Shallow seismic (sparker), magnetic and bathymetric profiling were carried out on two cruises in the outer Oslofjord in 1979 and 1980.
The survey area is characterized by deep silled basins defined by the main structural trends of the surrounding land area. The Quaternary sediments, largely restricted to these major basins can be divided into three main units of supposed pre-Weichselian to Holocene age. Most of the sediments were
probably deposited during relatively short time intervals in the Late Weichselian under ice-proximal conditions, and in the early Holocene.
Magnetic total field and scismic data were uscd to map the submarine outlines of the Permo-Carboniferous Vestfold lavas, the Permian sedimentary rocks and the Larvikite body. The presence of other intrusives in the eastern and southern part of the survey area is discussed.