Geological surveys of the East China Sea began in 1974.Since then

the Bureau of Marine Geology

Ministry of Geology and Mineral Resources is in charge of the extensive geological and geophysical investigations on this sea area of 770

000 sq km.Up to now

plenty of useful information have been obtained.According to seismic spectrum and well logging data

the stratigraphic sec-tions of the East China Sea can be divided in descending order as follows:the Donghai Group(Q)

the Shantan Formation(N

2

)

the Liulang Formation(N

1

3

)

the Yuquan Formation(N

1

2

)

the Longjing Formation(N

1

1

)

the Huagang Formation(E

3

)

the Pinghu Formation(E

2

)

the Paleocene and Upper Cre-taceous

etc.These sediments

which have a total thickness of 15

000m

consist predominantly of dark gray-greenish gray and light gray mudstones and sand-stones interbedded with conglomerates

carbonates and coal.The East China Sea includes following six tectonic elements(1st order):Zhemin uplift area

the East China Sea shelf basin

Diaoyudao uplift-foldedbelt

the East China Sea shelf foredeep

Okinawa trough basin and Ryukyu uplift-folded belt.The shelf basin can be divided into Fujiang

Zhedong

Taibei

Taixi depressions.The later three depressoins are subdivided into 14 sags(e.g.Xihu

Oujiang

Minjiang

Jilong)and arches(e.g.Hupijiao).Up to now

13 structural belts and more than 100 local structures(e.g.Longjing)have been located.The closed area of the local structure is generally more than 50 sq km

the largest one is up to 1

000 sq km.The East China Sea shelf basin

which has an area of 284

000 sq km

contains thick Meso-Cenozoic sediments

mostly deposited in marine

swamp and lacustrine environments

where there are abundant organic matters

many source rocks

shallower oil threshold depthes

good trap conditions and ade-quate timing.Commerial oil and gas have been tested from three horizons of Eocene

Oligocene and Miocene ages respectively in Pinghu and Longjing structures.The authors suggest that pressed anticlinal and buried-hill drapping anticlinal hydrocarbon pools are predominante in the basin

and other pools of stratigraphic

lithologic

reef and combination types could be also disco-vered there.