Manasquan Formation

Manasquan Formation - Clay to clay-silt, massive to finely laminated, green to gray-green, extensively bioturbated. Calcareous microfossils are abundant in this unit. In the northwestern outcrop belt and shallow subsurface of the central sheet, the lower beds of the Manasquan Formation consist of a maximum of 10 m (33 ft) of fine- to coarse-grained, somewhat clayey, bluish-green glauconitic quartz sand. No calcareous macrofossils were found in this lithology. The sand minerals in the basal sand facies, excluding glauconite, consist of quartz, feldspar (10 to 25 percent), and siliceous rock fragments (a few percent). The glauconitic quartz sand is overlain to the southwest by a light- to dark-green, locally glauconitic, sandy clay-silt. This clay-silt is present at the base of the unit in the shallow subsurface. Eastward and in the intermediate subsurface, the Manasquan is primarily a clayey glauconite sand. In the deep subsurface, the Manasquan is primarily a massive to finely laminated, lightyellow clay-silt that has high concentrations of calcareous microfossils and has several hard indurated layers. In general, the formation thickens to the southeast where it is more than 60 m (197 ft) thick. The basal contact with the underlying Vincentown Formation is sharp and contains a thin zone, typically 0.61 m (2 ft) thick, of reworked glauconite sand, phosphatic debris, and sparse quartz granules. Gamma-ray logs through the Manasquan Formation have a large gamma spike along the basal contact. The age of the Manasquan was determined from calcareous nannofossils and, to a lesser degree, from foraminifera. The lower part of the Manasquan is assigned to the upper part of Zone NP 9 on the basis of the calcareous nannofossils Campylosphaera dela and Lophodolithus nascens and the absence of Zone NP 10 species. The upper part of the formation lies within Zone NP 13. This zone is characterized by the absence of Rhomboaster orthostylus and the presence of Discoaster lodoensis (Poore and Bybell, 1988). The foraminifera Planorotalites palmerae, which is present in this unit, has a range that correlates with the lower part of Zone NP 13 (Poore and Bybell, 1988).