Geochemistry of the holocene sediments of Lake Chenghai, SW China, and its implications for paleoenvironmental reconstruction

摘要

Analysis of lake sediment geochemistry is valuable for understanding past hydroclimatic changes via the reconstruction of changes in catchment erosion, chemical weathering, redox processes and the intensity of evaporation. In this study, we analyzed the geochemical composition, magnetic susceptibility and carbonate content of the Holocene sediments of Lake Chenghai in the Jinsha River valley, southwest China. Our aims were to determine the influence of Holocene hydroclimate evolution and geo-hazards on lacustrine sedimentation. The results show that the hydroclimate was generally humid during 7.57-4.65 cal ka BP, and that subsequently it became relatively dry during 4.65-1.37 cal ka BP. Our results also reveal that the centennial scale variability of the lake level during the Holocene is forced by changes in solar activity and oceanic-atmospheric feedback. In addition, the interval of 3.31-1.95 cal ka BP was the driest, due to highly variable and intense El Nino events, and the southward migration of the intertropical convergence zone. Furthermore, three large landslide events occurred at 7.30, 6.36 and 0.76 cal ka BP around Lake Chenghai, which are correlated with unusually large floods during the period of weakened monsoon activity, and/or with earthquake events.