HOLOCENE SHORTENING RATE ACROSS THE EASTERN HIMALAYAN FRONT AND IMPLICATIONS FOR GROWTH MECHANISMS OF THE HIMALAYA

How plate-boundary processes control the growth of the Himalaya is unclear. To address this issue, we investigated the Main Frontal Thrust (MFT) zone across the eastern Himalayan front. Using the ages and geometry of uplifted river terraces, we establish a minimum Holocene slip rate of 23.7 +/- 6.2 mm/yr along the MFT decollement. This slip rate is partitioned on three structures: at ~8.4 mm/yr on the Bhalukpong thrust in the north, at ~10 mm/yr across the growing Balipara anticline in the middle, and at ~5 mm/yr on the Nameri thrust in the south. Our estimated minimum total shortening rate is significantly higher than the Holocene slip rate of 9.7 +/- 3.0 mm/yr on the MFT in the western Himalaya but similar to or potentially greater than the slip rate of 21.7 +/- 1.5 mm/yr for the MFT in the central Himalaya. The eastward increase in the Holocene MFT slip rate requires that the plate-boundary force rather than gravitational spreading is the fundamental control on active growth of the Himalayan orogen.