运用GPY浅地层剖面仪对太湖底质的探测

GPY型浅地层剖面仪是结合我国湖泊特点而研制的新型声学遥测仪器,可以迅速提供湖底地层空间展布概况。我们运用这一仪器,曾三次对太湖底质进行了探测,测线达200余公里,初步揭露了太湖是一个平均水深不到2m的浅水湖泊,湖底由坚硬的黄土物质所组成,其上覆盖着数厘米至数十厘米的现代沉积,黄土层之下为砂、泥互层的海相沉积,时代为晚更新世(距今约2.1—2.4万年),该沉层积之下则为棕色及灰色粘土层。这表明,在太湖形成之前这里曾是广泛覆盖着黄土的冲积平原环境,并非是由海湾和泻湖演变而来。黄土层之上,还发现有许多被淹埋的河道及小洼地。通过探测,也揭露了太湖沉积层中有许多埋藏的古潜山,表明它的基底并非是一个平坦的湖盆地地形。此外,还发现太湖底部地层中有浅层天然气分布,并且不断地沿着侵蚀沟谷向外逸出。 

SURVEY OF THE SUBSTRATE OF TAI—LAKE USING GPY ACOUSTIC METER

Acoustic meter of Model GPY is a new remote sensing tool which is developed with special regard to the characteristics of the lakes of China.It would quickly give a general idea about the spacial spreading of the strata under the lake.Using it for three times,we made a survey on the sub-strata of Tai-Lake,with the profile lines over 200km.Preliminary survey reveals that Tai-Lake is a shallow lake with average water depth less than 2m.The substrata,consisting of loessial material,is overlain with recent sediments of several to tens of centimeters in thickness,and underlain by marine sediment of sand and clay interbeds formed during late Pleistocene time(21000-21000 yrs ago).Under the marine sediments,there are brown and grey clays.All the evidences indicate that the alluvial plain extensively covered with loess was prevailing in that time.It was not resulted from a bay and lagoon environment.Over the loessial beds,many river courses and small sags are discovered.Furthermore,many ancient buried hills are also found,suggesting that the basement is not flat.Finally,it is found that shallow natural gas is distributed in near-surface beds of Tai-Lake,which is continuously escaping along errosion valley.