Distinctive white laminations appear in the generally black sediments of the anoxic, subalpine Great Ghost Lake in southern Taiwan. These white laminations have lower porosity, organic matter content and C/N ratio, bu...Distinctive white laminations appear in the generally black sediments of the anoxic, subalpine Great Ghost Lake in southern Taiwan. These white laminations have lower porosity, organic matter content and C/N ratio, but higher C/S, N/S ratios and magnetic susceptibility, and contain organic matter most probably derived from phytoplankton. This and the collision marks on the quartz particles suggest that they have an aeolian component and have been deposited in cooler and drier periods. The organic matter of the black sediments is mainly from land plants and the quartz particles bear no collision marks, suggesting local deposition under warmer and wetter climates. These high resolution data, the first not only in Taiwan but also for Southeast Asia, are in good agreement with the local climatological records deduced from documentary sources since 1681 and direct instrumental rainfall measurements at stations nearby since 1900. Rainfall over the past 2600 years has been reconstructed. Major droughts appear in 240 BC, 80 BC, 90 AD, 420-520 AD, 620-700 AD, 850-930 AD, 1350-1430 AD, 1570 AD, 1730-1800 AD and 1960 AD, and correspond to not only the periods of cold/dry and frequent dust storms but also major population declines based on the historical and natural records of China. These seem to reflect large scale climatic changes.展开更多
文摘Distinctive white laminations appear in the generally black sediments of the anoxic, subalpine Great Ghost Lake in southern Taiwan. These white laminations have lower porosity, organic matter content and C/N ratio, but higher C/S, N/S ratios and magnetic susceptibility, and contain organic matter most probably derived from phytoplankton. This and the collision marks on the quartz particles suggest that they have an aeolian component and have been deposited in cooler and drier periods. The organic matter of the black sediments is mainly from land plants and the quartz particles bear no collision marks, suggesting local deposition under warmer and wetter climates. These high resolution data, the first not only in Taiwan but also for Southeast Asia, are in good agreement with the local climatological records deduced from documentary sources since 1681 and direct instrumental rainfall measurements at stations nearby since 1900. Rainfall over the past 2600 years has been reconstructed. Major droughts appear in 240 BC, 80 BC, 90 AD, 420-520 AD, 620-700 AD, 850-930 AD, 1350-1430 AD, 1570 AD, 1730-1800 AD and 1960 AD, and correspond to not only the periods of cold/dry and frequent dust storms but also major population declines based on the historical and natural records of China. These seem to reflect large scale climatic changes.
