High-resolution peat humification records were obtained from Dajiuhu of the Shennongjia Mountains and Qianmutian of the Tianmu Mountains to study climate changes in East China.The analyses of pollen,organic matters,TOC,and Rb/Sr indicate a high degree of peat humification and thus strong decomposition of organic matter when climate was dry.Conversely,when climate was humid,the degree of humification is low because peat was preserved in a waterlogged condition.Peat humification from Dajiuhu occurred not only during the Younger Dryas(about 11.4-12.6 cal ka BP),the Blling-Allerd Warm Period(12.6-15.2 cal ka BP),and the Oldest Dryas(about 15.2-16.0 cal ka BP),but also during the early Holocene(about 11.4-9.4 cal ka BP),the 8.2 cal ka BP cold event,and the Holocene Optimum(about 7.0-4.2 cal ka BP).Both peat humification records since nearly 5 ka BP are consistent,showing that mountain peatland has synchronous responses to the East Asia monsoon-induced precipitation.The LOI data confirm the above observation.The monsoon precipitation since nearly 5 ka BP recorded in these two peat profiles can be divided into three phases.During 4.9-3.5 ka BP,precipitation amount was high but fluctuated greatly.During 3.5-0.9 ka BP,precipitation amount was low.During 0.9-0 ka BP,degree of humification reduced gradually,indicating the increase of monsoon precipitation.Contrast to other high-resolution records from East China monsoon region shows that the monsoon precipitation records of the two peat profiles since nearly 16 ka BP are controlled by a common forcing mechanism of summer solar radicalization in the Northern Hemisphere.
MA ChunMeiZHU ChengZHENG ChaoGuiYIN QianZHAO ZhiPing
重庆中坝遗址地层Rb、Sr、Hg及TOC研究表明:Rb、Sr和Rb/Sr值较好地反映了约4250 a B.P.以来气候变化过程,主要干冷期可与敦德冰川δ18O曲线谷值、湖光岩沉积物磁化率和Ti曲线峰值、以及大气14C浓度峰值和太阳活动水平较长期变化的低谷对比,反映出地层中Rb、Sr不易受人类活动干扰的特性。结合考古遗存对比还发现,Hg、P、Ca、Mg和TOC记录了该遗址约4250 a B.P.以来人类活动的三个不同演变阶段。进一步研究认为,盐业遗址的衰落可能与洪水事件。
