North Atlantic Pleistocene Problem — Shattiick. 87 
THE PLEISTOCENE PROBLEM OF THE NORTH 
ATLANTIC COSTAL PLAIN.* 
By Geoege Burbaxk Shattuck, Baltimore, Md. 
In that portion of the Atlantic Coastal Plain which lies be- 
tween the Raritan and Potomac rivers there is a mantle of 
loam, sand and gravel covering most of the earlier deposits of 
the lowland and lapping well 110 on the Piedmont Plateau, 
'ihis veneer of unconsolidated deposits has long attracted the 
attention of explorers and various opinions regarding its rela- 
tions and structure have been entertained. The attention of 
the earlier geologists was largely taken up in unravelling the 
history of the more attractive crystalline and fossil-bearing 
rocks, and in problems connected most intimately with glacia- 
tion, and it was not until Mr. W. J. McGee, formerly of the 
United States Geological Survev, undertook the study of these 
sunerficial deposits that their true relations began to appear. 
The conclusions on this subject which Mr. McGee has pub- 
lished from time to time during a period of fourteen years may 
be briefly summarized as follows : 
VIEWS OF MR. \y. J. m'gEE. 
The Lafayette, which is a series of orange-colored loams, 
sands and gravels, extends up, according to Mr. McGee, from 
the south and occupies the divides and higher portions of the 
Coastal Plain of Virginia as far north as Fredericksburg. Dis- 
tinct from these deposits both- in origin and age, is another 
series of loams, sands and gravels designated by him as the 
Columbia formation, which fill the valleys of the present 
streams and mantle the divides between them. This formation 
is divisible into two phases, fluvial and inter-fliivial. The 
fluvial phase is composed of deltas which were deposited under 
water, by those streams in whose valleys they now lie, when the 
land stood lower than it does today. The inter-fluvial phase is 
found on the divides and is a littoral deposit made by the 
waves which beat against the coast at the same time the rivers 
were building their delta^ The two phases are therefore con- 
temporaneous and grade over into one anotl:er. The fluvial 
phase exhibits a distinct bi-partite division. The upper mem- 
ber consists of a brick-clay and loam, and the lower member is 
*From the Johns Hopkins Circulars, No. 152, May, 1901. 
