April, 1911.] The Ancient Vegetation of Ohio. • 319 



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 S3'stem includes 

 the Pottsville, Allegheny, Conemaugh, Monangahela and Dankard 

 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 var^dng 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 cither 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 

 Aliami, 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- 



