XiangJun Liu

Luminescence Chronology and Radiocarbon Reservoir Age Determination of Lacustrine Sediments from the Heihai Lake, NE Qinghai-Tibetan Plateau and Its Paleoclimate Implications

The accurately determining the lake 14C reservoir age has a crucial significance for climatic reconstruction. In this study, the optically stimulated luminescence (OSL) dating method is employed to date samples from highstand lacustrine sediments, palaeoshoreline, fluvial terrace, and the alluvial fan of the Heihai Lake catchment. Accelerator mass spectrometry (AMS) 14C dating was also used to date fossil plants from highstand lacustrine sediments. Based on the calculations of linear regression with OSL against radiocarbon ages for same layers of two sections, the quantitative 14C reservoir ages were estimated to lie between 3 353 and 3 464 yr during the 1.8 to 2.4 ka, which showed temporal variation. The sources of old carbon are the dissolution of carbonate bedrocks distributed along the Kunlun Mountain. The OSL ages of the different members of the hydatogen sedimentary system at Heihai Lake catchment indicate that a stronger hydrologic condition occurred from 3.0±0.2 to 1.8±0.2 ka, with a maximum lake level of 9 m higher than present. This humid stage was widely recorded in different sediments on the QTP and Chinese Loess Plateau (CLP), indicating its broad synchronicity across the Asian Summer Monsoon region. The enhanced East Asian Summer Monsoon (EASM) and the Indian Summer Monsoon (ISM) resulted in the increase of moisture availability for the Heihai Lake area during this stage.

Long-term east-west asymmetry in monsoon rainfall on the Tibetan Plateau Comment

[Hudson and Quade (2013)][1] suggest that an early Holocene increase in the size of lakes on the Tibetan Plateau ([Fig. 1A][2]) was caused by increased precipitation. They used the area within high paleoshorelines to reconstruct paleorainfall patterns, and found that paleolake area increased

A comparative study of radiocarbon dating on terrestrial organisms and fish from Qinghai Lake in the northeastern Tibetan Plateau, China

Qinghai Lake is the largest lake on the Tibetan Plateau (TP) and in China and has been a focus of paleoenvironmental and climatic research for decades. However, limited understanding of lake 14C reservoir effects (LRE) has led to inconsistent interpretations among proxies of different sediment cores. As such, the onset of LRE variability during the Holocene is still unclear. 14C dating of archeological samples from four locations (Gangcha, Shaliuheqiaoxi, and Shinaihai sites, and Niaodao section) including naked carp (Gymnocypris przewalskii, Kessler) fish bones, animal bones and teeth, and charcoal was employed to estimate variations in LRE over the last few thousand years. LRE offsets calculated as the difference between LRE of animal bones and fish bones are more reliable than that of charcoal and fish bones due to the ‘old wood’ effect in charcoal. LRE offsets recorded in fish bones were ~0.5, ~0.6, and ~0.7 ka during the periods of 3.0–3.4 cal ka BP, 0.58–0.60 cal ka BP, and modern lake times, respectively, which may indicate a temporal minimum LRE offset. Unlike the wide spatial variations of LRE ages obtained from surface total organic carbon (TOC) samples of the modern Qinghai Lake, LRE offsets from the three contemporaneous locations in Qinghai Lake were all ~0.5 ka, suggesting efficient carbon mixing occurred in naked carp. However, the late-Holocene (~3.1 ka BP) LRE increased slightly with increasing salinity and decreasing lake level.

Land Cover Changes in Qaidam Area from 2000 to 2008

Qaidam Basin is one of the largest arid regions in the middle latitude Asia, which is surrounded by high mountains. The ecosystem of this region is fragile due to limited annual precipitation amounts in the interior basin and large temperature differentia between winter and summer on the surrounding mountains. Several researchers have reported vegetation cover in this area had degraded in the past several decades with the climate changes and human activity. In this study, we use 1-km resolution moderate-resolution imaging spectroradiometer (MODIS) normalized difference vegetation index (NDVI) to explore land cover changes in Qaidam area from 2000 to 2008 based on combine decision tree (DT) and spectral angle (SA) classification methods. An accuracy test illustrates the classification are of credible accuracy for both time periods. Analysis results indicate that vegetation cover has increased for the past 9 years in the Qaidam Area, and lake areas and multi-year snow/ice cover areas have also increased significantly, while barrenland has decreased.