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The Xiaohe Cemetery archaeological site (Cal. 4-3.5 ka BP) is one of the most important Bronze Age sites in Xinjiang, China. Although the surrounding environment is an extremely arid desert now, abundant archaeological remains indicate that human occupation was common during certain periods in the Holocene. Field investigations and laboratory analyses of a sediment profile near the Xiaohe Cemetery indicate that while the regional environment was arid desert throughout the Holocene there were three episodes of lake formation near the site in the periods 4.8-3.5 ka BP, 2.6-2.1 ka BP and 1.2-0.9 ka BP. Geomorphic and hydrological investigations reveal that a lake or lakes formed in a low-lying area when water was derived initially from the Kongque River and then shunted into the Xiaohe River basin. Low amounts of active chemical elements in lacustrine sediment between 4.8-3.5 ka BP indicate abundant and continuous water volume in the lake; the content of active chemical elements increased between 2.6-2.1 ka BP but was still at a relatively low level, suggesting a declining amount of water and diminished inflow. Between 1.2-0.9 ka BP there was a very high content of active elements, suggesting decreased water volume and indicating that the lake was stagnate. In contrast, the general climate condition shows that there had a warm-humid stage at 8-6 ka BP, a cool-humid stage at 6-2.9 ka BP and a warm-dry stage at 2.9-0.9 ka BP in this region. The hydrological evolutions around Xiaohe Cemetery did not have one-to-one correspondence with climate changes. Regional comparison indicates that broad-scale climatic conditions played an important role through its influences on the water volume of the Tarim River and Kongque River. But, the formation of the lakes and their level were controlled by geomorphic conditions that influenced how much water volume could be ZHANG Yifei et al.: Holocene environmental changes around Xiaohe Cemetery and its effects on human occupation 753 shunted to Xiaohe River from Kongque River. Human occupation of the Xiaohe Cemetery and nearby regions during the Bronze Age and Han-Jin period (202 BC-420 AD) corresponded to the two earlier lake periods, while no human activities existed in the third lake period because of the decreased water volume.

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Prehistoric land use at the Guobei site and its relationship with the local 15 environment are examined by applying OSL dating, micromorphological 16 examination and geo-physical analysis. The majority of the OSL dates are of early 17 to middle Holocene ages and are thus comparable to many OSL dates derived 18 from other studies in the same region. According to the particle size analysis, silt-19 sized particles (2-60μm) were predominant throughout the profiles examined. 20 However, there are spatial and temporal variations of different size groups of 21 particles throughout the profiles, which provide complementary information for 22 the micromorphological interpretation. The total organic component of the 23 samples examined through LOI is relatively high (all > 2%), with those of the 24 overlying Holocene deposits higher than those of the underlying Malan loess by 25 about 0.2%. Moreover, in all three profiles, the highest organic contents appear 26 in the palaeosols, confirming that there was greater organic accumulation during 27 soil formation periods. The groundmass of most slides collected from the early to 28 middle Holocene horizons displays a very homogeneous pattern, while the 29 abundance and distribution of different kinds of pedo-features, mainly including 30 clay textural, calcitic, iron/Mn and crustal features, vary greatly temporally and 31 spatially. These different lines of information demonstrate diversified 32 pedo/sedimentary processes due to variations in micro-environmental 33 conditions and cultural activities. We discuss the importance of a palaeo-34 ecological perspective, allowed by the geoarchaeological study, to an improved 35 understanding of the relationship between loess, changing hydrology, 36 prehistoric farming practice and land use, and long-term landscape change in the 37 Chinese Loess area. This will thus contribute to a comparison on the dynamic 38 relationship between loess and prehistoric farming in other regions of the world 39 such as Europe and North America. 40 2 41