The Middle and Late Pleistocene loess-soil record in the Iskitim area of Novosibirsk Priobie, south-eastern West Siberia

Abstract

The Pleistocene loess-soil sequence from West Siberia has provided a continuous record of Quaternary climate change in Northern Asia. The Middle-Late Pleistocene loess-paleosol stratigraphy of West Siberia has become recently a subject of discussion after a considerable revision was suggested by equating the Shipunovo pedocomplex to the Late Pleistocene stage 5 (MIS 5) instead of the previous correlation with the Middle Pleistocene stage MIS 9. The revision, however, was made using data from a single sampled section (Marble Quarry site), without proper reference to the local geology, to links of the loess and soil units traceable between the Lozhok and Marble quarries, and to deposition hiatuses. We compare the loess-soil stratigraphy at the Marble Quarry site (Iskitim area, Novosibirsk Priobie Plateau, upper Ob reaches) with the continuous record of the nearby Lozhok Quarry and evidence from boreholes in the quarry bottom to show that the Shipunovo pedocomplex does correlate with MIS 9. MIS 5 is the time of the Berdsk complex formation. The two complexes have many features of difference: thickness and maturity of soil profiles; thickness and expression of humus and illuviation horizons; distribution of calcium carbonate concentrations within the soil profiles; patterns of soil formation processes and cryoturbation, and stratigraphy. The Lozhok Quarry section, comprising five pedocomplexes intercalated in loess, is continuous and almost free from hiatuses. The Marble Quarry section in the Berd high terrace, in contrast, does not contain some stratigraphic units (including the Berdsk and Koinikha pedocomplex), the gaps being indicated by coarse sand and gruss at the base of loess layers. Therefore, the study has demonstrated the previously suggested Pleistocene loess-soil stratigraphy in southeastern West Siberia.