Strontium isotopic and elemental characteristics of calcites in the eolian dust profile of the Chinese Loess Plateau during the past 7 Ma

Abstract

Strontium isotopic ratios, calcium and strontium contents of calcites in the eolian dust profile during the last 7 Ma at Lingtai were systematically studied. 87 Like Ca contents, Ca/Sr ratios in the Tertiary red clay are close to those in the Quaternary loess. Elemental ratios and contents have different variations from the Sr isotopic ratios of calcites in the Lingtai profile, implying that isotopic ratios were better proxies for climate change than elemental ratios and contents. Primary carbonate and silicate comprised two endmembers determining the range of the Sr isotopic ratios of calcites, and chemical weathering was an inner driver to induce strontium isotopic variations of calcites in the eolian dust profile. Our isotope data indicate that chemical weathering was strongest in the Tertiary red clay, the second in the Quaternary paleosols, and weakest in the Quaternary loess. Strontium isotopic variations of calcites are in a good agreement with pedogenic characteristics in the Lingtai profile, broadly consistent with a proxy of the summer monsoon-Fe 2 O 3 (f)/Fe 2 O 3 (t) ratios, and correlate with variations of Fe 2+ / Fe 3+ ratios in the Lingtai profile and the dust flux in ODP885/886 during the late Cenozoic. Strontium isotopic variations of calcites are different from the magnetic susceptibility records in the Lingtai profile, further demonstrating that magnetic susceptibility of the Tertiary red clay could not reliably indicate the Tertiary summer monsoon.As a result, strontium isotopic characteristics of calcites in the Lingtai profile indicate that the Quaternary summer monsoon had a glacial-interglacial alternation and weakened with large-amplitude oscillations since 0.5 Ma B.P., and also reveal that the Tertiary summer monsoon was more stable and overall stronger than the Quaternary, nevertheless, similar climates to those in the Tertiary probably occurred during a few paleosol developments of the Quaternary.

Sr isotopic and elemental characteristics of calcites in the Chinese deserts: Implications for eolian Sr transport and seawater Sr evolution

“…Sr concentrations of calcites in the deserts mainly depended on primary carbonates (marine carbonate) and thus probably have not had a great fluctuation over the past 2.5 Ma. In addition, 87 Sr/ 86 Sr ratios of calcites in the loess-paleosol profile at Lingtai during the past 2.5 Ma have a narrow range from 0.710433 to 0.711683 with a mean of 0.711149 (Rao et al, 2008b). This average value is nearly identical to the calcite 87 Sr/ 86 Sr ratios in Asian dust entering the NPO recommended by Jacobson (2004).…”

“…The four deserts (Taklimakan, Qaidam, Badain Jaran, and Tengger) have calcite 87 Sr/ 86 Sr ratios from 0.7095 to 0.7132 with the highest values for the Tengger, and the lowest for the Taklimakan ( narrow range of 0.7104-0.7117 (Rao et al, 2008b). In general, chemical weathering is stronger in the CLP than in the deserts, because the rainfall and solar radiation increase from the deserts to the Chinese Loess Plateau of northern China.…”

“…Pedostratigraphy, magnetic susceptibility, grain size, mineralogy, and geochemistry of this profile have been investigated in detail (Ding et al, , 2001Gu et al, 1999;Sun and An, 2002;Gylesjö and Arnold, 2006;Wang et al, 2007;Rao et al, 2008b). The provenance of eolian calcite in the Loess Plateau and geochemical evolution of eolian calcite from source areas to the Loess Plateau are explored through geochemical comparison between the Lingtai profile and the deserts in this section.…”

Livestock supply to an imperial sacrificial site of the early Chinese empires evidenced by strontium isotope ratios

“…Thus, similar geochemical signals could be expected. The silicate fraction of the eolian deposits showed highly radiogenic characters with 87 Sr/ 86 Sr values greater than 0.7150 (Supplementary Table S4, Figure 8A; Bird et al, 2020;Chen et al, 2001;Sun, 2005), distinct from the accompanied calcite fraction, which has 87 Sr/ 86 Sr values generally lower than 0.7115 (Yang et al, 2000;Rao et al, 2008). Due to their differential erosion rate, an isoscape of the strontium composition of China based S4, Figure 8B), as well as the riverine water samples (Wang and Tang, 2020).…”

Small mammal tooth enamel carbon isotope record of C4 grasses in late Neogene China

“…Rea et al, 1998;Ding et al, 1999;Fortelius et al, 2002;Jia et al, 2003;Ma et al, 2005;Fortelius and Zhang, 2006;Wu et al, 2006;Wang et al, 2006;Kaakinen et al, 2006;Rao et al, 2008;Sun et al, 2010;Xing et al, 2012). The Late Miocene humidity of Northern China is in stark contrast to the global trend of mid-latitude drying at that time (Fortelius et al, 2002), and it seems to have created a favorable setting for the influx of immigrant herbivorous land mammals from several directions, and the later development of endemic taxa from both native and immigrant origin (Fortelius and Zhang, 2006;Mirzaie Ataabadi et al, 2013).…”