The origin and sources of loess-like sediment in the Jinsha River Valley, SW China

The grain size of the loess-like sediment in the Jinsha River Valley is essentially similar to that of typical loess, and it differs from that of the fluvial sediment in the Jinsha River area. We conclude that the loess-like sediment is of aeolian origin, as is the loess of the Chinese Loess Plateau. The geochemical characteristics of the loess-like sediment are similar to those of dammed lake and fluvial sediments in the same area, which is significantly different from those of the typical loess in NW China. The geochemical characteristics show that the loess-like sediment originated from proximal materials. Combined with the grain-size distribution pattern of the aeolian deposits, we suggest that the loess-like sediment of the Jinsha River Valley originated from the dammed lake and fluvial sediments that accumulated in the valley. The local mountain-valley wind circulation (especially the valley wind in winter and spring) provided the transport force for the loess-like sediment. The presentation of the loess-like sediment may indicate the appearance of the grassland and forest steppe and the beginning of the dry-hot valley phenomenon.