Conclusions

The nearshore seismic stratigraphy revealed by our data complements the stratigraphic and geologic mapping previously completed in the vicinity of outer Cape Cod. The interpretations to the west of outer Cape Cod extend the Cape Cod Bay framework (Oldale and O'Hara, 1990) into the shallower nearshore areas of Cape Cod Bay and into Wellfleet Harbor. The stratigraphy east of Nauset Inlet coincides well with and expands the previous work of Aubrey and others (1982). The seismic profiles along the eastern nearshore of outer Cape Cod, north of Nauset Inlet, provide subsurface data for the first time.

The data show that fine-grained glaciolacustrine deposits are extensive in the nearshore subsurface off South Wellfleet and North Eastham, and may be extensive in the subsurface beneath the subaerial outwash in this area. The stratigraphic relationship between the glaciolacustrine unit and the glaciofluvial Eastham plain deposit that lies above is not clear. Our seismic profiles do not indicate the presence of extensive glaciolacustrine facies beneath the nearshore, north of Wellfleet.