Glacial and fluvial erosion in the Dolpo Basin, Western Nepal

The landscape of Western Nepal has been dramatically shaped by tectonics and by both glacial and fluvial erosion. Here we investigate the modern geomorphic and glacial features of the Dolpo basin in northern mid-western Nepal. We analyze attributes such as glacier size, slope, aspect and toe, head and peak elevation for 446 glaciers within and around the basin, determining their relationship with basin features such as lithology, slope and precipitation. Glaciers reflect lithology and precipitation, but glacier size is strongly correlated with base-level and slope. Our data suggest that low-slope glaciers with high base-level, i.e., those that flow onto the Tibetan plateau, are forced to grow large because they exist at or above the equilibrium-line altitude. Glaciers within the basin, particularly in the western part, can become dismembered on steep slopes, an effect only partly offset by precipitation. The spatial variability in regional slope and presence of a wind gap along the northern basin border suggest recent capture of the Dolpo basin. A plateau-like morphology would have thus once extended at least 45 km southward. The southward opening of the basin allowed precipitation to enter, forming glaciers along the western end of the northern basin border. Larger glaciers (resulting from high base-level) pushed the ridge southward over time through headward erosion. Our study suggests dramatic landscape reorganization in western Nepal, consistent with other recent studies suggesting a more extensive proto-Tibet.