Time sections from over 1000 line miles of land and marine seismic reflection surveys carried out by Geoseismic (Aust.), Western Geophysical Co., Namco International, and the South Australian Mines Department, are subdivided into superimposed groups of reflections on the basis of discordance or persistent reflectors. These reflector groups correspond to the major subsurface stratigraphic units determined from the six deeper oil exploration wells. Consequently, the subdivided time sections may be regarded as generalised geological sections from which the broader aspects of the structure and sedimentary distribution in the Gambier Embayment are determined. The major structural units recognised are, from north to south: Padthaway Ridge, Robe-Penola Trough, the Kalangadoo-Beachport basement High, and the Mount Salt Syncline which straddles the present coast south of Beachport. The first-mentioned three structures are the products of differential block faulting during the Late Jurassic and Early Cretaceous, but the Mount Salt Syncline appears to be a composite feature which resulted from broad downwarping along a ?late Lower Cretaceous hingeline to the north, complemented by late Upper Cretaceous uplift to the south. The axis of this syncline appears to intersect the older structures in the offshore area north-west of Beachport, but the southern flank, although slightly discordant with the adjacent continental margin, is probably associated with the formation of this feature.