鲁北平原浅埋古河道带基本特征

ELEMENTARY CHARACTERISTICS OF SHALLOW-BURIED PALEOCHANNELS IN LUBEI PLAN

鲁北平原大致分布有三条浅埋古河道带,呈西南一东北方向平行展布,每带一般宽5 -15km,最宽处达20km,沉积厚度在10-20m,最大40m,浅埋谷河道可分为两期,早期古何道形成于晚更新世晚期或全新世初期,晚期为全新世早一中期。古河道研究对本区经济开发,有着重要的理论意义和实r践意义。

The depth of shallow-buried paleochannels in Lubei(North Shan- dong Province)Plain are 8—60 meters underground.The paleochannels can be divided into three major paleochannel belts,which stretch par- allelly from southwest to northeast.They are generally 5—15kin wide, the widest section reaches 20km.Sediments of the paleochannels are mainly composed of fine sand,silt or medium sand,usually 10—20 me- ters thick,the thickest 40 meters.The floor levels of the shallow-bur- ied paleochannels consist of brown-yellow sandy clay or clay,the top levels grey sandy clay,clayey shad and mud. According to the characteristics of the paleochannel sedimental struc- ture and the synthetic analysis of granularity,mineral and spore- pollen data,the shallow-buried paleochannels can be divided into two sedimental stages.^(14)C dating shows that paleochannels in the first stage in the lower sedimental cycle was formed about 25000—9500 years B.P.They are,the river traces from the last period of the Late Pleis- tocene to the early period of the Holocene.The sediments in the sec- ond stage was formed 9500—4100 years B.P.,the early-middle period of the Holocene.