Abstract
An excavated profile of aeolian-palaeosol-lacustrine sediments (the Wapianliang profile), located at the southeastern part of the Mu Us Desert, Northern China, was studied to reconstruct regional Holocene environmental changes. A chronology was established based on three AMS 14C and two OSL dates, and variations in the lithology and grain size, magnetic susceptibility, soil micromorphology, and chemical elements were used to explore the regional depositional environments during the Holocene. The results showed that since around 14 ka BP, this region had experienced seven alternations of wetting and drying. A shallow lake, which was identified by celadon lacustrine sediments with sporadic freshwater gastropod fossils, occurred in this area from around 13.0 ka BP to 9.9 ka BP. There existed two obvious intervals of soil formation, inferred from the environmental proxies of the palaeosol/sandy palaeosol layers, with relatively fine average grain-size, high magnetic susceptibility value, remarkable pedogenesis features, and strong chemical weathering, in particular, a well-developed palaeosol layer dating from the middle Holocene (8.6 ka BP to 4.2 ka BP). A weakly-developed palaeosol layer (from around 1.2 ka BP) at the upper part of the profile is possibly an indication of the Medieval Warm Period. This implies a forest steppe environment at both of these sedimentary stages. After 0.9 ka BP, a desert environment returned, analogous to before around 13.0 ± 1.4 ka BP, between 9.9 ± 1.1 ka BP to 8.6 ka BP, and between 4.2 ka BP to 1.6 ka BP, indicating the aggravation of aeolian activity and the expansion of mobile sand dunes. The variations in sedimentary environments were mainly triggered by changes in the East Asian Summer Monsoon (EASM).
Highlights
The Holocene may appear as a blink of an eye considering the long history of the Earth, yet it is vitally important to understanding current and recent environmental conditions (Qin, 2011)
The Mu Us Desert in Northern China is located in a desertloess transitional zone, on the northern margin of the East Asian Summer Monsoon (EASM), within a farming-grazing transitional belt (Figure 1)
Since the 1920s, efforts to understand Holocene palaeoclimate in the Mu Us Desert have found that under the background of climatic variation during the Holocene, aeolian and fluvio-lacustrine deposits coexisted, and the differences that arose concerned the proportion of these different lithologies over time (Liu et al, 2018a), which has been confirmed by various geological records (Ding et al, 2021; Shu et al, 2021)
Summary
The Holocene (from around 11.7 ka BP to the present) may appear as a blink of an eye considering the long history of the Earth, yet it is vitally important to understanding current and recent environmental conditions (Qin, 2011). The frequent variations in lacustrine and aeolian activities recorded in individual profiles indicate the quick response and feedback of the regional climatic and environmental changes (Li et al, 2012; Liu et al, 2018a). Since the 1920s, efforts to understand Holocene palaeoclimate in the Mu Us Desert have found that under the background of climatic variation during the Holocene, aeolian and fluvio-lacustrine deposits coexisted, and the differences that arose concerned the proportion of these different lithologies over time (Liu et al, 2018a), which has been confirmed by various geological records (Ding et al, 2021; Shu et al, 2021).
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