236 CEMENT MATERIALS AND INDUSTRY. [bull. 24; 
TRENTON LIMESTONE. 
Above the magnesian Kittatinny limestone and resting 1 on it is 
dark-blue or black fossiliferous limestone. In the early reports of thi 
New Jersey geological survey it is called the -'fossiliferous" linn 
stone, in distinction from the Magnesian or Kittatinny limestone, i 
which fossils had not been found at that time. In age it is to be corn 
lated with the basal portion of the Trenton series of New York. 
A continuous section of this formation is nowhere exposed, but i 
general the succession of beds is about as follows: 
Section of black fossiliferous limestone of 'New Jersey. 
(a) Black calcareous shales or earthy limestone, gradually becoming less cal- 
careous and more siliceous or clayey and grading into the overlying 
slate. Thickness is apparently variable 
(b) A rough, irregularly bedded, dark-blue limestone, breaking into knotty 
slabs 
(c) Probably calcareous shale, usually not exposed 
(d) Blue-black, earthy limestone, rather evenly bedded, weathering to a light 
blue gray - 
In Sussex Count/y the total thickness is uniformly about 135 to li 
feet, except where faults have probably repeated some layers. Tl 
formation, however, thickens to the southwest, being probably at lea 
300 feet at the Delaware, and possibly even more than this in tl < 
Lehigh Valley region, Pennsylvania. The increase in thickness 
apparently in the upper calcareous shaty beds. 
The Trenton rests upon the eroded surface of the Kittatinny lim 
stone, so that there is here a break in the geologic record. At mai| 
places the lowest Trenton beds form a conglomerate composed solej 
of pebbles and bowlders of the underlying magnesian limestone auf 
chert. Elsewhere pebbles of magnesian limestone and chert a 
included in a matrix of pure limestone, which is sometimes fossiliferon 
Many anatyses have been made of specimens both of the limesto 
and of the calcareous shales of the Trenton formation. The mot 
massive beds contain from 85 to 95 per cent of carbonate of lime an 
only small amounts of magnesia. Some of the more shaly la}^ers co< 
tain 65 to 75 per cent of carbonate of lime, with sufficient alumina a 
silica to make a good cement rock. It is this rock which is used wi 
such success in manufacturing Portland cement near Phillipsbuii 
Warren County, N. J., and in Berks, Lehigh, and Northampt 
counties, Pa. The purer limestone beds can be used to mix with t 
"cement rock" in order to raise the percentage of lime to the nec< 
sary figure. 
