南四湖3000年来南北沉积差异

南四湖是华北地区最大的淡水湖泊，其形成演化与黄河泛滥、开挖运河、蓄水济运和泄洪保运等自然和人为的因素密切相关。本文对南四湖沉积物环境指标，如岩性、沉积速率、沉积物磁化率、总有机碳、总氮及碳氮比（C/N）和色素等进行了分析。结果表明0.62 ka BP前，南四湖南部微山湖和北部独山湖沉积物各环境指标同步变化，0.62 ka BP后，南四湖南北环境分异。3000年来该地区古环境变化经历下列过程：2.45 ka BP前有河流沉积环境的特点：色素指标为零，C/N比值高达60～80等；2.45 ka～1.3 ka BP，2.45 ka BP前后色素指标迅速上升，表明为还原环境，叶绿素及其衍生物、总类胡萝卜素保存较好C/N比值下降，内源有机质增加，频率磁化率升高，沉积的细颗粒成分增加，为南四湖形成发展时期；1.3 ka～0.62 ka BP，CDTC大幅度下降，而颤藻黄素、蓝藻叶黄素变化不大，藻类繁盛，表明这一时期水体较稳定；0.62 ka BP后，独山湖更多地接受入湖河流带来的碎屑物质，沉积速率加快，环境指标更具有河流环境的特点，而微山湖仍受黄泛影响，更具有湖相特点。上述南四湖南北沉积差异，将为分析研究南四湖的演化历史，确定该地区黄泛的影响程度和范围，为判别3000年来该地区人类活动的强度和对湖泊发展的影响提供依据。

SEDIMENTARY DIFFERENCE BETWEEN NORTH AND SOUTH NANSIHU LAKE，SHANDONG PROVINCE

Nansihu Lake, composed of Weishanhu Lake, Zhaoyanghu Lake, Nanyanghu Lake and Dushanhu Lake, is the largest lake in North China. In this paper some environmental indexes of sediments from Nansihu Lake, such as lithology, sedimentation rate, magnetic susceptibility, TOC (total organic carbon) , TN( total nitrogen), C/N and fossil pigment, were analyzed. The study shows that .sedimentary difference between north and south Nansihu Lake occurred at 0.62 ka BP. Before 2.45 ka BP, fossil pigment was not found in sediments, and C/N was obviously high and even reached 60 - 80, characteristic of fluvial facies. The period from 2.45 - 1.3 ka BP was the period of forming Nansihu, reflected by abrupt increase of pigment content, and corresponding change of other environmental indexes. Nansihu Lake was stable during 1.3 ka BP to 0.62 ka BP. After 0.62 ka BP, Dushanhu Lake in the north of Nansihu Lake was more like a river, while Weishanhu Lake in the south was a lake. Sedimentary characteristics showed above will be the basis of reconstructing the evolution history of Nansihu Lake, determining the level and scope of influence of the Yellow River flooding in this area and investigating the intensity of human activity in this area.