Publication Date:
2015-02-03
Description:
This study investigates the first-order Himalayan mountain topography from the perspective of deep-crustal flow patterns in the Indo-Asia collision zone. Using a thin-viscous-sheet model we theoretically predict that flat hinterland topography with a stable elevation (Type I) can develop only when the lithospheric slab underthrusts with a threshold velocity ( V s * ). For V s 〉 V s * , the hinterland continuously gains in elevation, leading to Type II topography. This type is characterized by varying first-order surface slopes, but always facing the mountain front. Conversely, the elevated hinterland masses undergo gravity-driven subsidence, forming a topography (Type III) with characteristic backward surface slopes when V s 〈 V s * . We evaluate V s * as a function of: (i) the regional slope of the initial first-order surface topography (α); (ii) the angle of underthrusting (β); and (iii) the relative width of foreland plain (), assuming little effects of surface erosion. Our model shows two characteristic deep-crustal flow patterns: corner flow and vortex flow. The corner flow pattern, described by upwardly pointed hyperbolic streamlines, is responsible for Type II topography. Conversely, the vortex flow leads to Type III, whereas the transition between the two gives rise to Type I. This corner-to-vortex type flow transition commences on decreasing V s .
Print ISSN:
0305-8719
Electronic ISSN:
2041-4927
Topics:
Geosciences
