Late Pleistocene slip rate of the central Haiyuan fault constrained from optically stimulated luminescence, 14C, and cosmogenic isotope dating and high-resolution topography

The Haiyuan fault is a major left-lateral active fault of the India-Asia collision zone. While the 1000 km-long fault between Hala Lake in the west to Liupan Shan in the east accommodates eastward displacement of northeast Tibet relative to the Gobi-Alashan to the north, the amount of slip accumulated and its slip-rate remain debated. We revisit the site of Daqing (or Sangedun at 102.7°E in Gaudemer et al., 1995), to better constrain the long-term slip-rate of the Haiyuan fault in its central part. We used terrestrial LiDAR to build a high-resolution DEM and Unmanned Aerial Vehicle to build an aerial photomosaic with ~0.1 m resolution to survey the offset terraces, their geomorphology and the fault trace. We refine the geomorphological interpretation of the site, measure riser offsets and determine their relation to terrace formation. The well constrained age of the highest terrace T3 at 13.7 ± 1.5 ka determined from the combination of surface and sub-surface OSL, 14 C, and terrestrial in situ 10 Be cosmogenic nuclide dating, associated with the maximum lower terrace riser offset of 88 m yield a minimum slip-rate of 6.4±1.2 mm/yr over the late Pleistocene. The age of the intermediate terrace (T2) is bracketed between 8.0 ka (14 C) and 12 ka (10 Be). The ages and vertical offsets of the 2 highest terraces is used to infer the age of T2' offset vertically 5-7 m at 5.4±1 ka. Its 29±2 m offset is consistent with a rate of 6.5 mm/yr. Given the vertical offset youngest terrace T1 of 1.3±0.2 m its age is estimated at 1.2±0.2 ka in agreement with the youngest surface exposure age. Overall, a slip rate of 5-8 mm/yr fits all offset and age data at the Daqing site. The smallest offset of a gully incised into T1 of 6.0±0.5 m is potentially associated with the most recent slip event that occurred in the last millennia.