Tectonic from topography – a case study in Tibetan Plateau

Yang Wan-Huei 

Abstract

Many believe that mass redistribution by erosion represents a governing force in the tectonic evolution of orogenic systems and the steepest landscapes are associated with regions of rapid rock uplift.Based on these theories, we think that parameterization of landscape morphology could reveal meaningful geological information in the active tectonic regions. In these papers, the authors (Wobus et. al., 2006 & Kirby et. al., 2003) used stream power incision model to evaluate the channel steepness indices, which reveal the spatial distribution of bedrock channel gradients in longitudinal channel.Kirby et. al. (2003) studied the area adjacent to the SichuanBasin in an effort to assess the degree and nature of active deformation along this margin of the Tibetan Plateau. In practice, the channel steepness indices can be affected by variations in substrate erodibility, sediment flux, precipitation, and transient changes in profile shape, and it is difficult to distinguish which part affect the channel steepness indices most.The authors tried to eliminate factors using additional informations, for example: by comparing the steepness indices and the map of lithologic variations, the result reveals that lithology has only a limited influence on channel gradient in this field area. According to the channel steepness indices, channels of all size are steeper near the plateau margin and there is no systematic relationship between steepness indices and upstream drainage area. The result reflected that the variations of channel steepness indices were not affecting by the area spatial anamolies but tectonic controls it most.They argued that these systematic changes of channel steepness indices are not readily explained as a consequence of increased sediment flux or of orographic precipitation. From these evidences, the authors concluded that steep channel profiles along the topographic front of the plateau reflect active differential rock uplift between this region and the foreland.

Reference

Wobus, C., K. X. Whipple, E. Kirby, N. Snyder, J. Johnson, K. Spyropolou, B. Corsby, and D. Sheehan (2006), Tectonics from topography: Procedures, promise, and pitfalls, Geol. Soc. Am. Spec., 398, 55-74.

(Abstract)(Full text)

Kirby, E., and K. X. Whipple (2003), Distribution of active rock uplift along the eastern margin of the Tibetan Plateau: Inferences from bedrock channel longitudinal profiles, J. Geophys. Res., 108(B4), 2217, doi:10.1029/2001JB000861.

(Abstract)(Full text)