Variation of soil Δδ 13C values in Xifeng loess-paleosol sequence and its paleoenvironmental implication
Variation of soil Δδ13C values in Xifeng loess-paleosol sequence and its paleoenvironmental implication

The carbon isotopic compositions of soil organic matter (SOM) and total carbonate (TC) in Xifeng loess-paleosol sequence have been studied. The δ 13CSOM values vary from 23.8‰ to 20.2‰, which are higher in interglacial than in glacial stages. Contrary to δ 13CSOM values, the δ 13CTC values vary from 8.5‰ to 3.6‰ and are lower in interglacial than in glacial stages. The differences (Δδ 13C) between the δ 13CSOM and δ 13CTC values vary from 14.1‰ to 19.4‰. Our results from the Xifeng loess-paleosol sequence indicate that the Δδ 13C values represent the ratio of primary carbonate (PC) to secondary carbonate (SC). The Δδ 13C values were high in the loess stages, and the maximal PC-to-SC ratio can reach 6:4. But in the paleosol stages, the Δδ 13C values were low, with a small proportion of PC. The Δδ 13C values in loess-paleosol sequence also indicate the contributions of the dust to the loess sediment in the Chinese Loess Plateau because the dust contains the PC.