Paleoclimatic fluctuations inferred from leaf wax n-alkane records in Central Tibet in the late Oligocene to early Miocene

Climatic variations and their forcing mechanisms in Tibet are highly significant for understanding the environmental effects of the Tibetan Plateau through its controlling on atmospheric circulation. Here we present new leaf wax n-alkanes from Cenozoic lacustrine sediments in the Lunpola Basin of central Tibet to constrain long-term paleoclimatic changes. Our results suggest that the paleoclimate from the late Oligocene to early Miocene was generally stable, but tending slightly towards cold-dry from 25.5 to 23.2 Ma, followed by a trend towards warm-humid between 23.2 and 21.7 Ma, and finally by a more arid and highly oscillating climate after 21.7 Ma. Our results compare favorably with the proxies of marine delta O-18 records, which suggests that the general long-term trend since the late Oligocene has been a response to global temperature variations. Moreover, spectral analysis of delta C-13(31) and delta H-2(31) data reveals that relative humidity exhibits similar to 400 kyr cycles, controlled mainly by periodic changes in global ice volumes.