Correlation of loess–paleosol sequences in East and Central Asia with SE Central Europe: towards a continental Quaternary pedostratigraphy and paleoclimatic history

Abstract

As recent small climatic fluctuations on a 10 2–10 3 year time scale can be correlated worldwide, and represent a decline of mean annual temperature of only ⩽1°C, major climatic changes on at least a 10 5 year scale (glacial-interglacial cycles) and probably a 10 4 year scale (the approximate length of an interglacial) must be of similar ages throughout the temperate climatic belt of the Northern Hemisphere. This concept allows continental pedostratigraphical correlations. Detailed knowledge of the genesis of paleosols is needed to establish loess–paleosol stratigraphies that can be used for paleoclimatic reconstruction. Most paleosols, however, are truncated and largely recalcified from overlying loess. Micromorphological studies allow primary and secondary carbonates to be distinguished and provide unequivocal evidence of clay illuviation. This enables the recognition of typical loess, weathered loess and the recognition of different genetic soil horizons, such as CB, BC, Ah, Bw and Bt horizons. For the Brunhes epoch, the sequence at Karamaydan, Tadjikistan, is more detailed than the corresponding section in Luochuan, China, and even more than in SE Central Europe except for the last glaciation. The very good correlation with the deep-sea oxygen isotope record, which includes the development of an accurate astronomical time scale, allows a detailed chronostratigraphical subdivision of the loess–paleosol sequence in Karamaydan, which therefore should be regarded as a key sequence for reconstructing the climatic history of the Brunhes epoch. This implies that the loess–paleosol sequences in SE Central Europe are less complete than thought earlier. Pedocomplexes in Karamaydan correspond with single paleosols in SE Central Europe, e.g. the F6 paleosol in Stari Slankamen correlates with pedocomplexes PK VI and V at Karamaydan, which were formed over a period of about 140 ka , although pedogenesis was interrupted several times by loess deposition. The F6 soil is therefore an example of a welded paleosol, as are the F5, the F4 and the F2 paleosols in SE Central Europe. For most of the Matuyama epoch, the central and lower parts of the sequence at Chashmanigar show more pronounced paleosols than the equivalent parts at Luochuan; in SE Central Europe only at Stari Slankamen are three strongly developed though truncated paleosols (F9–F11) above Neogene sediments. Mineralogical investigations of the silt and clay subfractions show that there is little difference in the type and amount of pedogenic clay mineral formation between the Holocene soils and the paleosols of the Brunhes epoch at Karamaydan and of the Matuyama epoch at Chashmanigar. This suggests that the interglacial climates represented by the B or Bt horizons of the buried paleosols of late, middle, and early Pleistocene age were similar to that of the Holocene.