THE GEOLOGICAL HISTORY OF NEW YORK STATE 31 
DISTRIBUTION, THICKNESS AND AGE OF THE GRENVILLE 
The Grenville is associated with rocks of younger age in the 
Adirondack region, so that the formation is not present as a single, 
continuous mass of surface rock covering the whole area. It is, 
however, so abundant and widespread in great and small areas 
throughout the Adirondack province that we may confidently assert 
that this whole district was under water during Grenville time. As 
the geologic structure strongly suggests and as certain deep wells 
prove, rocks of this age must extend, under cover of the later 
Paleozoic sediments, for a considerable distance beyond the Adiron- 
dack area. Precambric rocks have long been recognized in the 
Highlands district of the lower Hudson and recent work makes it 
practically certain that strata of Grenville age exist there. Pre- 
cambric (doubtless including Grenville) occurs along the western 
border of New England and it should also be mentioned that Gren- 
ville strata are extensive over much of southeastern Canada. Pres- 
ence of Grenville strata in southwestern New York is somewhat 
doubtful because, if there, they are effectually concealed under the 
heavy cover of Paleozoic strata. The positive existence of Gren- 
ville, however, just to the north in Canada and in northern and 
southeastern New York, makes it more than likely that the Gren- 
ville underlies the Paleozoic rocks of western New York also. Such 
a widespread distribution of the Grenville sediments shows that 
deposition went on in a very large body of water; large enough, in 
fact, to be called an ocean. Thus, bearing in mind all the facts, we 
are led to the important conclusion that, during Grenville time, all 
of northern and eastern and probably southwestern New York was 
under the sea. In other words, the most ancient known geographic 
condition nm New York was a great expanse of ocean water cover- 
ing most, if not all, of the State. 
As the rocks are badly disturbed and folded, and as the top or 
bottom of the formation has never been recognized as such, it 1s 
impossible to give anything like an exact figure for the thickness of 
the Grenville rocks. Continuous successions of strata. have been 
observed in enough places, however, to make it certain that Gren- 
ville strata were piled, one layer upon another, to a thickness of 
many thousands of feet. This clearly implies that the Grenville 
ocean existed for a vast length of time which must ibe measured 
by no less than a few million years, because in the light of all our 
knowledge regarding the rate of deposition of sediments, such a 
very long time was necessary for the accumulation of so thick a 
mass of rocks. It does not necessarily follow that the Grenville 
