Applications of Geochemistry to Paleoenvironmental Reconstruction in Southern Siberia

Abstract

This study presents results of paleoclimatic reconstructions during the Holocene in Southern Siberia and Central Asia by means of a geochemical approach. For investigations the deposits of Kutudjekovo Lake (Minusinsk Depression), White Lake (Uyuk Depression), aeoline-paleosoil deposits from Arzhan -2 monument (Uyuk Depression) and loess-paleosoil deposits from Tepsey cross-section (Minusinsk Depression) were sampled. The determination of chemical composition was done by ICP-AES, SNC analysis and the Wesemael method. X-ray diffraction was applied for determination of clay compositions in the deposits. The granulometric composition was determined by means of the grain-size analysis. The correlation analysis and method of principal components was applied for processing. Radiocarbon dating and archaeological dating were applied for determination of age of the deposit. The results allow the possibility of reconstructing the climatic factors, affecting the sedimentary processes. The investigations showed the differences of local paleoclimatic conditions between Minusinsk and Uyuk depressions during the Holocene. The Uyuk Depression is characterized by warmer and drier paleoclimate, while the climate in the Minusinsk Depression was milder and damper. Most likely the landscape features of these depressions influenced the local climate. The synchronous climatic variations during the Holocene can be noted for both depressions. These developments have correlation with paleoclimatic events in the Mongolia region. On the whole, the climate in the period from 5000 years ago to 3000 years ago can be characterized as dry. About 3000 years ago in a cold climatic period the rise in humidity began. The humidity maximum was around 2500 years ago (1st millennium BC). The period from 2500 to 1500 years ago was most humid and warm.The differences in occupation of the depressions by ancient people, probably, were linked to their paleoclimatic peculiarities. The occupation processes in the Minusinsk depression were more intensive and more diverse, then in the Uyuk depression. The abrupt increase of humidity, which was dated to about 2500 years ago in both areas, probably, resulted in the appearance of numerous tribes of the Scythian culture over the whole territory.Key wordsinorganic and organic geochemistrygeochemical indicatorsenvironmentsHolocenepaleoclimateSouthern SiberiaCentral AsiaScythian time