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THE QUATERNARY FORMATIONS. 287

principal river valleys. South of Carteret County the Pamlico forma-
tion has only a limited development, being present in places along the
coast and along the valley sides as very narrow bordering terraces. (See
geologic map, Plate XITI, in pocket.)

The Pamlico terrace has been traced northward through Virginia
into Maryland.

The character and age of the strata underlying the deposits of this

formation are but imperfectly known. It is certain, however, that they
are in part of Eocene, in part of Miocene, and in, part of Pliocene age.
It is certain, also, that in parts of the area beds of shell marl of Pleisto-
cene age occur at shallow depths beneath the surface. To which forma-
tions of the Pleistocene these should be referred, however, has not been
determined with certainty.

The upper surface of the Pamlico beds forms a low, nearly level,
plain whose elevation above sea level nowhere exceeds 25 feet. Much
the greater part of the area is made up of vast tracts of swamp land
of which the Great Dismal Swamp which extends into the State from
Virginia is a typical example. Several lakes occupy shallow depres-
sions in this plain. The largest of these is Mattamuskeet Lake in Hyde
County. Others are Alligator Lake in the same county and Phelps
and Pungo lakes in Washington County.

The Pamlico terrace plain, on account of its low elevation and also
on account of the relatively short time since its elevation above sea level
as compared with the older terrace plains, has been subjected to but a
slight amount of stream erosion. It is, therefore, preéminently the best
preserved of the several Columbia terrace plains.

The materials of this formation consist of fine sandy loams, sands
and clays, and to a limited extent of gravels. In the swamp lands the
soils consist in large part of accumulations of peaty matter, which are
of later origin than the main body of the deposits.

The thickness of the deposits is slight, the beds which may be re-
garded as strictly of terrace origin pribanly:3 in but few places exceed-
ing 15 or 20 feet.

But little is known regarding the fossil contents of the deposits. It
is certain that marine shell beds of Pleistocene age underlie portions
of the area. It is possible that much of the region covered by the
Pamlico beds was under water during parts of Pleistocene time pre-

ceding the deposition of the Pamlico material. In this case some of the

Pleistocene shell beds occurring at shallow depths beneath the surface
are in all probability older than the Pamlico formation.

Detailed Sections.—A good exposure showing several feet of sandy ‘

clay overlain by'1 foot of dark to black soil has been noted by B. L.