98 The American Geologist. August, looi 
ness of a shore line for the Jamcsburg sea. The material mak- 
ing up the Jamesburg formation is very much hke that going 
to make up the Pcnsauken. Professor Sahsbury states : "In 
some places the weathering of the latter (Pensauken) might 
have given rise to the overlying bed, which is here classed as 
Jamesburg." He states that there is in the Jamesburg an ab- 
sence of the materials which in the Pensauken are decomposed, 
such as granites, gneisses and schists, as well as the Triassic 
shales and sandstones, which are commonly found in the Pen- 
sauken. The age of the Pensauken is made equivalent to that 
of the Columbia or a part of it, for he said : "The Jamesburg 
is, therefore, but a local name for the Columbia formation, or 
for a part of it." It is correlated with an early glacial epoch, 
and Trenton and Trenton Junction are given as excellent locali- 
ties for the Jamesburg. 
In his report for 1894, professor Salisbury regards the 
Jamesburg as a mantle, covering the country up to^ 214 feet 
or more. He considers it corresponding in a general way to 
the high-level and low-level Columbia, but that the Columbia 
of the sdfuth is believed to include more than the Jamesburg of 
New Jersey. The Jamesburg not only covers the bottom, but 
is found lapping up on the sides of the trough between Raritan 
bay and the Delaware river with a distribution as wide as that 
of the Pensauken. It is unconformable on the latter and on 
older formations. Near Cream Ridge, the Jamesburg is stated 
as occurring at 214 feet and near Marlton 180 feet. 
The Jamesburg is now divided into high-level and low-level 
Jamesburg. The relations of the high-level Jamesburg are 
very obscure, the low-level Jamesburg seems somewhat easier 
to recognize. In regard to the high-level Jamesburg, profes- 
sor Salisbury says : "The high-level Jamesburg is often very 
thin. Where it rests on the Pensauken it frequently has the ap- 
pearance of being but the weathered part of the latter, so that 
it is often very difiicult to distinguish between them on litho- 
logical grounds. So true is this that study had been long in 
progress before the existence of the 'high-level' Jamesburg 
over the higher areas of the Pensauken was regarded as dem- 
onstrated. The great body of facts now in possession, how- 
ever, has put the existence of this phase of the formation be- 
yond (juestion. This statement is made with full recognition of 
