a ee ess SS ae eee, EL eee eee ey eae ae pe aa Te eS ee est pe ree es 
Sh adil cal ail 
bh 
aie 
ease ae 
ial 
aS ae 
ae 
ae 
a 
. 
3 
W. M. Fontaine—Mesozore Strata of Virginia. 31 
this northern Azoic belt, the agent which produced such 
extensive general denudation found, it is true, the Azoic deeply 
decomposed, and having its surface in the condition now found 
in the southern and southwestern part of the State, but it swept 
off all this loose granitic matter, and even reached the sound 
rock in many places. e€ may now turn to the consideration 
_ of some of the special features shown in the different belts. 
The New Jersey Belt.—Ot this I shall have little to say, except 
to call attention to certain remarkable deposits of stones on its 
_ western margin. The deposits of similar matter in the north- 
ern exposures of this belt are called conglomerates, and some- 
times breccias. For the beds in Virginia these terms are inad- 
equate. They are rather beds of bowlders. The northwest dip 
of the Mesozoic beds with which they are associated, and their 
position on the western side of the belt, show that if these de- 
posits are contemporaneous with the other Mesozoic strata, they 
are the last formed. But in some cases at least it is not clear 
that the period of their deposition followed immediately that of 
the typical Mesozoic beds. These stones are found in uncon- 
associated. These latter consist of sandstones and shales, well 
sorted and bedded by water action, and with their mineral con- 
stituents too much decomposed to betray, except in rare cases, 
the parent rocks. The case is different with the stones in ques- 
tion. They are of such large size, and the material is so fresh, 
that there is no difficulty in determining the precise character 
of the rock from which they were derived. Indeed the material 
1s often as sound as if it had been taken from a quarry ame 
or less argillaceous matrix, derived either from the erosion of 
the normal Mesozoic beds with which they are associated, or 
rom comminution of their own substance. These deposits are 
often sharply distinct from the associated normal Mesozoic beds, 
and appear as if deposited in depressions in them anenveiet Oe 
erosion. But again they appear sometimes alternating wi 
shales, and thus to form strata contemporaneous with the nor- 
