The Lipid Biomarker Holocene Paleoclimate Record of West China in the Zoige-Hongyuan Peat Deposit

Paleoclimate reconstructions based on lipid biomarkers from peat bogs are relatively uncommon, although this approach has been widely applied to lake sediments where it yields histories of climate-related changes in types of vegetation and organic matter preservation. We describe stratigraphic patterns in peat lipid biomarker distributions extracted from a well-dated peat core from the Zoige-Hongyuan peat bog. The bog is on the Qinghai-Xizang Plateau of west China on the northeast edge of the Tibetan Plateau and has accumulated a continuous deposit of peat during the latest Pleistocene and the Holocene. A period of warmer climate corresponding to the Holocene Optimum between 9 ka to 5 ka is evident in greater alterations of n-alkanoic acids and n-alkanols and in the appearance of biomarkers diagnostic of greater microbial activity. Changes in local precipitation that modified the water level of the peat bog are indicated by increases in the proportions of C23 and C25 n-alkanes that are mainly derived from submerged/floating plants. Alternations in submergent and emergent plant n-alkane proxies reveal millennial scale rises and falls of the bog water level in the Tibetan Plateau, thereby reflecting variations in Asian monsoon precipitation 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 by other climatic proxies. These results reflect Holocene instability in the Asian monsoon system. Our results indicate that millennial-scale variability in precipitation is more sensitive than temperature in reflecting Asian monsoon climatic dynamics on the Tibetan Plateau.