The Loess-Paleosol Sequence at the Krasnogorskoye Section, the Low-Hill Zone of the Northeastern Altai Mountains

The loess-paleosol sequence of the Krasnogorskoye section in the low-altitude area of the northeastern Altai Mountains, can provide a yardstick for estimating the age of the Paleolithic sites and reconstructing environmental and climatic changes. Its correlation with the respective sequence of the southern part of the West Siberian Plain is evaluated. Five pedocomplexes are studied in detail, evidencing the evolution of the Middle and Late Pleistocene soil formation from the Shadrikha interglacial to the Karga interstadial. Buried soils of the Shadrikha, Shipunovo, Koinikha, and Kazantsevo warm stages formed under a climate that was warmer and more humid than today. After the Kazantsevo interglacial, both the range and the frequency of climatic oscillations show marked changes. It is demonstrated that the warm stages of this interval differ from the earlier ones by lesser warming and shorter duration by a cooler and more arid climate. Seven loess horizons dividing pedocomplexes are established. Nonmetric and metric analyses of quartz sand grains support the eolian origin of loess horizons under cryoarid conditions. The size of grains in the Late Pleistocene portion of the Krasnogorskoye section attests to the intensifi cation of the loess processes. Higher magnetic susceptibility during the cool stages and higher frequency-dependent susceptibility during the warm stages evidence marked climatic oscillations. After the Kazantsevo interglacial, the amplitude fades and the pattern of paleoclimatic signal recorded by the magnetic properties of loess and paleosol in the section are close to the “Alaskan” type.