Continuous seismic-reflection profiles across the Scotian shelf south of Cape Breton Island, Nova Scotia, reveal the presence of moderately folded Cretaceous rocks within the area represented by the Orpheus negative gravity anomaly. The folded strata are confined to the anomalous area, and contrast with the gently seaward-dipping strata typical of most other parts of the shelf.

Bedrock units are recognized on the continuous seismic-reflection records by unconformable relations and differences in definition, nature, and frequency of seismic events depicting layered sequences. A preliminary geologic map was constructed from these data, the adjacent land geology, and the gravity, magnetic, and seismic-reflection data obtained by other workers. Rocks in the anomaly area are thought to range in age from pre-Pennsylvanian to probable Tertiary.

The fold structures evident in the Cretaceous strata are attributed to movement along an eastward extension of the Cobequid-Chedabucto Triassic fault system that extends across Nova Scotia almost continuously from the Bay of Fundy to Chedabucto Bay. This system is postulated to extend eastward along the south side of the Orpheus anomaly, thence southeastward toward the continental slope. It may be part of a larger fracture zone continuing along the southwest margin of the Grand Banks and across the Atlantic Ocean.