Has focused denudation sustained active thrusting at the Himalayan topographic front?

Abstract

The geomorphic character of major river drainages in the Himalayan foothills of central Nepal suggests the existence of a discrete, west-northwest-trending break in rock uplift rates that does not correspond to previously mapped faults. The 40 Ar/ 39 Ar thermochronologic data from detrital muscovites with provenance from both sides of the discontinuity indicate that this geomorphic break also corresponds to a major discontinuity in cooling ages: samples to the south are Proterozoic to Paleozoic, whereas those to the north are Miocene and younger. Combined, these observations virtually require recent (Pliocene-Holocene) motion on a thrust-sense shear zone in the central Nepal Himalaya, ϳ20-30 km south of the Main Central thrust. Field observations are consistent with motion on a broad shear zone subparallel to the fabric of the Lesser Himalayan lithotectonic sequence. The results suggest that motion on thrusts in the toe of the Himalayan wedge may be synchronous with deeper exhumation on more hinterland structures in central Nepal. We speculate that this continued exhumation in the hinterland may be related to intense, sustained erosion driven by focused orographic precipitation at the foot of the High Himalaya.

The Euphrates-Tigris-Karun river system: Provenance, recycling and dispersal of quartz-poor foreland-basin sediments in arid climate

“…9). Channel steepness and erosion rates are relatively high along the southern flank of the Bitlis Massif, but remain still markedly lower than along Alpine or Himalayan neometamorphic axial belts (Wobus et al, 2003;Korup and Schlunegger, 2009). …”

Three‐dimensional numerical models with varied material properties and erosion rates: Implications for the mechanics and kinematics of compressive wedges

“…The high erosion rates maintain material removal and deformation along the Alpine Fault [Koons, 1990;Beaumont et al, 1992]. Many recent studies also suggest that focused erosion along the Himalayan front also may have an effect on the nature and locus of the deformation [e.g., Thiede et al, 2004Thiede et al, , 2005Wobus et al, 2003Wobus et al, , 2005, although other authors argue against erosion playing such as controlling role [e.g., Burbank et al, 2003].…”

Testing the effects of topography, geometry, and kinematics on modeled thermochronometer cooling ages in the eastern Bhutan Himalaya

“…The combinations of velocities, radiogenic heat production values, and flexural models tested are in Table 3. A constant velocity of 17.3 mm yr −1 using an MCT initiation age of 23 Ma was tested to determine if a generalized long-term rate of shortening can adequately reproduce (Bilham et al, 1997;Larson et al, 1999;Banerjee and Bürgmann, 2002;Zhang et al, 2004;Bettinelli et al, 2006;Banerjee et al, 2008) and long-term rates of shortening for the Himalaya (DeCelles et al, 2001;Lavé and Avouac, 2000;Long et al, 2011b). In Bhutan, variable rates of shortening have been proposed based on the integration of shortening estimates from balanced cross sections with thermochronometer data.…”