HOLOCENE LEFT-SLIP RATE DETERMINED BY COSMOGENIC SURFACE DATING ON THE XIDATAN SEGMENT OF THE KUNLUN FAULT (QINGHAI, CHINA)

Cosmogenic dating, using in situ Al-26 and Be-10 in quartz pebbles fro m alluvial terrace surfaces, constrains the late Holocene slip rate on the Xidatan segment of the Kunlun fault in northeastern Tibet. Two te rrace risers offset by 24 +/- 3 and 33 +/- 4 m, having respective ages of 1788 +/- 388 and 2914 +/- 471 yr, imply a slip rate of 12.1 +/- 2. 6 mm/yr. The full range of ages obtained (less than or equal to 22.8 k .y., most of them between 6.7 and 1.4 k.y) confinn that terrace deposi tion and incision, hence landform evolution, are modulated by post-gla cial climate change. Coupled with minimum offsets of 9-12 m, this slip rate implies that great earthquakes (M similar to 8) with a recurrenc e time of 800-1000 yr, rupture the Kunlun fault near 94 degrees E.