Abstract
The lakes at the southern Mongolian Plateau are sensitive to the variation of EASM changes during the Holocene, and hence the lacustrine records of these lakes provide prospects for understanding how lake environmental changes respond to EASM variation at different timescales. The interpretation of proxy indexes of lacustrine sediments is complex due to the various climatic or/and environmental factors influencing the processes during deposition and after deposition. In this study, the elements and colors of an 11.7-m lacustrine record from Chagan Nur at the southern Mongolian Plateau of northern China were analyzed to constrain the lake environmental changes during the Holocene. The results show that stable elements of Al, Si, K, Ti, Fe, and Rb are more related to surface erosion or/and vegetation coverage, and the variation of Sr is related to the lake-level change in Chagan Nur. The element and color of the lacustrine records show that a small and shallow lake environment occurred at Chagan Nur during 11.7–10.5 ka, the lake level had increased during 10.5–7 ka, and then the lake shrank with strength surface erosion during 7–6.2 ka and from 2 ka to the present. The lake level and surface erosion changes of Chagan Nur have shown a direct response to EASM precipitation changes as reconstructed from the pollen record from the Chagan Nur Lake and other records from northern China.
Highlights
East Asian summer monsoon (EASM) is the crucial atmospheric circulation system for East Asia, for it provided amounts of fresh water to all of the lives (An et al, 2015; Chen et al, 2015; Chen et al, 2020)
The results suggested that the variation of EASM dominated the paleoenvironmental changes in Chagan Nur basin at the margin of EASM dominance, which influenced the lake level and influenced the vegetation coverage and surface erosion
Based on the chronology obtained by the radiocarbon and luminescence dating, in combination with the results of elements, color from an 11.7 m Chagan Nur lacustrine core, we have reconstructed variations of the surface erosion and lake level on the fringe of modern EASM dominance in northern China during the Holocene
Summary
East Asian summer monsoon (EASM) is the crucial atmospheric circulation system for East Asia, for it provided amounts of fresh water to all of the lives (An et al, 2015; Chen et al, 2015; Chen et al, 2020). The southern Mongolian Plateau located at the margin of EASM is an ideal place to study the mechanism and variation of EASM. Chagan Nur Lake locates at the southern Mongolian Plateau, which is exactly located at the fringe of the modern EASM. Jiang et al (2016) and Han and Liu (2017) have reported that the paleoclimatic variations were affected by the changes of summer insolation using the proxies of grain size and pollen from west Chagan Nur over the past 2 ka and 7 ka, respectively. Liu and Ha (2015) has reconstructed the lake level since the past 6.8 ka by using paleolake shoreline records, and it showed that the paleolake level was at least 7 m higher than the present and gradually shrank till now. Jiang et al (2016) and Han and Liu (2017) have reported that the paleoclimatic variations were affected by the changes of summer insolation using the proxies of grain size and pollen from west Chagan Nur over the past 2 ka and 7 ka, respectively. Liu and Ha (2015) has reconstructed the lake level since the past 6.8 ka by using paleolake shoreline records, and it showed that the paleolake level was at least 7 m higher than the present and gradually shrank till now. Chun et al (2017) and Chun et al (2018) has reported the variations of precipitation, temperature, and population in recent 50 years and further pointed out their effects on the changes of the lake level and vegetation coverage, and the results suggested that the variation of precipitation was the most fundamental factor for the recovery of vegetation and the rise of the lake level
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