Quaternary Research最新文献

Reconstructing the Mid-Holocene climate change in arid and semiarid areas can help predict regional moisture availability and resultant lake evolution and vegetation changes due to future warming. Here, we present a sediment core (YLH15A) from Moon Lake in the Tengger Desert, arid and semiarid China. Based on robust accelerator mass spectrometry 14C dating and multiproxy analyses (pollen, grain size, elements, and total organic carbon), we reconstructed regional climate changes since 7.6 cal ka BP. The climate was generally dry from 7.6 to 2.8 cal ka BP, as indicated by the dried-up lake, strong aeolian activities, and no vegetation, except for a short-term wet interval between 5.4 and 4.9 cal ka BP. The generally dry climate shifted after 2.8 cal ka BP, which is suggested by expanded steppe desert/steppe and increased vegetation cover; it was also accompanied by lake development, which was likely related to increased groundwater recharge originating from regional precipitation and temporary floods from adjacent mountain areas. Our results reveal a prolonged dry Mid-Holocene and relatively wet Late Holocene that are basically consistent with climatic records from the central–east Asian arid and hyperarid areas. The prolonged dry climate in the arid and hyperarid areas is likely to be related to high evaporation triggered by high temperatures during the Middle Holocene.

Although black soil in northeast China undergoes severe erosion, the contribution of parent materials, mainly Quaternary loess and non-loess sediments, to soil erodibility remains unclear. Considering the inheritance of ferromagnetic materials by parent materials, changes in magnetic parameters can successfully determine soil erodibility on a regional scale with a close climatic background. Here, we analysed the magnetic indicators of 142 samples from the black soil horizon formed on loess and non-loess sediments, covering areas of severe and slight erosion in the region to determine the effects of parent materials on the erodibility of black soil in northeast China. Both low-frequency magnetic susceptibility and frequency magnetic susceptibility (χfd) were proportional to the decrease in erosion rate due to erosion-induced leaching of ferromagnetic materials, and the change in χfd was narrow for black soil with loess parent materials, corresponding to relatively low soil erodibility. Compared with loess, the addition of soil organic matter could stabilise soils against erosion, thereby inducing a decrease in the erodibility of black soil formed on loess. Additionally, sustainable soil management policies to protect black soil from further erosion are necessary and urgent under the pressure of maintaining high grain yields and preventing erosion in northeast China.

Carbon isotope analysis of pedogenic carbonate (δ13CCarb) and soil organic matter (δ13CTOC) is widely applied in reconstructions of terrestrial paleovegetation. The δ13C of different archives is considered well matched and equally reflects the proportion of C3/C4 plant biomass covering the soil profile. However, modern soil and paleosol sequences provide substantial evidence that δ13CCarb and δ13CTOC do not always match, raising doubts about the accuracy of quantitative C4 plant reconstructions. Here we report paired δ13C records of pedogenic carbonates and organic matter occluded within carbonate nodules from the Shaozhai section in the central Chinese Loess Plateau (CLP). The δ13CCarb record exhibits a positive anomaly and exceeds the theoretical fractionation range with the coexisting δ13CTOC record during the expansion of C4 plants. The possibility of contamination by detrital carbonates and atmospheric CO2 affecting δ13CCarb was ruled out based on the morphological features, mineral fractions, and geochemical composition of carbonate nodules. Our study suggests that the enhanced respiration of C4 plants during pedogenic carbonate precipitation may have caused positive shifts in δ13CCarb records, supporting the hypothesis that the discrepancy in carbon sources explains the δ13CCarb positive anomaly. Thus, the δ13CCarb could reflect the maximum relative abundance of C4 plants during their metabolic peaks.

To further elucidate the Late Pleistocene glacial history of mid-elevation mountainous regions in Central Europe, 10Be cosmic-ray exposure (CRE) dating was applied to moraines in the Zastler Tal Valley in the Southern Black Forest. Periods of glacier recession from moraines in this valley began no later than 16 ka, 15 ka, and 13 ka. CRE ages of moraines in this and other parts of the Southern Black Forest cluster around 17–16 ka and 15–14 ka, thus suggesting a common forcing of glacier recession. Equilibrium-line altitudes (ELAs) during moraine formation were calculated for precipitation reconstruction. Observed spatial discrepancies in ELAs at ca. 15–14 ka are explained best by the size of snow-contributing areas. The reconstructed annual precipitation at the ELA for ca. 16 ka and ca. 15 ka is affected by large uncertainties, representing a wide range from ~50% to ~150% of present-day values. Due to various factors, such as drifting snow, the lower bounds of the estimates appear most realistic, thus concurring with the common hypothesis of less precipitation during the last glacial termination than today in Central Europe. Further research is needed before ELAs of small ice masses can be employed for precise precipitation estimates.