Abstract The continental margin south of the Grand Banks (Fig. 1) is of transform origin and formed by shearing between the African and North American plates. It traces the northern limit of these plate motions. Its age is Early-Middle Jurassic in the northwest where it joins the rifted Nova Scotian margin and Early-Middle Cretaceous at its southeastern terminus. The northwestern segment of this margin (see geological map and Fig. 1) is similar to the adjacent rifted margin off Nova Scotia. The salt diapirs which form the Sedimentary Ridge Province continue northward from that rifted margin, and are present in the northwestern part of the transform margin. A thick sequence of Mesozoic-Cenozoic sediments are present in the South Whale Sub-basin, where stratigraphy and depositional environment is similar to that of the sediments on the Nova Scotia rifted margin. Thus, the junction between the Nova Scotian rifted margin and this transform margin is complex and diffuse. It is only southeast of the South Whale Sub-basin that the geologic style of margin typifies transform tectonics, and the transect crosses the margin in this region. Continental basement beneath the southern Grand Banks comprises rocks of the Meguma and Avalon terranes of the Appalachian Orogen (Hatcher and Williams, 1983). The detailed geology of these terranes is obscured by the overlying Mesozoic-Cenozoic sedimentary cover. Thus the Avalon zone is simply depicted as continental crust on this transect. The boundary between the Avalon and Meguma terranes is defined by the Collector Anomaly (Haworth, 1981), a positive gravity