40 NEW YORK STATE MUSEUM 
was completely submerged under the Ordovicic sea except for the 
Adirondack island and alternating land and water conditions im- 
mediately around that island. 
Without going into the details of the formations, it is important 
to mote that the earlier Ordovicic deposits were almost wholly lime- 
stones, while the later deposits were nearly all shales and sand- 
stones. Thus in southeastern New York the thick Wappinger lime- 
stone is overlaim by the still thicker Hudson River shales and sand- 
stones. In northern New York we have the Beekmantown, Chazy, 
Black River, and Trenton limestones overlain by the Trenton 
(Canajoharie), Utica, and Frankfort shales and sandstones. It 
should not be understood, however, that all the formations named 
are present in unbroken succession, because the oscillations of level 
(above mentioned) occasioned certain interruptions in sedimentation. 
The predominance of limestone formation in the earlier Ordovicic . 
sea of New York proves that the waters of that time were com- 
paratively free from land-derived sediments and this,,in turn, is 
best accounted for not by great depth of water and distance from 
land, but rather by the fact that all the nearest land areas were 
comparatively low and small, and hence were not undergoing very 
active erosion. During the later Ordovicic the adjacent lands were 
considerably higher and no doubt larger, so that vigorous erosion 
resulted and muds and sands were largely washed into the sea. 
The aggregate thickness of Ordovicic strata in New York is be- 
_tween 2000 and 3000 feet. It should not be inferred from this fact 
that the Ordovicic sea was ever two or three thousand feet deep. 
Even the limestones abundantly show by ripple marks, mud cracks, 
fossils etc. that they were laid down in shallow sea water. The very 
character of the materials (old muds and sands) in the Upper 
Ordovicic formations shows that they could not have been deposited 
in deep ocean water. Such sediments are not now forming on the 
deep sea bottom. But how are these statements to be harmonized 
with the fact that nearly 3000 feet of Ordovicic strata exist in 
New York? During the whole period (with certain exceptions 
above noted) the land gradually subsided and in this slow down- 
ward movement stratum after stratum was formed upon the sinking 
sea-floor, so that at no time is it mecessary to assume great depth 
of water. In general, the Ordovicic sea of North America must 
be thought of as a vast shallow (continental) sea which spread 
over most of the slowly subsiding continent. There were no ocean 
abysses at all comparable to those of the present ocean. 
