High‐resolution records of climate change in arid eastern central Asia during MIS 3 (51 600–25 300 cal a BP) from Wulungu Lake, north‐western China

Zhang, Xiaonan; Zhou, Aifeng; Zhang, Can; Hao, Shengtun; Zhao, Yongtao; An, Chengbang

doi:10.1002/jqs.2881

Cited by 20 publications

(7 citation statements)

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“…As indicated by the lithologies corresponding to these endmembers, CEM 1 is represented in brown silty clay and CEM 2 in gray silty clay. According to the results of a previous study (Zhang et al, 2016), gray silty clay contains relatively high feldspar (17%) and low illite (35%), whereas brown silty clay has a high concentration of illite (47%) and a low concentration of feldspar (11%). Illite-rich sediments have been interpreted as representing relatively dry conditions (Singer, 1984).…”

Section: Discussionmentioning

confidence: 85%

“…Wulungu Lake is a hydrologically closed terminal lake fed mainly by the Wulungu River. The sediments studied are from a 7-m-long core (WLG11E) taken from the central part of the lake (47°14.40′N, 87°13.10′E) in a water depth of 18 m. The sediments studied here accumulated during Marine Oxygen Isotope Stage 3, between ~25,300 and 51,600 cal yr BP (Zhang et al, 2016). The core is mainly composed of silty clay with occasional thin intercalated layers of silt or gypsum.…”

Section: A Case Study: the Sediments Of Wulungu Lake Junggar Basin mentioning

confidence: 99%

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Unmixing grain-size distributions in lake sediments: a new method of endmember modeling using hierarchical clustering

et al. 2017

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The grain-size distribution (GSD) of sediments provides information on sediment provenance, transport processes, and the sedimentary environment. Although a wide range of statistical parameters have been applied to summarize GSDs, most are directed at only parts of the distribution, which limits the amount of environmental information that can be retrieved. Endmember modeling provides a flexible method for unmixing GSDs; however, the calculation of the exact number of endmembers and geologically meaningful endmember spectra remain unresolved using existing modeling methods. Here we present the methodology hierarchical clustering endmember modeling analysis (CEMMA) for unmixing the GSDs of sediments. Within the CEMMA framework, the number of endmembers can be inferred from agglomeration coefficients, and the grain-size spectra of endmembers are defined on the basis of the average distance between the samples in the clusters. After objectively defining grain-size endmembers, we use a least squares algorithm to calculate the fractions of each GSD endmember that contributes to individual samples. To test the CEMMA method, we use a grain-size data set from a sediment core from Wulungu Lake in the Junggar Basin in China, and find that application of the CEMMA methodology yields geologically and mathematically meaningful results. We conclude that CEMMA is a rapid and flexible approach for analyzing the GSDs of sediments.

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Section: Discussionmentioning

confidence: 85%

Section: A Case Study: the Sediments Of Wulungu Lake Junggar Basin mentioning

confidence: 99%

Unmixing grain-size distributions in lake sediments: a new method of endmember modeling using hierarchical clustering

et al. 2017

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“…The number of endmembers, as well as the endmember spectra and fractions, can be inferred sequentially when the posterior probability distributions converged. These endmembers are interpreted as representing sediment transport processes and thus are characteristic of specific depositional environments (Zhang et al, 2016).…”

Section: Methodsmentioning

confidence: 99%

Sedimentary grain-size record of Holocene runoff fluctuations in the Lake Lugu watershed, SE Tibetan Plateau

Zhang

Chang

et al. 2020

The Holocene

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Changes in moisture conditions or precipitation in the SE Tibetan Plateau during the Holocene have been studied using various environmental archives and proxies. However, due to different interpretations of the proxies and records, the pattern of Holocene precipitation/moisture variations in the region remains unclear. A lake-sediment-based reconstruction of runoff variations, which can directly and sensitively reflect changes in precipitation, provides the opportunity to reconstruct the evolution of moisture conditions in the SE Tibetan Plateau during the Holocene. In this study, we used a well-dated sediment core (LGH2) from Lake Lugu, a deep alpine lake charged mainly by precipitation on the lake surface and by runoff from the watershed, to reconstruct variations in runoff during the Holocene. In addition, 70 lake surface sediment samples were collected to examine the spatial variation of grain size. Endmember modeling analysis of the grain-size data was used to characterize the processes of sediment transport and runoff fluctuations. The carbonate content of core LGH2 shows that the lake level was generally high during 11,600–3100 cal years BP, and that the lake basin was closed after 3100 cal years BP and semi-closed since 90 cal years BP. Grain-size endmember EM 3, which represents the runoff input clastic materials, is used to reconstruct runoff fluctuations in the Lake Lugu watershed. The record indicates a gradual increase in runoff during 11,600–9000 cal years BP, stable and high runoff during 9000–2000 cal years BP, and weak runoff and a low lake level since 2000 cal years BP. Our reconstruction of runoff fluctuations tracks changes in regional temperature and tropical SSTs rather than in boreal summer insolation. This finding supports the hypothesis that increasing tropical SSTs strengthened ITCZ convection which enhanced the flux of water vapour from the ocean to the air, and hence the moisture supplies to SW China.

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“…Within the framework of BEMMA, the number of EMs as well as the EM spectra and fractions can be inferred sequentially using a reversible-jump Markov Chain Monte Carlo algorithm in conjunction with Gibbs samplers. These EMs are believed to represent the sediment transport processes and thus are characteristic of typical depositional environments (Yu et al, 2016a; Zhang et al, 2016).…”

Section: Methodsmentioning

confidence: 99%

Moisture evolution in North Xinjiang (northwest China) during the last 8000 years linked to the westerlies’ winter half-year precipitation

et al. 2020

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Winter half-year precipitation dominates variations in hydroclimatic conditions in North Xinjiang, but few researchers have focused on this very important aspect of the Holocene climate. Here we report multiproxy evidence of Holocene hydroclimate changes from the sediments of Wulungu Lake in North Xinjiang. The site is a closed terminal lake fed mainly by meltwater from snow and ice, and today the area is climatically dominated by the westerlies. Grain-size end-member analysis implies an important mode of variation that indicates a gradually increasing moisture trend, with superimposed centennial-scale variations, since 8000 cal yr BP. From 8000 to 5350 cal yr BP, a permanent lake developed, and the lake level gradually rose. Between 5350 and 500 cal yr BP, the moisture status increased rapidly, with the wettest climate occurring between 3200 and 500 cal yr BP. After 500 cal yr BP, the lake level fell. The trend of increasing Holocene wetness indicates a rising winter precipitation in North Xinjiang during the Holocene. This was due to an increase in upwind vapor concentrations caused by increased evaporation and strength of the westerlies, which were determined by the increasing boreal winter insolation and its latitudinal gradient.

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High‐resolution records of climate change in arid eastern central Asia during MIS 3 (51 600–25 300 cal a BP) from Wulungu Lake, north‐western China

Cited by 20 publications

References 50 publications

Unmixing grain-size distributions in lake sediments: a new method of endmember modeling using hierarchical clustering

Unmixing grain-size distributions in lake sediments: a new method of endmember modeling using hierarchical clustering

Sedimentary grain-size record of Holocene runoff fluctuations in the Lake Lugu watershed, SE Tibetan Plateau

Moisture evolution in North Xinjiang (northwest China) during the last 8000 years linked to the westerlies’ winter half-year precipitation

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