Climate and environmental changes during the past 19,000 years reflected d18O, d13C and scanning XRF elements of a 14C dated stalagmite from south Altai, Russia

Abstract

A 22-cm long stalagmite (L2) from Lunnaya Cave (52º41’ N, 88º44’ E, 481 m a.s.l.) located in south Altai mountains of Russia was dated by AMS 14C because 230Th/U dating was not successful due to low U but high Th contents. The stalagmite grew since 19 kyr BP with very slow rate before 12 kyr BP and a growth hiatus during 5.5~7 kyr BP. A total of 1150 samples have been measured for δ18O and δ13C, revealing climatic and vegetation changes under the influence of Westerly, Polar Front and Siberian High. Although the δ18O trends show a depletion trend from early Holocene to middle Holocene, reached the lightest values between 7 and 8.5 kyr BP, and then an enrichment trend from 7 kyr BP toward the late Holocene, the δ18O trends are complicated for interpretation of climatic conditions. High-resolution (0.2-mm interval) scanning XRF Sr/Ca, Fe and Ti profiles illustrate that the weathering condition of overlying soil and limestone bedrock had significant change from pre-Holocene to late Holocene. The long-term trends of δ18O and δ13C records were related to moisture source and seasonal precipitation. Thus, both δ18O and δ13C records are needed to be de-trended in order to reflect precipitation amount effect and vegetation development, being negative values representing wet condition with more abundant vegetation, and vice versa. The growth hiatus of the stalagmite during 5.5~7 kyr BP was probably due to arid condition. Based on the δ18O, δ13C and scanning XRF elemental records, the climatic condition was very cold with only summer-month stalagmite growth during 19-13 kyr BP; cold and dry between 13-12 kyr BP (Younger Dryas); wet during 12-11.5 kry BP; mainly dry between 11.5 and 9.5 kyr BP; mainly warm and wet between 9.5 and 7 kyr BP. During 2.8~5.5 kyr BP, the climate was strongly fluctuated on centennial scales around an average condition. Dry climates were prevailed during 2.8~1.8 and 1~0.2 kyr BP, whereas wet climates were dominated during 1.8~1 and 0.2~0 kyr BP. The climatic conditions shown by the stalagmite agree well with the lake records in western and central Siberia.