Glacial–interglacial change in chlorite concentration from the Lingtai section in the Chinese Loess Plateau over the past 1.2 Ma and its possible forcing mechanisms

Abstract

High-precision concentrations of chlorite minerals from the Lingtai section in the Chinese Loess Plateau and the surrounding deserts are presented through a mineral liberation analyzer technique. Variations in chlorite concentration over the last 0.5 Ma display a typical pattern of glacial–interglacial changes, with its bulk content in loess units approximately twice that in paleosol units. This climate-driven chlorite change is more pronounced in the fine-size fraction (5–20 μm) of the loess deposits. Evidence from changes in hornblende and muscovite along the same profile suggests that the glacial–interglacial oscillations were likely controlled by changes in atmospheric circulation and shifts in the dust provenance instead of postdepositional weathering. A relatively high chlorite content in several deserts near Mt. Qilian compared with the other desert basins suggests that a transport pathway in the west–east direction, associated with southward shifts of the winter monsoons, may play an important role in modulating the chlorite records. In addition, enhanced saltation and transportation of dust materials is thought to be a main driver of the pronounced changes in the fine-size fraction. Finally, we discuss a possible forcing mechanism behind different long-term trends between the chlorite and its secondary weathering products we observed here.

Changes in Paleovegetation and Climate Seasonality in Central China Over Last Two Glacial Cycles: A Stable Isotope Perspective From Land Snails

“…The three‐stage MIS3 can also be envisaged on the SUS curve of our loess section (Figure 3). This type of subdivision for MIS3 was in accordance with the study of land snail faunal assemblages in the middle part of the Chinese Loess Plateau (e.g., Chen & Wu, 2008). In addition, the average δ 18 O value of C. pulveratrix was −5.3‰ during the MIS3 stage.…”

“…This assemblage change indicated that the climate was warmer and more humid at early MIS3 than at late MIS3. A faunal assemblage study of land snails in the central Chinese Loess Plateau also suggested that the temperature and humidity were higher during early MIS3 (Chen & Wu, 2008). However, the δ 18 O value of C. pulveratrix was highly variable during early MIS3 and was not as low as that during late MIS3 (Figure 3).…”

“…The two species of land snails (Figure 2) used in this study have different living habits. C. pulveratrix usually lives in relatively cold and dry climates, whereas M. yantaiensis lives in warm and subhumid climates (Chen & Wu, 2008; Wu et al., 1996). This ecotype division for the two species is made based on their requirements on temperature and humidity at modern times (Wu & Li, 2008).…”

Geophysical sediment properties of a late Pleistocene loess–paleosol sequence, Chenarli, northeastern Iran

“…It is susceptible to weathering and provides free Fe for secondary ferrimagnetic mineral formation (e.g., Spassov et al, 2003; Torrent et al, 2007; Peng et al, 2014). Therefore, magnetic mineral concentration through lessivage, removal of carbonates (Singer et al, 1996), and chlorite weathering (He et al, 2018; Hyodo et al, 2020; Ye et al, 2020) are likely in these Bt(b) horizons. This might explain why high χ lf and χ fd % are observed in the Bt(b) horizons of loess–paleosol sequences in northern Iran.…”