鲁北平原黄河古河道初步研究

A PREFIMINARY STUDY OF THE YELLOW RIVER'S PALEO-CHANNELS IN NORTH SHANDONG PLAIN

鲁北平原黄河古河道可分为地面古河道(埋藏深度0—8m)和浅埋古河道(埋藏深度8—40m)。两类古河道部大致可分为三条古河道带,呈SW-NE向近平行展布,每带一般宽5—15km,最宽处可达20km。 古河道沉积层主要由细砂或粉砂组成,为古河床之曲流砂堤或天然堤沉积。各期古河道沉积层之顶、底板主要为粘土或亚粘土和淤泥层所构成,为古黄河泛滥相沉积物。 本区古河道按形成时间顺序可分为三期,下部第一期古河道大约形成于晚更新世晚期—全新世早期,中部第二期古河道形成于全新世早—中期,上部第三期古河道形成于全新世中—晚期。

According to buried deths, the yellow River's paleochannels can be divided into ground pal'eochaiinels (buried depth 0?m) and shallow-buried palecechannels (buried depth 8?50 m). They may all be routhly divided into three major paleochannel belts, stretching parallel with each other from -SW to NE in direction. The deposit layers of the paleochannel were mainly composed of fine sand, silt sand or medium sand partly; the floor level and top level of deposit layers of different stages are mainly made up of brown yellow sandy clay, clay and grey black sandy, clayeysand or clayey mud. ' On the basis of the characteristics of the paleochanriel's sedimental structures, other synthetic distinguishing features of the sediments and the I4C data, the paper suggests that the paleochannels in North Shandong Plain were formed in three stages: Paleochannels of the first stage (buried depth 50?5 m) formed in the last period of the late Pleistocene to the early period of Holocene; paleochannels of the second stage (buried depth 20? m) formed in early-middle period of Holocene; and the third stage (buried depth 8? m) formed in middle-late period of Holocene.