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An n-alkane and carbon isotope record during the last deglaciation from annually laminated sediment in Lake Xiaolongwan, northeastern China

Sun, Qing, Xie, Manman, Lin, Yuan, Shan, Yabing, Zhu, Qingzeng, Xu, Deke, Su, Youliang, Rioual, Patrick, Chu, Guoqiang
Journal of paleolimnology 2016 v.56 no.2-3 pp. 189-203
C3 plants, alkanes, biomarkers, carbon, climatic factors, deciduous forests, ice, lakes, latitude, limnology, macrophytes, monsoon season, oxygen, paleontology, sediments, stable isotopes, temperature, time series analysis, China, Greenland
The last deglaciation is of great interest because Northern Hemisphere climate has gone through several abrupt changes. We present an n-alkane and compound-specific carbon isotope record of the last deglaciation from the annually laminated sedimentary sequence of Lake Xiaolongwan, northeastern China. The n-alkane distribution suggests that the sparsely distributed vegetation prior to 14.7 ka BP, changed to wood plants and aquatic macrophytes in the early Bølling-Allerød, and was followed by a broadleaved deciduous forest after 11.4 ka BP. In this forest region, where the vegetation is dominated by C3 plants, the compound-specific δ¹³C value of the long-chain n-alkanes (nC₂₇, nC₂₉ and nC₃₁) is interpreted as a proxy of effective precipitation, while temperature might play a minor secondary role. The positive δ¹³C₂₇–₃₁ values during the Bølling-Allerød suggest a dry-warm climatic condition, while the negative δ¹³C₂₇–₃₁ at 13.0–11.4 ka BP indicates a cold-wet climate during the Younger Dryas in this region. Two periods with lower δ¹³C₂₇–₃₁ occurred at 16.1–16.5 and 17.3–17.7 ka BP and could be associated with the Heinrich event-1a and the Heinrich event-1b, respectively. The synchroneity between the biomarker time series in Lake Xiaolongwan and the δ¹⁸O record from the Greenland ice core suggest the dominance of high latitude processes on regional monsoon evolution from the last glacial, the Bølling-Allerød, the Younger Dryas to early Holocene. Regionally, the Okhotsk High might have played an important role for abrupt changes during the glacial/interglacial transition.