泥河湾盆地东部中全新世晚期的干/冷干事件与中全新世湿润状况的结束

Dry/cold-and-dry Events of the Late Mid-Holocene and Termination of the Mid-Holocene Wet Conditions in the Eastern Part of Nihewan Basin

对取自泥河湾盆地东部化稍营镇 (114°36′E ,40°18′N)附近一剖面以泥炭为主的沉积物做了AMS 1 4 C测年、粒度、碳酸钙含量、碳酸盐中δ1 8O和δ1 3 C组分、有机质含量、TOC、C N分析以及 χlf和SIRM测量。结果表明 ,这些沉积物大致是在 5 32 0～ 3 370aB .P .堆积的 ;在 5 32 0～ 3 6 0 0aB .P .,气候仍较为湿润温暖 ;在 36 0 0～346 0aB .P .和 3 430～ 3 40 0aB .P .,有两次明显的干 冷干事件。气候的这种波动 ,可能是中全新世湿润状况的结束过程。

AMS 14C dating, analyses of grain-size, CaCO 3 content, δ 18O and δ 13C in carbonates, content of organic matter, TOC content and C/N ratio, and measurements of χ lf and SIRM are performed with sediments, consisting mainly of peat, from a profile near Huashaoying Town (114°36′E, 40°18′N), the eastern part of Nihewan Basin. The results indicate that these sediments were deposited mainly during 5320-3370 a B.P.; the climate was still rather humid and warm during 5320-3600 a B.P.; there was a marked dry/cold-and-dry event occurring respectively at 3600-3460 a B.P. and 3430-3400 a B.P. Such climatic fluctuations might be the terminating process of the mid-Holocene wet conditions.