DEFORMATION OF HARRISBURG PENEPLAIN 295 



rock in the State. The observed slopes of the Harrisburg peneplain also 

 seem to point to the correlation of this peneplain with the even hilltops 

 of the Chemung areas of the northern part of the State, for it has been 

 shown that in all localities, from the extreme eastern part of Penns}^- 

 vania to the shore of lake Erie in the vicinity of Cleveland, the Harris- 

 burg peneplain rises toward the northern-central j)art of Pennsylvania 

 and if the observed slopes of the surfaces were projected toward this 

 central point, they would easily reach the Chemung upland of Tioga 

 and Potter counties. 



Thus the evidence obtained along several independent lines of research 

 seems to point to the correlation of the Chemung upland of the northern 

 part of the state with the Harrisburg peneplain of the eastern and west- 

 ern section, and consequently to its early Tertiary date of origin, and 

 while these conclusions seem to be well supported, they are put forward 

 now only tentatively in the hope that their publication may serve as a 

 stimulus to further investigation. 



DEFORMATION OF THE HARRISBVRO PENEPLAIN 



From the data herein given and from a close study of the topographic 

 maps at present available, the writer has attempted to show by contour 

 lines the deformation of the Harrisburg plain. The result of this study, 

 although of a preliminary character, seems to indicate that the uplifts 

 which have followed the formation of the Harrisburg peneplain have 

 produced an ellipsoidal, dome-shaped structure with its area of maxi- 

 mum development in McKean and Potter counties, in northern Penn- 

 sylvania. The major axis of this structure trends about north 70 degrees 

 east, extending far into Ohio on the west, and probably curving to the 

 north in central New York and extending into the Adirondack region. 

 On the south the evidence is not sufficient to determine the exact form 

 of the uplift, but it seems probable that there is a secondary axis turning 

 to the south and connecting with the main uplift of the southern Appa- 

 lachian region.^ 



Kesume 



Briefly stated, the results of the present study are as follows : 



1. The recognition in the plateau region of northern Pennsylvania 

 and southern New York of the probable remnants of two peneplains. 



2. The provisional determination by comparison with well known 

 areas, of the early Tertiary date of origin of the lower surface, which is 

 carved only on the softer rocks of the region. 



* See plate vi, Geomorphology of the southern Appalachians. National Geographic Magazine, 

 vol. vi, pp. 63-126. 



