Landscape evolution of the Eastern Himalayan Syntaxis based on basin hypsometry and modern crustal deformation

Abstract

Basin hypsometry is sensitive to tectonic uplift and erosion. An area of intense tectonism, the Eastern Himalayan Syntaxis (EHS) is used to explore the characteristics of basin hypsometry and discuss the dominant variables controlling landscape evolution. We selected 137 primary drainage basins and delimited their subordinate basins according to Strahler order. The hypsometric integrals and corresponding hypsometric curves of catchments are spatially independent of lithologic factors and basin scales but correlate strongly with indices of vertical dimension of drainage basins (i.e. mean altitude and maximum altitude). These observations also suggest different relationships between tectonic uplift and surface erosion around the Namche Barwa syntaxis (NBS). The area northwest of the NBS, the NBS itself, and the Chayu deformation belt are in stages of sinking, approximate steady state, and rising, respectively. Combined with GPS data and the regional earthquake distribution, we suggest that the present tectonic uplift of the EHS is concentrated in the NBS and the Chayu deformation belt to the southeast of the NBS; while the actual uplift of the earth's surface and significant horizontal crustal shortening is only concentrated within the Chayu deformation belt. The center of crustal deformation of the EHS therefore is inferred to have migrated southeastward from the NBS to the Chayu deformation belt.