Geologic units in Dukes county, Massachusetts

Cretaceous sediments (Cretaceous) at surface, covers 89 % of this area

Clay, silt, sand, and gravel, mostly of non-marine and nearshore marine origin, Campanian and older.

Granite, gneiss, and schist, undivided (Proterozoic Z) at surface, covers 11 % of this area

Plutonic and metamorphic rocks of probable Proterozoic Z age. May include plutonic and volcanic rocks of Paleozoic or younger age.