April, 1911.] 
The Ancient Vegetation of Ohio. 
3W 
underlying the coal seams is intimately connected with a long- 
continued growth, sudden submergence, and subsequent fossiliza- 
tion of marshes adjacent to an ancient sea, and of great inland 
xerophytic vegetation formed in island-like masses very much like 
the peat bogs of today, but over much wider areas than any single 
present day bog occupies. The Carboniferous system includes 
the Potts ville, Allegheny, Conemaugh, Monangahela and Dunkard 
formations, all of which have been described in great detail in the 
later volumes of the Geological Survey. Over these rocks of at 
least two-thirds of Ohio are spread in varying thickness the 
deposits of the glacial drift. The glacial formations of Ohio have 
been very fully described by Leverett (12) ; a brief account follows 
in another paper in connection with the present distribution of 
vegetation in Ohio lakes and peat deposits and the physiography 
of the state. 
The mode of arrangement of all geological formations is that of 
sheets resting one upon another, but not horizontally. Slow and 
comparatively gentle movements of the earth’s crust, unaccom- 
panied by fractures or displacements have given rise in the state 
to a system of northeast and southwest foldings. The most 
important of these is, as has been stated at the outset, the Cin- 
cinnati axis which traverses the state as an arch from Cincinnati 
to the lake shore and beyond into Canada. The other lines of 
elevation are relatively weak and come into Ohio from Pennsyl- 
vania and West Virginia, and are known respectively as the 
Appalachian fold, the Fredericktown and Salisbury anticlines, and 
the Wellsburg, Cadiz, and Cambridge anticlines, located near 
places of that name. They are undoubtedly folds of the great 
series to which the Allegheny mountains of Pennsylvania and 
West Virginia belong. This emergence of the rocks of the state 
has its approximate date at the close of the Lower Silurian period, 
and has never been more than a low mountain chain. 
Along a large part of the Cincinnati axis the strata which once 
arched over it have been extensively worn away. They are found 
resting in regular order on either side. The geological map of 
Ohio recently published shows the areas covered by the principal 
systems and their series of strata. In the region about Cincinnati 
the erosion has been greatest, exposing there the oldest rocks. 
The direction of the draining streams of the western half of the 
state has been mainly determined by this great anticlinal axis. 
It forms the divide between the waters of the Scioto and the 
Miami, and between the Sandusky and the Maumee. On the 
east side of the anticlinal axis the rocks dip down into a basin in 
which all the strata form trough-like layers, their edges outcrop- 
ping eastward on the flanks of the Allegheny mountains. The 
older rocks are deeply buried, and the surface is here underlaid 
by the highest and most recent of rock formations, the Coal- 
