Late Holocene mobilisation of loess-like sediments in Hohuan Shan, high mountains of Taiwan

Silty cover soils are found in lower slope positions in the highest massifs of the high mountains of Taiwan. They are not formed under present-day conditions, and remain well preserved in locations not affected by fluvial morphodynamics. This study focuses on an outcrop in the Hohuan Mountain summit area. The sediment infill of a gully is described, and sediment properties are analysed. Size-frequency distributions of the sediment grains suggest that they are partly aeolian deposits. The loess-like sediments yielded OSL ages between 3.65 ± 0.62 ka and 1.72 ± 0.48 ka. Results from radiocarbon dating of organic-rich bulk sediments support the age estimates from OSL. The timing of gully infilling coincides with a cool and dry phase reported by palynological studies from Toushe Basin and Chitsai Lake. The sediment record reflects a large-scale climatic change to cooler and less humid conditions in the Hohuan Mountain area.