晚更新世以来潍河古河道沉积及其对现代咸水入侵的控制

Sedimentary Characteristics of Weihe Palaeochannel Since Late Pleistocene and Their Control to Modern Salt-Water Intrusion

在莱州湾潍河古河道沉积区选取 4条典型地质剖面 ,对典型钻孔岩芯进行粒度、14 C及热释光测年分析 ,结合野外实地考察及 10 0余个地质钻孔资料的分析 ,揭示了潍河晚更新世以来古河道的沉积特征。沉积剖面自下而上沉积物粒度逐渐减小 ,潍河以东古河道砂层厚 30～ 5 0m ,连续性好 ;潍河以西古河道砂层厚度小于 2 0m ,连续性较差。沉积特征的不同导致潍河以东地区咸水入侵发生早 ,后期变缓 ,为上淡下咸二层水文地质体 ;潍河以西地区咸水入侵主要是 2 0世纪 70年代末期以来在人类活动的干预下大规模的入侵 ,沿古河道入侵距离可达 9～ 10km ,为淡 -咸 -淡三层水文地质体。研究古河道沉积与咸水入侵的关系 。

The lower reach of Weihe River in the south plain of Laizhou Bay is one of the most typical areas of salt-water intrusion in China. The occurrence, development and movement pattern of the salt-water intrusion are closely related to the sediments composition in the palaeochannel of the Weihe River. A detailed investigation including data collected from more than 100 geologic drillings, analyses of sediment grains and microfossils, 14C and thermoluminescence age data from two typical bores has been conducted to study the distribution and sedimentary characters of the palaeochannel since the Late Pleistocene. The relationship between sedimentary structures and burial characters of palaeochannel and salt-water intrusion are then discussed. The results of this study have suggested that the sediments in the paleochannel can be divided into 4 sedimentary cycles according to grain size. The calculated depth of sand sediment indicates that the thickness of sand layer is about 30 to 50m in the eastern part but less than 20 m in western part of Weihe River, and the continuity of sand layer is also better in the eastern part than in the western part. The difference of sedimentary characteristics lead to the salt-water intrusion earlier in eastern part and became slow recently, while the salt-water intrusion in western part occurred since late 1970's mainly due to the human exploitation of groundwater and the intrusion distance of salt-water through the paleochannel can reach to 9 or 10 km. The study of paleochannel sediments and its relation to salt-water intrusion can provide scientific reference to ground water exploration and the control measures of salt-water intrusion.