Atlantic Highlands Cretacic — Prather. 165 
portant and characteristic member of the New Jersey Cre- 
tacic. 
Both Cook and Clark have included a part of the upper 
Navesink with the Redbank, but the lithological character 
of the material of the two formations is so different (one 
being a quartz sand and the other a clay or glauconite bed) 
that the line of separation can be traced without much 
difficulty. The material of these beds was undoubtedly de- 
rived from the older rocks to the southeast, as already sug- 
gested by Cook.* Clark gives the strike North 50 East 
with a dip of 25 feet to the mile. 
The Navesink Marl. 
This was named by Clark from its typical development 
in the vicinity of the "Highlands of Navesink," Monmouth 
county, New Jersey. He gives its thickness as 30 to 50 feet 
with the same dip and strike as the Redbank. This is one 
of the most important divisions of the New Jersey beds, 
and besides yielding 300-400 species of invertebrates, it con- 
tains more glauconite on the whole than is found in any 
other of the divisions. It is well exposed at Atlantic High- 
lands where it varies from 10 to 50 feet in thickness. It 
is generally of a dark green to light grey color while some 
layers are so dark as to be called black. These dark layers 
may be due to a certain amount of vegetable matter mixed 
with the glauconite. The light grey color comes from 
weathering and may partly be due to the decomposition of 
the pyrite contained in the bed. The dark layer which is 
generally about 10 feet thick may even assume a blue color. 
There are three distinct fossil beds in the Navesink 
which I have called bed 1, bed 2, and bed 3, beginning at the 
top. The fossils in bed 1 (which is characterized by Exo- 
gyra costata and Ostrea larva are replaced by limonite 
which, being characteristic, separates these fossils from 
those of the other two beds. Bed 2 is the Gryphcea vesicu- 
aris bed which also contains Bellemnitella americana, Os- 
trea larva, Exogyra costata, and Terrabratella plicata. The 
fossils in this bed have the parts of the original shells while 
those of the other beds are chiefly internal molds. There is 
much clay mixed with the glauconite and the formation on 
* Geology of New Jersey, 1868. 
