Hutt—On the Geological Age of the North Atlantic Ocean. 315 
replacement by limestones, shows that this region was submerged and remote from 
land.* 
(d) Upper Carboniferous.—The evidence derived from the distribution of the 
Upper Carboniferous strata tallies in the main with that from the lower division. 
The sedimentary strata increase in thickness towards the east or north-east, and thin 
out, or pass into limestone, in a westward direction, extending as far as the Rocky 
Mountains. Thus, in Pennsylvania the Upper Carboniferous beds reach a thickness 
of 3000 feet; in Western Kentucky 3300 feet In Kansas, according to Mr. 
Broadhurst, the representative beds consist chiefly of limestone; while in Nevada 
they are represented by 2000 feet of limestone above the Weber Quartzite. In 
Missouri and Iowa, the strata (chiefly sediments) are only 600-1000 feet in thick- 
ness; and in Michigan they have thinned down to 123 feet. The great formation 
of Carboniferous limestone of the Rocky Mountains, described by Dr. Hector, pro- 
bably represents an oceanic deposit of organic origin, representing the entire Carbon- 
iferous series of north-eastern America. 
Combining the evidence from both the upper and lower divisions, we find the 
following suggestive results. If we take a section, drawn from New Brunswick 
on the extreme N. E., through Pennsylvania, Missouri, into Utah on the 8. W., 
we shall find the following changes in the characters and thicknesses of the Car- 
boniferous strata :— 
Comparative Carboniferous Sections of America. 
S.W. Utah. Missouri and Iowa. Pennsylvania. N.E. New Brunswick. 
Upper Carbs. Limestone 600-1000 ft. (sediments), 8000 ft. (sediments), 14.570 (sediments 
Do. i 
Lower Carbs. only. 1000 ft. (limestone), . 5000,, mainly). 
Total of Sediments, . 600-1000 ft. 8000 ft. 14,570 
The inference of an Atlantic continent in Carboniferous times, to be drawn 
from a consideration of the distribution of the Carboniferous strata, has been 
recognised by several geologists. Lyell dwelt upon this subject many years ago, 
even at a time when much of the evidence in its favour, now available, had not 
been obtained.t The more recent researches of American geologists in the regions 
lying to the south and west of the United States of America go to confirm the 
* In the Nevada territories (40th parallel) the Lower Carboniferous limestone attains a thickness 
of 7000 feet, according to Mr. Clarence King, and is succeeded by the Weber quartzites, or sandstone, 
6000 feet, occupying the position of the “‘ Millstone Grit;”’ and this again by the Upper Carboniferous 
limestone, 2000 feet.—‘‘ U. 8. Exploration of the 40th parallel,’ vol. i. The Weber quartzite is a local 
formation, originated during the temporary elevation of that region between the upper and lower 
oceanic epochs, represented by limestone. 
+ ‘Principles of Geology,” 10th edit., vol. i. p. 256, &e. 
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