(47) 
below the Sassafras river; on the western shore in Anne 
Arundel county the areal distribution is variable on account 
of the broken character of the country, but is on the whole 
narrower; further south, in Prince George county, it forms 
but a narrow strip less than a mile in width. 
The materials are variable; sands and clays predominate. 
The sands are sometimes white and coarse, but more com- 
monly fine-grained and colored by iron, even causing local 
induration, or they may be mixed with argillaceous materials 
forming silvery micaceous sand, or chocolate-colored marl, 
glauconite grains being present in greater or less amounts. 
The clays are generally black or drab, locally carrying seams 
and pockets of glauconite; occasionally they are calcareous 
as a result of their molluscan contents. 
The thickness is variable, but becomes reduced to the 
southward. It increases considerably to the southeast, judg- 
ing from the well records.* In northern Burlington count 
the Matawan is less than 200 feet thick; east of Philadelphia 
and Camden it is 125 feet; in Gloucester county it is 175 feet 
in places; in Salem county it is 80 feet; in Delaware not 
over 60 feet; near the mouth of the Sassafras river in Mary- 
land it is 100 feet; in eastern Anne Arundel county it is 60 
feet; in western Anne Arundel county and Prince George 
county it is thinner, until at Fort Washington bluffs it is a 
little more than 15 feet. Its farthest known southern appear- 
ance is in the valley of Piscataway creek; on the opposite 
shore of the Potomac the Eocene rests directly on the Poto- 
mac formation. 
Long thought to conformably overlie the Raritan, an un- 
conformity is now known to exist, although the time interval 
was not very great. Along Raritan Bay in the vicinity of 
Cheesequake creek where the upper Raritan contains dark- 
colored clays, the interbedded sands and clays gradually 
grade from Raritan into the Matawan. Further inland and 
to the southward the interval was greater since the Matawan 
gradually transgresses the Raritan and comes to rest, in cen- 
* Woolman, Ann. Rep. State Geol. N. J. 1895 . 63-95. 1896. 
