Lipid biomarkers in the Zoigê-Hongyuan peat deposit: Indicators of Holocene climate changes in West China

Lipid biomarkers extracted from a peat core obtained from the northeast edge of the Tibetan Plateau have provided a 13 kyr record of regional climate change. A period of warmer climate corresponding to the Holocene Optimum between 9 ka and 5 ka is evident in greater alteration of n-alkanoic acids and n-alkanols and in the appearance of biomarkers indicative of greater microbial activity. Concomitant increases in local precipitation that raised the water level of the peat bog are recorded by increases in the proportions of C23 and C25n-alkanes that are mainly derived from submerged/floating plants. Alternations in submergent and emergent plant n-alkane proxies reveal multi-decimeter scale rises and falls in the bog water level that relate to variation in precipitation on the Tibetan Plateau during the Holocene. Major low water level events occurred around 12.6, 11.3, 10.7, 9.4, 8.3, 6.0, 4.5, 3.1, 2.1 and 1.0 ka. These events correlate well with cold dry events recorded in same region from other climatic proxies that reflect millennial-scale Holocene instability in the Asian monsoon system. Our biomarker results also indicate that peat accumulation and preservation on the Tibetan Plateau are more sensitive to variability in monsoonal precipitation than in annual temperature.