280 THE COASTAL PLAIN OF NORTH CAROLINA.
n

Chowan terrace extend up the river valleys, in places. almost entirely
across the Wicomico belt. These estuarine plains are in most places
separated from the Wicomico plain by well-defined escarpments. Nu-
merous clean-cut sections of the formation are exhibited in the bluffs
of all the larger streams where they cross the area of its occurrence.
(See geologic map, Plate XIII, in pocket.)

In position the formation rests unconformably upon older deposits
of the Coastal Plain. North of Neuse River these consist for the most
part of Miocene beds, but in part, especially beneath the estuarine
extensions, of Cretaceous beds. South of Neuse River it rests in part
upon Miocene, in part upon-Eocene, and in part upon Cretaceous beds.
Its upper surface forms a terrace plain which in the main belt slopes
up from elevations of about 50 feet along the southeast edge of the
area to about 90 or 100 feet along the foot of the seaward-facing
escarpment which separates it from the plain above. The reéntrants
which extend up the river valleys slope up to elevations exceeding 100
feet. above sea level at their inland extremities.

The plain has been somewhat dissected by stream erosion, more espe-
cially along the. borders of the valleys and along the escarpments, but
in general the valley incisions are much shallower than in the case of
the older terrace plains. Broad, level stretches exist in the interstream
areas, and some of these form extensive areas of swamp land, locally
termed pocosons, savannahs, and bays. The larger of these swamps
are Angola Bay in Duplin and Pender counties, Holly Shelter Swamp
in Pender County, Great Dover Swamp in Craven and Jones counties,
and Whiteoak Pocoson in Jones County.

: Tn lithologie character the formation consists of sandy clays, sands
and gravels, resembling in a general way those of the Coharie and
Sunderland formations. In nearly all sections the coarser sands, or
sands and gravels, form the basal beds, and, as a rule, show stratifica-
_tion and cross-bedding. These grade upward into finer sands and
sandy clays of uniform texture. Along nearly all the rivers crossing the
belt which have their source inland in the Piedmont Plateau region, the
exposures reveal near the base of the Wicomico deposits numerous erratic
bo ‘ders of quartz and various kinds of crystalline rocks which are in

ler

 

'- *Pocoson:—A tract of level wet land supporting a thick growth of gums, gall berries, bay
tyishes and trees, and other bushes, trees, etc., which prefer a wet soil. : ; i
__Savannah.—A tract of level land having a wet soil except during periods of dry weather,
and supporting grass and other low vegetation, with but a scattered growth of pine or other
trees and bushes, so that a horse or other object of similar size may be seen at a distance of
as Sap send applied to tracts of open prairie land. : a ters

‘ay.—A flat or slightly depressed tract: of greater or less extent, with either wet or dry

Re
soil, supporting a conspicuous growth of bay trees and bushes.