GEOLOGICAL HISTORY. 301

Some of the larger river channels of this period can be traced across °
the submarine division of the Coastal Plain toward the continental
shelf. Whether these submerged drainage lines were wholly formed at
the close of Lafayette time may be questioned. It is quite possible that
the larger depressions may have already been outlined during earlier
Tertiary epochs. This period of denudation was accompanied by ex-
tensive removal of Lafayette sediments. To the east of the thicker ter-
race accumulations they were apparently removed entirely, since no
remnants of the Lafayette formation have been with certainty recog-
nized beneath the Pleistocene cover except in proximity to the coastal
margin of the Sunderland formation.

PLEISTOCENE,

With the advent of the Pleistocene period the land was again de-
pressed, although not as deeply as during the Lafayette epoch. The
ancient valleys were submerged and the sea gradually transgressed the
interstream areas, removing and reassorting as a result of marine
planation such remnants of the Lafayette as may have been left through-
out this district. Depression at this time earried the sea from 200 to
300. feet above the present ocean level and a fringing terrace was formed
against the Lafayette and older deposits. It can be traced to-day up
the post-Lafayette valleys where it finally merges into the fluviatile
deposits of the upper courses of the streams. It enwraps the unsub-
merged portions of the pre-Lafayette Coastal Plain as well as the
marginal portions of the Piedmont, just as the Lafayette terrace had
enwrapped the still higher elevations during the preceding epoch.

The materials forming the earlier and highest terrace, known as the
Sunderland throughout the middle and northern Coastal Plain, were -
evidently derived in part from reworked deposits of the Coastal Plain,
and were also in part brought down by the Piedmont streams. Deposi-
tion was rapid, since the deposits attained only a moderate thickness
and are generally poorly sorted, cross-bedding being everywhere present.

To the north of the Hatteras axis the sea evidently stood throughout
this epoch at essentially the same elevation, but in southern North Caro-
lina to the south of the Hatteras axis a subordinate change in elevation
took place before the close of the epoch, producing two terraces which
have been already described as the Coharie and the Sunderland. It
seems probable that these conditions will be found extending still
farther to the southward when that region has been more fully studied.

With the close of the Sunderland epoch elevation doubtless again
took place throughout the Coastal Plain. Whether this elevation car-
ried the submarine division of the Coastal Plain above the level of the