212 
THE GEAND CASON DISTEIGT, 
sided as rapidly as they were formed. It was true of the Appalachians, of 
the Pacific coast, of western and central Europe, and I think the same is 
true of all the areas of great deposition throughout the West. 
When we reach the Cretaceous age we find that a little more light may 
be thrown upon the physical condition of the province, though much less 
than might be wished. So large are the areas where this series is the sur- 
face of the country, and so readily does the mind restore it to the places 
from which it has been denuded, that we feel almost as if we saw this great 
formation in its entirety. Wherever we turn in the Plateau Province the 
Cretaceous tells us the same story. All over its extent it is a lignitic and 
coal-bearing formation. We find coal or carbonaceous shales from the base 
of the series to the summit. Very abundant also are the remains of land 
plants in recognizable fossils, and these fossils occur not only in the carbon- 
aceous layers but in the sand-rock and marls as mere casts or impressions 
of wood and leaves. Intercalating with these are many calcareous la}mrs 
which yield marine mollusca in the lower and middle Cretaceous, and brack- 
ish water mollusca in the upper Cretaceous In a word, the parallelism, 
so far as physical and organic conditions are concerned, between the Creta- 
ceous of the Plateau Country and the Carboniferous coal measures of En- 
gland, Pennsylvania, and Nova Scotia, seems perfect. What the Carbon- 
iferous age was to the Appalachian region, such was the Cretaceous age to 
the great mountain region of the West. 
A careful scrutiny of the facts presented bj^ the Cretaceous strata of 
the Plateau Country brings up before us some very curious and perplexing 
problems. No one would hesitate to say that during the accumulation of 
these strata the surface of deposition must have been very nearly at mean 
sea-level. Yet the Cretaceous system varies from 3,500 to 8,000 feet in 
thickness in dilferent parts of the province. The continuous area which 
they covered south of the Uintas surely exceeds 100,000 square miles, in 
which not a single mountain chain, not a hill, not even a perceptible undu- 
lation of the strata is known to have then existed.* It seems at first very 
* There are some considerable areas of which we have but little knowledge, but we know the 
greater part of the province well enough to be sure that within the limits of observation the inference 
of the text holds rigorously. Very probably it holds good throughout the province. 
