200 
IOWA ACADEMY OP SCIENCES. 
Aughey* argues that the Lower Coal Measure beds might be 
reached at any locality between Omaha and Plattsmouth at 
from 800 to 900 feet from the surface. This is exceeded some- 
what by the figures here given; and is at the same time consid- 
erably more than the theoretical estimates of the earlier 
writers. 
As to the general lithological character of the Upper Carbon- 
iferous beds in the area under discussion it may be said that 
there is a difference in the several sections so far as the asso- 
ciation is concerned, but similar beds may be traced over the 
entire region. 
It is a npticeable feature that while the upper or exposed 
strata are prevailingly limestones, in the case of under layers 
as shown by borings, the reverse is true, they being made up 
of argillaceous shales interlaid sparingly with ledges of lime- 
stone, bituminous shales, coals and sandstones. The total 
depth, however, of the exposed strata is by no means compar- 
able with that of the concealed beds. These upper limestones 
may have occupied at the close of the Carboniferous epoch the 
highest position of that formation, or may have been overlain 
by softer strata such as clay shales or even arenaceous depos- 
its, which being comparatively friable easily gave way to the 
later erosive agencies. The limestones as well as many of the 
shales are highly fossiliferous. The bituminous veins, whether 
coal or shale, are rather uncommon in occurrence and the indi- 
vidual layers rarely exceed two feet. The coal seam mined in 
Adams, Taylor, Page, Montgomery and Adair has an average 
thickness of perhaps twenty-one inches with an extreme of 
thirty inches. As yet the existence of heavier veins has not 
been definitely proven; the certain detection of coal beds of the 
Lower Coal Measures has not been possible and no satisfactory 
evidence indicating the presence of such seams as are mined in 
central and southeastern Iowa and in Missouri has been pro- 
duced. 
The Nodaway coal underlies a large territory, perhaps a 
greater one than that of any other vein in the state; it has been 
safely traced from the southern edge of Cass county as far 
south as the state boundary and northward from this line for 
somemiles. It is even possible that the Adair county coal as 
well as the vein found in western Mills county and running 
across into Missouri may be connected with the Nodaway seam. 
* Phys. Geog. and Geol. of Neb., p. 66. 1880. 
