4.3 Statistics of C. pulveratrix and M. yantaiensis in loess-paleosol strata

In the Beiyao section, the maximum number of cold-aridiphilous snailsC. pulveratrix was 70, occurring at the depth of 9.7 m (belonging to MIS6). In contrast, the maximum number of sub-humidiphilous snailsM. yantaiensis was 34, appearing at the depth of 4.5 m (belonging to MIS3) (Figure 3). At the bottom of the interglacial paleosol S1, very few of land snail fossils were left because of the influence of strong pedogenesis. However, the other horizons in the section were rich in snail fossils. Therefore, without considering this factor, the cold-aridiphilous species C. pulveratrix had a certain number distributing from MIS2 to MIS7, with two most abundant horizons (with fossil number of 58 and 70) respectively in MIS4 and MIS6. The sub-humidiphilous species M. yantaiensis were mainly found in MIS3 and MIS7, with maximum number reaching up to 34 and 23, respectively. Moreover, when the number of M. yantaiensisincreased in some horizon, the number of C. pulveratrix in the same horizon or neigbouring horizons significantly reduced. Conversely, when the number of C. pulveratrix reached the peak of the stage, the number of M. yantaiensis approached the minimum or 0.