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Previous multi-proxy records have revealed the advantages of well-preserved and long-scale geological archives from the lake sediments of Barkol Lake, which is located at northeast Xinjiang in northwest China. However, the exact organic matter (OM) sources in the sediments and their response to climatic variability still remain unclear in this area. In this study, we present an 8.8 kyr n-alkane record extracted from the sediments in Barkol Lake to explore the OM sources and the relationship between n-alkanes and climatic changes. The results indicate that the n-alkane composition was dominated by long-chain n-alkanes(C27–C31), implying a dominant origination of OM from the terrestrial higher plants and emergent aquatic plants. The n-alkane data further revealed that changes in OM sources were related to the surface erosion-transportation-deposition processes controlled by climatic changes. Lake level changes, which are also regulated by climate conditions, played an important role in impacting OM accumulation. Relatively wetter conditions would result in a rising lake level that favored more aquatic OM and less terrestrial OM input, and vice versa. The regional climate patterns have been generally dominated by alternations of cold-wet and warm-dry episodes over the past ~8.8 kyr. We preliminarily concluded the dynamic changes of OM input and the hydrological changes in Barkol Lake was mainly controlled by SSTs in the North Atlantic region and melting water supply modulated by Eurasian ice sheet. [ABSTRACT FROM AUTHOR]

In this study, we used a ~47.0-kyr record of Sr–Nd isotopic data derived from lake sediments in Dahu swamp in the eastern Nanling Mountains to explore the possible changes in the source of sediments, and to provide insights into the East Asian winter monsoon (EAWM) driven climatic signals. Based on Sr–Nd isotopic results, we argued that local weathered granitic residues were the dominant source of sediments throughout the past ∼47.0 kyr. However, variations of 87Sr/86Sr and 144Nd/143Nd ratios were likely disturbed by the mixture of an additional input from Chinese Loess Plateau (CLP). During some dry/cold millennial periods (e.g., Heinrich event 5, 4, and 2, and the 26.0–24.0 kyr B.P), similar Sr–Nd isotopic signatures between the lake sediments and the fine fraction (<20 μm) of the loess from CLP implied an aeolian dust source. Thus, variability of Sr-Nd isotopic ratios indirectly indicated two modes of climate patterns: the wet and warm intervals during which the sediments were mainly derived from the local weathered residues were expressed in increased 87Sr/86Sr and decreased 144Nd/143Nd ratios, whereas during the dry and cold intervals the increased input of fine dust from CLP transported by strengthened EAWM winds would favor declined 87Sr/86Sr and increased 144Nd/143Nd ratios. Our Sr‒Nd isotopic records revealed an anti-phase between the EAWM and the summer monsoon, and displayed a good consistency with the record of mean grain size of quartz of loess from CLP, which was regarded as a reliable proxy of EAWM, suggested they can indirectly reflect variability of EAWM strength. [ABSTRACT FROM AUTHOR]

Chondrite‐normalized rare earth element (REE) data of a ~47.0‐ka lake sedimentary sequence from the Dahu Swamp in the eastern Nanling Mountain area were used to determine climatic variations within the region. These sediments proved to be valuable proxies of climatic changes and their origin is discussed. The influences of grain size, organic matter absorption and Fe‐Mn oxides on REE composition were determined to not be significant. The dominant source of sediments was ascertained to be the weathered granite residues from the catchment, enriched in light rare earth elements (LREE). Intensified East Asian summer monsoon (EASM) resulted in intensive chemical weathering, leading to enhanced REE and LREE fractionations in the weathered residues; this caused the increase in REE and LREE, and decrease in heavy rare earth element (HREE) fractionation degrees in the sediment. Therefore, our results indicate that changes in LREE/HREE, (La/Yb)N, (La/Sm)N) and (Gd/Yb)N, the proxies of REE, LREE, and HREE fractionations, can serve as proxies of regional climate‐induced chemical weathering and thus serve to constrain EASM changes. [ABSTRACT FROM AUTHOR]

This study provides a 16.2-kyr record of mercury (Hg) deposition derived from a lacustrine sedimentary sequence in Dahu Swamp, eastern Nanling Mountains. Results indicate that changes in climatic conditions had a significant effect on Hg concentrations (Hg – C) and accumulation rates (Hg -AR). Multi-proxy records including dry density, grain size, geochemical elements, organic matter and pollen indicators were compared with Hg accumulation. The results revealed that the contributions of detrital input and atmospheric deposition were minor, and Hg accumulation in the sediments was closely related to changes in climatic conditions: relatively drier and colder climate would result in shrinkage of the lake water body thus favoring increased formation of organic-rich peat or gyttja and leading to enhanced absorption of Hg by organic matter and result in increases of Hg – C and Hg -AR in sediments, and vice versa. Our results indicate that variations of Hg accumulation in Dahu Swamp were greatly impacted by climate under the influences of solar insolation changes and shrinkage or expansion of ice sheets in high latitudes to the north. The results of this study provide an insight into the response of Hg accumulation to low latitude climate processes in the East Asian summer monsoon region. [ABSTRACT FROM AUTHOR]

Previous multi-proxy records have revealed the advantages of well-preserved and long-scale geological archives from the lake sediments of Daping swamp in the western Nanling Mountains in South China. However, the exact organic matter (OM) sources in the sediments and their response to climatic variability still remain unclear. In this study, we present a 15.3-kyr n -alkane record extracted from lacustrine sediments in this swamp to explore the OM sources and the relationship between OM input and climatic changes. The results indicated that the n -alkane composition in sediments was dominated by long-chain n -alkanes (C 27 -C 31), implying that the OM mainly originated from the terrestrial higher plants and emergent aquatic plants. The n -alkane data further verified that changes in OM sources were related to the surface erosion-transportation-deposition processes controlled by climatic changes. Lake level change, which was also regulated by climate conditions, played an important role in impacting OM accumulation; warmer and wetter conditions would result in rising lake levels that favored more aquatic OM and less terrestrial OM input, and vice versa. Variability of the Asian summer monsoon intensity regulated by the dynamic variations in low-latitude processes (e.g., solar insolation, intertropical convergence zone, and El Niño/Southern Oscillation), as well as high-latitude processes (e.g., meltwater input in the North Atlantic), was closely related to the OM accumulation in sediments. • A 2.36-m n -alkane records from the subalpine Daping Swamp in western Nanling Mountains (South China) were reported. • n -Alkane proxies revealed the OM source mainly originated from terrestrial higher plants and emergent aquatic plants. • The OM accumulation is closely related to climatic/environmental conditions. • The warm and wet conditions favor increased aquatic/autochthonous and decreased terrestrial/allochthonous OM input, and vice versa. [ABSTRACT FROM AUTHOR]