a 
.* 
t 
The Peneplain in Georgia. 77 
Tallapoosa and its tributaries, are flowing partly on this old 
surface and partly in channels which they have been able to 
sink but a short distance below it, although it now stands from 
1,000 to 1,400 feet above sealevel. In northern Georgia it merges 
into the Smoky mountain type, differing from the latter in the 
greater perfection to which the baseleveling process was carried 
and in the more perfect preservation from subsequent erosion. 
This peneplain is well preserved in Dug Down mountain, south 
of Rockmart, Georgia, and it is from this plain that the historic 
knobs of Kennesaw and Stone mountain stand up so promi- 
nently. 
When the peneplain was formed it must have extended to the 
margin of the Cretaceous sea which at that time bounded the 
province on three sides; but it is this marginal portion which 
was subjected to the greatest erosion, so that wherever any con- 
siderable elevation took place the peneplain has been wholly 
destroyed. Hence there is a narrow belt within which no data 
are available for reconstructing the peneplain, except by in- 
terpolation from the approximately known position of the sea 
margin and the remnants of the surface still to be found at 
ereater or less distances therefrom. These distances are not 
usually so great as to cause much uncertainty in determining 
the position of the peneplain at any point. 
PHYSIOGRAPHY OF THE CRETACEOUS PENEPLAIN. 
The existing remnants of the Cretaceous peneplain having been 
described in some detail, a fairly complete view may be gained 
of its physiography at the close of the long period of quiescence 
during which it was formed. Although this is the most perfectly 
baseleveled plain ever developed in the province, and although 
it was exceptional for its extent and regularity, it did not have 
a perfectly horizontal surface; in fact, it was level only where 
erosion acted under the most favorable conditions, either near 
sea margin and along the largest streams or where the rocks 
were easily removed by solution. Where soft and hard rocks 
alternated, the former were quickly reduced, while the latter re- 
mained above baselevel for longer or shorter periods, according 
as they were more or less remote from the main drainage lines. 
Where the location was most favorable for erosion, hard and soft 
rocks alike were perfectly reduced, and the rivers wandered in 
sinuous courses and with sluggish currents, uninfluenced by the 
