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.