作　　者： ; ; ; ; ;

机构地区： 陕西师范大学历史文化学院西北历史环境与经济社会发展研究中心

出　　处： 《海洋地质与第四纪地质》 2005年第4期107-113,共7页

摘　　要： 河北平原中部任丘剖面厚达12 m的河湖相沉积和多层的泥炭为该地区环境演变研究提供了基础.根据测年结果、沉积物的粒度、磁化率等代用指标分析,重建了该地区11 640 cal.aBP以来的环境演化序列.对粒度、磁化率的变化及其反映的水文气候事件进行了解释.对于东部湿润地区的开放型湖泊而言,粒度仍然可以很好地反映气候干湿变化规律;而在河湖相交替沉积的地区,磁化率有两种赋存机制,在河流相沉积中其赋含在粗粒碎屑物质中,而当湖泊生产力相当旺盛的时候其与平均粒径呈负相关,但是与小于10 μm粒径呈显著正相关.全新世以来该地区经历了3次湖泊扩张时期,年龄分别为9 500～9 050、8 110～7 240、5 670～3 300 cal.aBP.另外,较为明显的河道前进事件有两次,分别发生在9 050～8 110和6 700～6 500 cal.aBP,此时湖泊严重收缩,河道占据原来的湖盆位置. The histories of hydrologic and climatic events in central Hebei Plain, for the past 11 640 cal. aBP are reflected by the fluvial-lacustrine sediments using proxy records of grain size and magnetic susceptibility. We propose a model that explains variations in grain size and magnetic susceptibility of fluvial-lacustrine sediments as a record of Holocene climatic and hydrologic changes. The model is based on the site around Lake Baiyangdian and incorporates the processes of erosion and deposit that are correlative with regional climatic events. For the open lakes in the humid climatic regions of eastern China, the grain size is still reliable for the reconstruction of environmental changes. But as for the fluvial-lacustrine sediments in this region, the magnetic susceptibility has two kinds of mechanisms. Namely, in the fluvial sediments the magnetic mineral was much richer in coarse materials especially in the matter bigger than 125 μm. But to the lakes with great productivity, it positively correlates with the content of fine materials less than 10 μm in grain size. In the Holoeene, this area has experienced three lake-spread episodes. The ages are 9 500-9 050, 8 110-7 240 and 5 670-3 300 cal. aBP respectively. Once more, there were two major fluvial aggradation events at 9 050-8 110 and 6 700-6 240 cal. aBP when the lake contracted and the river course occupied the location of the lake basin. Both the lake extent and the river progradation were driven by climate changes. When the climate was warm and humid, the lake spread. In reverse, the river proceeded.

关 键 词： 泥炭 河湖相沉积 粒度 磁化率 全新世 河北任丘

领　　域： [天文地球] [天文地球]