The Nanjemoy Formation belongs to two geologic groups; the Wilcox Group of the Gulf of Mexico Basin in the southernmost surface expression of the formation and the Pamunkey Group in the northern and central portions from Maryland in the north through Virginia and the Carolinas. Both geologic groups have been dated to the early Paleogene; the Paleocene and Eocene periods, or in the commonly used NALMA classification; Wasatchian, defined by the age-equivalent Wasatch Formation of Wyoming.
