GLACIATION AND RELIEF PRODUCTION AT K2 IN THE KARAKORAM, HIMALAYA

The high Karakoram Himalaya has topography whose origin is currently not well understood, although the erosion/uplift feedback mechanism is now recognized to be a controlling factor. Numerous issues, including the role of surface processes, relief production, and estimating erosion, are complicated by the scale-dependencies associated with climate, tectonic and surface processes. Various topographic evolution models do not adequately account for polygenetic evolution and frequently assume river incision as the primary agent governing relief production. The K2 massif, in northern Pakistan, however, exhibits rapid exhumation rates, although the landscape is dominated by glaciation and mass movements. Consequently, we examined the landscape relief structure and topographic parameters of the massif to examine the linkages between surface processes and topography, and used imagery and digital elevation models to produce metrics as a proxy for erosion and denudation.

Hypsometric analysis reveals that the majority of the landscape (74 %) occurs between 3000-5000 m, with a mean elevation of 5,140 m. The K2 hypsometric curve is similar in shape to Nanga Parbat's, although the hypsometric integral is higher at 0.44 compared to the 0.38 of Nanga Parbat. Swath profile analysis indicates that directional regional relief is highly variable, and in the west-east direction, relief is greater south of K2, compared to the north. Analysis of scale dependency reveals that in the absence of local high-discharge rivers, variation in relief is dramatically reduced as compared to Nanga Parbat. The slope-altitude function is non-linear, and relatively low slope angles at high altitudes document erosion by glaciers up to ~6000 m. Our preliminary analyses suggest that glaciation is primarily responsible for the relief production at K2, and given the relief structure of the landscape, the denudation/uplift mechanism is likely governed by climate forcing. These findings indicate that landscape-evolution models need to account for the coupling of glaciation with other processes to account for the polygenetic evolution of high-mountains.