CYCLES OF EROSION IN PENNSYLVANIA 
West Chester is located upon this peneplain sur- 
face, which is the dominant altitude throughout the 
West Chester quadrangle (see Figs. 19 and 20). At 
4oo feet it carries Early Brandywine gravel and sand, 
10 miles west of the ‘‘fall-line” zone. It has been 
named the Early Brandywine from the formation 
which is found at this altitude and on the seaward 
continuation of the slope. This peneplain is corre- 
lated with the so-called Lafayette" terrace recognized 
in Maryland? but a more widespread extension is 
claimed for the Early Brandywine peneplain. 
The Early Brandywine peneplain is everywhere 
submaturely dissected. The summits of the inter- 
stream areas preserve the peneplain, gentle slopes 
from these summit remnants lead to the gorges 
(Pleistocene) of the main streams and of the larger 
tributaries or form the U-shaped valleys of head- 
water streams. These slopes have an elevation 
inland from 300 to 4oo feet and in the “fall-line” 
zone from 200 to 300 feet (see Figs. 21-25). 
Following the deposition of the Early Brandywine 
formation and before the deposition of the Sunder- 
land formation, the whole continental shelf was 
brought above the sea and master-streams of the 
Atlantic plain were extended to the edge of the con- 
tinental shelf. To this period, which may have been 
well within Pleistocene time, is attributed the forma- 
tion of the Late Brandywine benches and slopes. 
Few formations can be correlated with it, as the 
* Owing to the change of the name Lafayette to Brandywine, 
the more recent name has been given to the peneplain. The‘’name 
Brandywine is taken from a village of that name in Prince George 
County, Md., where the formation is reported to be characteristi- 
cally developed. The position and level of the gravel of this type 
locality at 233 feet seem to indicate that it is the low-level Brandy- 
wine or Late Brandywine gravel as it is provisionally named in 
this paper. 
2 Maryland Geol. Survey, Vol. VI (1906), pp. 59-60. 
West Chester Quadrangle 
Harrisburg 
750° 
E Brandywine Gravels 
00" 
Early Brandywine 
555 
Sunderland 
E. Brandywine 
ate Brandywine 
500’ 
250' 
¢ 
Fic. 19.—Section in West Chester quadrangle 
