黄土高原东缘晚全新世高精度高分辨率石笋古环境记录

An Absolute-dated High-resolution Palaeoclimate Record Between 4400 and 150 a B.P.from Dragon Cave,Eastern Loess Plateau,China

基于山西武乡太行龙洞一支石笋5个230Th年龄和190个氧同位素数据重建4 400~150 a B.P.高分辨率δ18O序列。石笋δ18O值逐渐增加,除最近约600 a外,在千年尺度长期趋势变化上与中国南部其它洞穴记录相一致,表明晚全新世亚洲夏季风强度持续减弱响应于同一驱动机制。一次显著的气候突变事件发生在2 550~2 000 aB.P.,与史料记载的干旱期大致相对应。功率谱分析揭示出106 a周期,与树轮Δ14C太阳活动周期大体一致,说明百年尺度上太阳活动与东亚季风变化有一定关联性。

The Dragon Cave （38°46＂N, 113°16＂E） is located at transition between semi-humid and semi-arid ar- eas in the middle temperature zone of China. Here, mean annual temperature is 8℃. Mean annual rainfall is 530mm and about 87% of annual precipitation falls in May-October. Dragon Cave is 〉600m long with an ele- vation of 1400m on the western slope of Taihang Mountain, near the eastern edge of Chinese Loess Plateau. Stalagmite L1 was collected 200m from the cave entrance in December 2010. It is about 200mm like a candle. A total of 5 sub-samples were measured by an inductively Multi-collection coupled plasma mass spectrometry on a Finnigan-NEPTUNE in the High-precision Mass Spectrometry and Environment Chang Laboratory, De- partment of Geosciences, National Taiwan University. The uncertainty of reported age is ＋ 2σ. A high-resolution oxygen isotope profile established with 190 oxygen isotope data, provides a continuous history of East Asian summer monsoon intensity for the period of 4400-150a B.E （before AD1950）. With a relatively stable boundary condition, we interpret the 8^18O of speleothem calcite as most indicative of the amount of summer monsoon precipitation, although temperature and other factors might have some minor im- pact. Comparison of the record with previous published contemporaneous China stalagmite records shows that all 6^18O records, characterized with increasing 8^18O and declining summer monsoon precipitation trends over the late Holoeene, generally follow insolation changes on millennial timescale. This long-term agreement sup- ports that the solar insolation is the primary factor driving Asian summer monsoon. An unusual abrupt weak summer monsoon at 2550-2000a B.E indicates a mega-drought event, supported by historic archives. The spec- tral analysis of δ^18O time series yields a solar activity-related 106-yr periodicity. However, comparing to a weak solar activity at 2.7ka B.P., a 100-200-yr lag of the cave-inferred mega-drought event implies a compli- cated mechanism of short-term solar forcing on monsoon System.