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The Shiyang River drainage basin is located in the northwest margin of the Asian monsoon region. Previous studies reached different conclusions about Holocene climatic changes in the basin. Some studies suggested the Holocene climatic changes were mainly controlled by the Asian monsoon and that the climate was relatively humid during the early Holocene (11.6--7.1 cal ka BP). Other studies found the mid-Holocene Climatic Optimum (7.0--5.0 cal ka BP), and this climate condition was similar to the Holocene westerly wind pattern in arid Central Asia. The modern climate is affected by the Asian monsoon and westerly wind in the drainage basin, and the Holocene climatic records showed two different Holocene climatic patterns--a westerly wind pattern and monsoonal pattern. However, it remains unclear what caused the two different Holocene climatic patterns to co-exist in the region. The palynological records are the main evidence for the Holocene climatic changes in the basin. This paper focuses on palynological records for different parts of the drainage basin. Among them, QTH02, QTL-03 and Sanjiaocheng records are located in the terminal lake, and the Hongshuihe record is located in the middle reaches of the basin. In the terminal lake, the palynological records of QTH02 and QTL-03 are similar, but the Sanjiaocheng record differs. The difference is mainly affected by the variable pollen assemblages in the different locations of the lake basin. From comparison and synthesis of the four palynological records, we concluded that the millennial-scale Holocene climatic changes were affected by the combined effects of the Asian monsoon and westerly wind in the drainage basin, which show the complicated Holocene climatic pattern in the northwest margin of the Asian monsoon. [ABSTRACT FROM AUTHOR]

A Holocene palaeorecord from Lake Shudu, Yunnan Province, southwestern China is dominated by (1) a pronounced basin-wide sedimentary hiatus after ca. 7.2 kcal yr BP, spanning some 4,000 years and (2) significant changes in sediment source/supply and an increase in heavy metal influx coupled with a shift to more eutrophic lake conditions from ca. 0.9 kcal yr BP, lasting ~300 years. The hiatus is most likely a due to a significant and abrupt reduction in sedimentation rates, the driver of which is unclear; although it appears likely to have been climatically driven. The environmental changes captured in the Lake Shudu palaeorecord provide unambiguous evidence of late Holocene anthropogenic activity, most likely linked to mining activity. [ABSTRACT FROM AUTHOR]