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Abstract: Determining the slip-rate history along the right-lateral Karakorum fault (KF) is fundamental to understanding its present-day kinematic role in the deformation of Tibet. Geodetic and geologic studies suggest slip-rates of 0–11mm/yr along this structure. Whether slip-rate variability exists along strike and/or time, or simply results from different measuring techniques/timescales, remains unknown. In order to constrain slip-rates within a timescale of 200ka, we studied fluvial and glacial geomorphic features that are right-laterally or vertically offset by the fault by varying amounts from 7±1m to 430±30m and up to 53±5m, respectively. We constrained their ages using 10Be surface exposure dating on 141 quartz-rich samples collected on 4 lateral moraines and at 3 alluvial sites along the southernmost segment of the KF (Menshi–Kailas basin) and along the Gurla Mandhata detachment fault in the Pulan graben. From the 30° fault bend at Baer (80.5°E) to Mount Kailas area, the slip-rate along the KF is >7.1+3.2/−1.7 mm/yr at Menshi and >7.9+3.2/−2.5 mm/yr at Kailas (slip on two parallel fault strands). In the Pulan graben, the normal fault slip-rate is >1.6+0.4/−0.3 mm/yr. Our data suggest that the Quaternary slip-rate along the southern KF does not decrease eastward but is constant along strike for at least 200km, from >5–11mm/yr in the Gar basin further north to >7–8mm/yr in the Menshi–Kailas basin. Because no expected along-strike slip-rate gradient is observed, it implies that the KF does not end at the Kailas but must extend where the slip rate decreases, i.e. eastward along the Yarlung Zangbo suture and southward along the Gurla Mandhata–Humla fault system. [Copyright &y& Elsevier]

Structural style along the active, NW-striking, right-slip Karakoram fault in western Tibet ranges from transpression in the north (37° to 34°N) to transtension in the south (34° to 32°N). This transition in structural style occurs at a 27-km-wide bend in the fault. Our new neotectonic mapping has documented the long-asserted structural linkage between the ENE-striking Gozha–Longmu Co fault system and the similarly oriented active, leftslip Altyn Tagh fault to the northeast. This mapping also indicated that the restraining bend in the Karakoram fault is located where this fault intersects the Gozha-Longmu Co extension of the Altyn Tagh fault to the west. Additional observations from remotely sensed imagery suggest that the total left-separation along the Gozha-Longmu Co fault system is 25-32 km. We use the new neotectonic mapping and published slip rates to develop a simple kinematic model for the main active faults in western Tibet to explore the genetic relationship between slip along the Gozha- Longmu Co fault system and the geometric and kinematic evolution of the Karakoram fault. This model combines published geodetic and Quaternary slip rates with the known fault geometries and demonstrates that the transition from transpression to transtension along the Karakoram fault can be explained by differential motions between the NW Himalaya, the Tianshuihai terrane, and the Tibetan Plateau. These motions produce bending and transtension along the central and southern Karakoram, respectively, and movement of the Tibetan Plateau at a rate of 6–13 mm/ yr toward the east-southeast relative to the Pamirs. We also fi nd that the Gozha–Longmu Co fault system likely initiated between 10 and 3 Ma to accumulate 25–32 km of total left separation. We suggest that the Gozha-Longmu Co fault system formed during late Miocene to Pliocene structural reorganization of the southwestern Altyn Tagh and southern Karakoram fault systems to allow eastward migration of the Tibetan Plateau and northward migration of the Pamir syntaxis. [ABSTRACT FROM AUTHOR]