Hornerstown Formation

Hornerstown Formation - Sand, glauconite, clayey, extensively bioturbated, massive, medium-green in the shallow subsurface. Common to abundant microfauna in the subsurface are not present in outcrop. In the deep subsurface, the Hornerstown Formation consists of glauconite sand at base, overlain by a thin, laminated, dark-gray clay-silt that grades upward into a finegrained, clayey glauconite quartz sand. The formation is very thin and rarely exceeds 7.5 m (25 ft) in thickness. The basal contact with the underlying Kc4 cycle is difficult to place because both units are glauconitic sand; however, the basal Hornerstown contains dark-brown phosphatic debris. Less commonly the contact is marked by extensive burrows filled with glauconite sand that project downward into the underlying unit. Gamma logs from the Hornerstown have a very large gamma kick at the base of the formation. The age of the Hornerstown is early Paleocene (Danian) based on the presence of calcareous nannofossils (Chiasmolithus consuetus and Ellipsolithus macellus) and foraminifera characteristic of zones NP 3 and NP 4, and P1a to P1c (Chengjie Liu, Rutgers University, written commun., 1993), respectively.