NortJi Alhiiific Plcisioccnc Prohlcui — Shatiuck. 91 
the higher terrace levels of the "western shore" of Maryland 
northward to the latitude of Baltimore. Still farther north- 
ward it is confined to outliers on the divides along the western 
margin of the coastal-plain region ; but at the head of Chesa- 
peake bay it extends farther eastward and, in the high Elk 
ridge, caps the Cretaceous and Potomac formations over a con- 
siderable area." 
The Lafayette was also described as continuing down the 
peninsulas of the Coastal Plain. f In this connection he said : 
'T have found tliat the formation extends eastward down the 
coastal plain peninsulas nearly to Chesapeake bay. These pen- 
insulas consist of remnants of an elevated plain, occupied by a 
sheet of Lafayette formation, and originally continuous over 
the entire coastal ' plain. This plain is inclined gently east- 
ward, its altitude decreasing from 500 feet in the Piedmont re- 
gion, to from 60 to 80 feet in the vicinity of Chesapeake bay, 
where it is terminated by an abrupt descent to the low Pleisto- 
cene terrace bordering the bay to- a width of several miles." 
The Columbia of Mr. McGee is found by Mr. Darton to be 
divisible into an earlier and a later member, which are devel- 
oped in well-defined terraces, the former lying normally above 
the latter. The land surfaces upon which the Lafayette and 
Columbia terraces were deposited has been raised and tilted at 
various times in such a manner that' only in that part of the 
Coastal Plain which lies near the Piedmont was the normal 
sequence present, while in that portion bordering on Chesa- 
peake bay the normal sc(|uence was reversed. This state of 
things was brought about in the following way : At the close of 
the Lafayette deposition, the surface on which that formation 
rested was raised and tilted so as to slope eastward toward the 
sea, and after suffering considerable erosion, it was depressed 
in such a manner that its eastern portion was submerged while 
its western margin bordering the Piedmont Plateau remained 
above water. In the estuaries thus formed and along the coast, 
the earlier Columbia formation was then deposited. This for- 
mation, therefore, built up a terrace below that of the Lafayette 
in the heads of the estuaries near the Piedmont, but covered 
up the Lafayette surface where it was submerged to the east. 
While the deposition of the earlier Columbia was still in prog- 
*BvII. Geo/. Soc. Amer., Vol. ii, 1891, p. 445. 
iAiner. Geol., Vol. ix, 1891, p. 181. 
