Dust Storm Recorded By Lake Genggahai Since 15 Ka BP

The Gonghe Basin is situated at the northeastern margin of the Qinghai-Tibetan Plateau. In the area, the surface winds is stronger, especially in winter and spring, due to the prevailing cold surge at that time. The Gonghe Basin is separated by a series of low mountains naked by drying processes from the Qaidam Basin, the two arid basins could be recognized as the main dust source area in the northeastern Qinghai-Tibetan Plateau. A hydrologically closed lake, Lake Genggahai with a relatively simple hydrological precess, is located in the Gonghe Basin and can be employed to reconstruct history for dust storm since the late glacial in this area.AMS 14C dating is based on the plant remains and seeds preserved in the core sediments. After deduction of the reservior effect (1010 years) and calibration to calendar ages, the chronological sequence was established. The results indicate that the GGHA cores cover the whole Holocene and the last Deglaciation. Based on grain size, clastic material flux,δ13Corg, TOC, TON, C/N, carbonate content, and abundance ratio of plant remains and carbonate encrustation of submerged plant, the dust storm history is reconstructed over the past 15 300 cal a.There are five strong dust storm periods, i.e.,10 800-10 350,6 100-5 400,4 700-3 100,1 900-1 550 and 250-0 cal a BP. Generally speaking, dust storms always occurred during time when lake level is low relatively. This is consistent with other records from the adjacent regions. However, some events still took place during wetter periods, characterized with a higher lake level. For instance, the dust storms were intensive and/or frequent between 6 100 and 5 400 cal a BP, while the lake level is higher during the late period of this event. It is suggested that dust storm may not entirely response to environment drying.The strongest dust storm event from 6 100 to 5 400 cal a BP is also reflected by the high terrestrial dust flux in the pelagic sediments of north Pacific Ocean and the Greenland ice core. Cooling in the higher latitudes, e.g., the northern Atlantic, may strengthen the Mongolia-Siberian High during the mid-Holocene. Outbreaks of the High in spring, combining with the shift of high-level Westerlies, could cause intensive dust storms across arid northern China. Under this condition, dust can be entrained into the air and be transported to the distal regions, e.g., the north Pacific and the Greenland ice sheet. This process perhaps explains the relationship between the Asian dust source areas and remote dust depositional areas during the mid-Holocene. In addition, the Gonghe Basin, even the arid regions of northwestern China, should be one of source areas of Asian dust, which can be transported for a long-range.