Organic carbon isotope records of paleoclimatic evolution since the last glacial period in the Tangjia region, Tibet

Abstract

We firstly present the description of the river terrace at Tangjia (唐家) Village in Lhasa, Tibet, collect soil samples, and select the climate indicators including δ 13 C, total organic carbon (TOC), and the Rb/Sr ratios to study its paleoclimate in this area. Ancient climate changes have been reconstructed since the last glacier period. The results show that the δ 13 C, TOC, and the Rb/Sr ratio are good indicators of ancient climate fluctuations. Paleoclimatic evolution in the Lhasa Tangjia region could be divided into seven stages. In stages II (11.7-10.2 kaB.P.) and IV (8.1-6.1 kaB.P.), δ 13 C was positive and TOC was high, indicating that the climates in these two stages were relatively warm and humid. In stages III (10.2-8.1 kaB.P.) and V (6.1-4.9 kaB.P.), δ 13 C showed cyclical fluctuations, but TOC exhibited less change, suggesting that the climates displayed variation on the millennial scale. Moreover, the climatic variations were on a century-long scale during the later Middle Holocene. Compared with δ 13 C from Sumxi Co (松木希错) and δ 18 O from the Guliya (古里雅) ice core, the study confirmed that four cold events occurred during the Holocene (9.4, 8.2, 5.4, and 4.2 kaB.P.). The climate indicators were limited to the river terrace based on the geological characteristics of the Lhasa region. Unexpectedly, δ 13 C was a sensitive indicator of climate change. KEY WORDS: organic carbon isotopes, TOC, paleoclimate, Lhasa.

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