Gravimetric Constraints on the Rheology of the Indian and Tarim Plates in the Karakoram Continent-Continent Collision Zone

Bouguer gravity anomalies in the region of the Western Himalayas, Karakoram and Tien Shan show large negative values, but classical isostatic models are insufficient to account for the detailed pattern of the observed anomalies. In the past years gravimetric surveys in the Karakoram (Marussi, Caputo and others in 1954) have been extended and densified. The full body of available gravimetric data, including the pendulum observations by De Filippi in 1913-14 and Hedin in 1929-33 have been re-analyzed. Terrain corrections have been computed systematically for all available data using an algorithm and Digital Terrain Model. The isostatic anomalies along a profile from the Indo-Gangetic foredeep, across the Karakoram Range and terminating in the Tarim Basin show the oscillating values already noticed by Marussi. This oscillatory pattern can be explained by a model in which the convergent boundaries of the Indian and Tarim plates deform by elastic flexure, besides isostacy. The gravity data ...