I. INTRODUCTION 
Dynamic plant geography or physiographic ecology, is intimately 
related to topography and to soil, and consequently, to physiographic 
history and to geologic formations. It is therefore necessary to know the 
essential features of the geologic and physiographic history of a region 
before its plant associations can be understood. 
In this paper, the area considered is that generally known as the Cin¬ 
cinnati region. It includes, in Ohio, Hamilton and Clermont counties, 
and the southern parts of Butler and Warren counties; in Kentucky, the 
northern parts of Boone, Kenton, and Campbell counties (see map, fig. 
59)- 
Considerable has been published on the geology and on the topo¬ 
graphy of the Cincinnati region; and a recent contribution by Fuller and 
Clapp (1912) gives a brief treatment of both the geology and topography, 
preliminary to a discussion of the underground waters. But believing 
that the reader of plant geography does not wish to search geological lit¬ 
erature, especially when it is as scattered as it here is, a brief summary 
of the features most essential to the ecologist is here given. 
The flat hill-tops or uplands are but remnants of the Tertiary pene¬ 
plain, uplifted and partially dissected. Near Cincinnati, these uplands arc 
merely flat-topped divides, a half mile or a mile in width, for near the 
Ohio and its larger tributaries — the Miami, Little Miami, Licking, and 
Mill creek — dissection of the peneplain has progressed far enough to 
leave few level areas. Farther from drainage lines, in Butler, Warren, 
and Clermont counties, the upraised peneplain becomes the general level, 
over which sluggish creeks meander in valleys little below this level, and 
into which occasional streams are cutting toward the temporary base level 
of the Ohio, nearly 500 feet below. 
Almost the whole of the Cincinnati region has been glaciated. Drifts 
of two epochs, the Illinoian and the Earlier Wisconsin, are represented 
within the area. Over the uplands is spread a covering of drift from five 
to twenty-five feet thick (fig. 2 ). Little of the Illinoian till now remains 
on hillsides or in ravines, but some of the older valleys are partially filled 
with it. It is compact and impervious, for it is composed largely of 
clay, with relatively few and usually small pebbles (Leverett, 1902). 
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