Ecology of the Cincinnati Region 
117 
This older drift affects but little the topography of the region, but does 
help to produce poor surface drainage on the flat uplands. 
North of Cincinnati, and extending into Hamilton county in the 
vicinity of Mill creek and the Miami, is the covering of the younger 
drift—the Earlier Wisconsin. This, both in the morainal tract and inner 
border district, commonly contains numerous and often large pebbles 
held in a clayey matrix (Leverett, 1902). 
In many places within the area of Wisconsin glaciation, a distinctly 
glacial topography may be found. Low gently sloping hills, and valleys 
not undrained but still not stream valleys, are common features of the 
upland topography within the area which was covered by the Earlier 
Wisconsin ice. Some areas on the uplands are flat, and except for soil 
differences, are much like those covered only by the Illinoian. As a rule, 
it is the uplands covered with the younger drift which are the better 
drained. Glacial hills occur outside the upland districts, along the west 
side of Mill creek valley from Lockland almost to Hamilton. 
The loess, or white clay, which is associated with the Illinoian 
deposits, is not found north of the Wisconsin glacial boundary. It 
covers the highest terraces and filled valley flats (at an altitude of 600 
feet or more) and is spread out in varying thickness over the upland. 
It is a very fine-grained material which holds water for a long time. 
Outwash gravels from the Wisconsin ice sheet partially filled some 
of the valleys, and now remain as terraces in many places along the Ohio, 
the'two Miamis and Mill creek (Hg. 2 ). These terraces are composed 
of coarse gravels in the northern parts of the area, along the Adiami and 
Little Miami; and of finer material, farther south along the Ohio. The 
gravel, because of its large pore content, has a high water capacity, but 
drains rapidly at the surface, and where exposed on river bluffs. It is 
for this reason that terrace edges are among the most xerophytic habitats 
of the region. 
In most parts of the area, stream valleys cut through the glacial 
deposits, and expose the bed-rock beneath. However, along the small 
sluggish streams of the upland, and in the deeply filled valleys, bed-rock 
is seldom seen. 
The bed-rock is of Upper Ordovician age, and five formations are 
represented in the region (iig. 2 ). Three of these, the Pt. Pleasant and 
the Utica at the bottom, and the Richmond at the top, seldom outcrop 
within the area, and have little or no effect upon the kind of vegetation. 
The other two, the Eden shale and the Maysville (Fairview and McMil- 
