Dolomite abundance in Chinese loess deposits: A new proxy of monsoon precipitation intensity

Abstract

Dolomite of detrital origin in carbonate‐rich soil can help indicate the intensity of carbonate dissolution and leaching processes. Using Fourier transform infrared spectroscopy, we generated a high‐resolution record of dolomite and calcite contents from eight sections on the Chinese Loess Plateau spanning the last 130 kyr. Based on the relative abundance of calcite and dolomite, four dissolution phases of carbonate minerals related to summer monsoon (SM) variations are identified as follows: (1) coexistence of dolomite and calcite indicating a very weak SM with a mean annual precipitation (MAP) < 610 mm; (2) calcite without dolomite indicating a weak SM, 610 < MAP < 690 mm; (3) both dolomite and calcite are absent, but there is no downward leaching indicating a strong SM, 690 < MAP < 725 mm; and (4) both dolomite and calcite are absent, and downward leaching of the underlying loess layer suggesting a very strong SM with MAP > 725 mm.

Distant Taklimakan Desert as an Important Source of Aeolian Deposits on the Chinese Loess Plateau as Evidenced by Carbonate Minerals

“…During the weakly weathered substages (Marine Isotope Stages (MIS) 5 b and d) in the last interglacial, the dolomite and total carbonate contents are close to those in the last glacial period (Figure ) in the western Jingyan section (Meng et al, ), which is a very weak weathered period also supported by low magnetic susceptibility (Meng et al, ) and high δ 13 C of bulk carbonate (Sun et al, ; Sun et al, ). This suggests that the initial total carbonate and dolomite content is generally constant during the glacial‐interglacial cycles (Meng et al, ), which is indicated by uranium comminution age (Li et al, ), Sr‐Nd isotopic compositions (Wang et al, ; Zhang et al, ), and high‐resolution age spectra of detrital zircons (Fenn et al, ). For the Pleistocene epoch, the mean total carbonate content in the loess layers of the LC section (Meng et al, ) is close to its average value of the last glacial in the six sections (Figure ).…”

“…Typical samples were dry sieved to obtain the <63‐μm (similar to the loess grain size range; Yang & Ding, ), 63‐ to 150‐, and >150‐μm fractions in order to evaluate carbonate distribution in the fine‐ and coarse‐grained fractions. For loess samples, the last glacial Jingtai section (37.46°N, 103.79°E) was sampled, and carbonate investigations were performed by Meng et al () in additional five sections (Figure ) over the last glacial cycles across the CLP, including Jingyan, Huanxian, Pingliang, Xifeng, and Luochuan (LC) sections as well as Pleistocene loess units (glacials) in the LC section referred to in Meng et al (; Figure ).…”

“…All samples were ground in an agate mortar to a powder‐like consistency before analysis. For the carbonate measurements using Fourier transformation infrared spectroscopy, the sample preparation was based on previously published procedures (Ji et al, ; Meng et al, ; Meng et al, ). We assume that approximately homogenous desert sand samples have detection limits of carbonate minerals similar to those of a loess matrix, ≤ 0.22% for dolomite and ≤0.13% for total carbonate (Meng et al, ).…”

“…Therefore, the Taklimakan Desert is a possible source of the CLP loess. To verify this hypothesis, we selected carbonate minerals (mainly consisting of dolomite and calcite) as tracers because previous scattered investigations found that they are mainly concentrated in the Taklimakan Desert (Li et al, ) and CLP (Meng et al, ). Therefore, carbonate minerals in the loess on the CLP are sensitive to dust contributions from the Taklimakan Desert.…”

Influence of Quaternary paleoclimate change on the permeability of the loess–paleosol sequence in the Loess Plateau, northern China

“…Dust carried by wind has a similar mineral composition to its source, but the minerals exposed to atmosphere undergo physical or chemical weathering due to thermodynamic instability (Liu, 1985;Balsam et al, 2004;Ji et al, 2001Ji et al, , 2009Meng et al, 2015). Calcite can be both primary (i.e.…”