Twelve generalized structural contour maps were prepared from a study of 169 well
logs or sample logs of drill cuttings from the Coastal Plain of New Jersey, Delaware, and
the E astern Shore of Maryland. The configuration of the tops of the nonmarine Cretaceous
deposits (Patuxent , Patapsco, Raritan, and Magothy formations) and the Piney Point Formation
(Eocene) show the known subsurface extent of these formations in both New Jersey
and Delaware. The structural contour maps show the tops of the Merchantville Formation
and Woodbury Clay, the Englishtown Formation, the Marshalltown Formation, the Wenonah
Formation and Mount Laurel Sand, the Navesink Forma ti on, and the Red Bank
Sand which are a ll of Late Cretaceous age. The maps of the Hornerstown Sand, the Vincentown
Formation, and the Manasquan Formation and Shark River Marl of early Tertiary
age show the subsurface extent of these formations only in New Jersey. Also included is an
outline map showing the locations of wells and seismic station s and a structural contour map
showing the configuration of the bedrock surface of the report area.
Structural contours on top of the Magothy Formation, or on the top of the Raritan Formation
where the Magothy formation is absent, show the configuration of the nonmarine
deposits of Cretaceous age. Isopachs of the nonmarine deposits are derived by interpolation
between contours on top of the bedrock and the top of either the Magothy Formation or the
Raritan Formation where the Magothy is absent.
The Merchantville Formation and Woodbury Clay are difficult to separate in the subsurface,
and therefore the contour a re drawn on top of the Woodbury Clay. In New Jersey,
the thickness of the combined Merchantville Form a ti on and Woodbury Clay ranges from
ab out 100 to 140 feet near the outcrop, but exceeds 250 feet in the subsurface along the
coast in Ocean County.
The top of the Englishtown Formation is easy to recognize because it generally consists
of a micaceous white and yellow sand, although locally it is a silty clay . The formation
thins toward the southwest from about 160 feet in central Ocean County to less than 20 feet
in Salem County . It has not been recognized in Delaware.
The Marshalltown Formation varies from black clay to a glauconitic sand. It usually
ranges in thickness from 20 to 60 feet . It is very thin or absent in Delaware.
The Wenonah Formation and Mount Laurel and arc difficult to separate in New Jersey,
and therefore are shown as a unit. The combined thickness range from 60 to 100) feet. In
Delaware the two formations are easily separated.
The Navesink Formation is generally highly glauconitc and it is difficult to determine
the upper limit where overlain by the Hornerstown Sand which is also glauconitic. The contour
map on the top of the Navesink is based upon relatively little control.
The Red Bank Sand reaches a thickness of about 160 feet in Monmouth County. It thins
southwestward and is absent in outcrop in the southern part of the Coastal Plain of New
Jersey. A probable equivalent of the Reel Bank has be recognized in Delaware. The Tinton
Sand Member is the topmost unit of the Red Bank and in Monmouth County.
The Hornerstown Sand is most glauconitic and is about 30 feet thick in outcrop. This
is overlain by the Vincentown Formation which consists of two facies (1) calcareous sand
facies and (2) quartz sand facies. These a re overlain by the Manasquan Formation and
Shark River Marl which are here treated as a unit . In outcrop the combined thickness of the
Manasquan Formation and Shark River Marl is about 40 feet, but in the subsurface they
thicken to about 200 feet. The Piney Point Formation of Jackson age occur in the subsurface
in Cape May and Atlantic Counties, N.J. and in southern Delaware but is not
exposed in these States.
Brief notes are given on formation of later Tertiary and Pleistocene age , but no contour
maps were constructed.
Additional publication details
State/Local Government Series
Generalized structure contour maps of the New Jersey coastal plain
Geologic report (New Jersey)
New Jersey Deptartment of Conservation and Economic Development