Loess stratigraphy of Central Asia: Palaeoclimatic and palaeoenvironmental aspects

The loess-palaeosol succession of Central Asia is comparable with that of the Loess Plateau in North China. Palaeomagnetic investigations and palaeontological studies in South Tadjikistan suggest a date o 2-25 Ma for the oldest loess, indicating that dust storms became frequent in the region since 2-2.5 Ma BP. Under the prevalently arid and semi-arid environments of Central Asia aeolian processes had a gradually increasing influence on subaerial sedimentation during the Pleistocene. However, atmospheric aeolian processes in Central Asia have mainly developed in accordance with Pleistocene climatic cyclicity, without extremely high intensification during the late Pleistocene as implied by the previous TL dating results. The identification of loess and palaeosol horizons with respective glaciations and interglacials is sometimes disputable. Nevertheless the available data in spite of limited evidence, characterise well-developed palaeosols of the middle and late Pleistocene, as warm and wet intervals associated with interglacials. Palynological studies of loess sections show that loess and palaeosol horizons have palynological spectra that are sometimes difficult to interpret. Interregional loess-palaeosol correlation with glacial-interglacial events as well as with oxygen isotope records should be supplied by multidisciplinary investigations.