by a depth comparable to the thickness of the soil (e.g.…”

Cenozoic river profile development in the Upper Lachlan catchment (SE Australia) as a test of quantitative fluvial incision models

“…Drainage area was obtained from a 9 arc sec digital elevation model (DEM) provided by the Australian Surveying and Land Information Group (AUSLIG), using standard drainage extraction techniques [cf. Hurtrez et al, 1999]. Although this procedure also allowed us to generate valley long profiles from the DEM data, we chose to use the channel profiles as digitized by Goldrick [1999] from the topographic maps because the latter are much more accurate.…”

Development of experimental landforms by rainfall erosion and uplift

“…10 4 10 5 : W. M. Davis e.g., Davis, 1889Davis, , 1899 cf., Chorley et al, 1984;Thorn, 1988Paine, 1985 G. K. Gilbert e.g., Gilbert, 1877 Hack 1960 dynamic equilibrium e.g., Adams, 1980;Burbank et.al., 1996;Hurtrez and Lucazeau, 1999;Pazzaglia and Brandon, 2001 e.g., Howard, 1988;Phillips, 1992;Pazzaglia and Knuepher, 2001 geomorphic processes e.g., Schumm and Lichty, 1965;Allen, 1974;Renwick, 1992 relaxation time reaction time e.g., Renwick, 1992Trimble, 1977 e.g., Schumm, 1963;Arnert, 1970 e.g., Kooi and Beaumont, 1996;Willett et al, 2001 Hasbargen and Paola, 2000 , Schumm et al, 1987Schumm et al, 1987Hooke, 1968 hardware model; Mosley and Zimpher, 1978Chorley, 1967Mosley and Zimpher, 1978 kinematic model dynamic model Froude number fall velocity incipient motion Schumm et al 1987 e.g., Hasbargen and Paola, 2000;Crave et al, 2000;Hancock and Willgoose, 2001;Bonnet and Crave, 2003;Lague et al, 2003;Pelletier, 2003;Turowski et al, 2006;Graveleau and Dominguez, 2008 steady state equilibrium; Chorley and Kennedy, 1971 Allen, 1974 …”