214 
THE GEAND OASTON DISTEICT. 
winds — would persist as far as the depths remained shallow. Some such 
explanation as this, if it be tenable, would greatly assist us in explaining 
the wide diffusion of cross-bedding displayed in the Jura-Trias. It is 
generally accepted as an explanation for ripple mai’ks that they are formed 
in shallow and moving water, and ripple marks are almost as abundant here 
as cross-bedding. 
It would be extremely interesting to know what was the relative distri- 
bution of land and water over the western part of our continent in the 
closing periods of the Cretaceous. In a general way we know that the 
greater portion of the West was submerged. We also know that consider- 
able land areas existed there. Sometimes we can point with confidence to 
a particular area and assert that it was land in Cretaceous time, but as a 
rule we are in doubt about the land areas. The largest piece of terra firma 
which is known was the Great Basin area, and even here we are unable to 
fix more than a small part of its shore line. We are reasonably confident 
that some and perhaps most of the great mountain platforms of the eastern 
ranges were above the waters with submerged valleys between them. We 
also know, and the fact is a momentous one, that nearly the whole of the 
vast region of the West corresponded in its physical condition to what we 
have inferred for the Cretaceous age of the Plateau Country. But detailed 
knowledge of the geography of the land areas in that age is exceedingly 
meager. Perhaps, however, we may make some very general statements 
which are not without value. 
We cannot as yet affirm confidently that the Cretaceous ocean stretched 
from the lower Mississippi to the Pacific Ocean; but the facts now known 
indicate that if the two oceans were separated in that age the separation 
was only by a very narrow land area. We can travel from the Mississippi 
to the Pacific, between the thirty-fourth and thirty-seventh parallels, without 
being at any time more than fifty miles distant from some known mass of 
Cretaceous beds. If some gaps in existing knowledge could be filled up, 
we might be able to close up the vacant spaces in the distribution of the 
Cretaceous, and say that strata of that age once stretched continuously 
between the termini just mentioned. Indeed the only gap of importance 
is in the extreme southern part of Nevada and southern California. Every 
