Differential surface uplift and knickpoint evolution along the transient Teesta river in the eastern Himalayas

Abstract

Tectonic and erosional processes that contribute to the gradual process of topographic uplift and erosion have shaped the Himalayan terrain. We used geomorphic proxies and previous published rates of erosion and exhumation across the Teesta River catchment to model the presence of transient segments. This helped us understand how the regional landscape has been changing over time due to surface uplift and channel incision. The Celerity model has been used to evaluate the knickpoint distribution and headward migration along the river system. Based on the river profile and Chi-(χ) analysis, the observed major knickpoints at about ∼ 2500–4000 m elevation comprise the fluvial erosion process, while higher elevation knickpoints suggest the glacial process. The strong significance of the model is shown by the observed correlation coefficient of 0.94 between the predicted and observed horizontal knickpoints. The analysis of relict reach for the paleo-channel reconstruction across the transient drainage channels shows a differential surface uplift of 3823 ± 252 m and 2372 ± 48 m with a corresponding relief gain. The rates of erosion and exhumation were spatially correlated with topographic metrics, precipitation intensity, knickpoint distribution, and surface uplift. The observation suggests that the rate of erosion tends to be more significant and spatially more varied than the long-term rate of exhumation. The rate of exhumation has been found to decline through topographic timescales from south to north, with rates as high as ∼ 1.0 mm/y in the southwest and as low as ∼ 0.4 mm/y in the northernmost Tessta catchment.