350 THE COASTAL PLAIN OF NORTH CAROLINA.

under consideration, where the rocks are concealed for the most part
by superimposed sedimentaries, the detailed study of structure is in
most places impossible.

The results of experiments in this area in the past ten or fifteen
rears have shown that the prospects for getting a supply of water of
potable character from this source are good, although there is in the
ease of every atiempt the possibility of failure. Where supplies from
other sources are not available, this possible source should not be left
untested.

By referring to the separate accounts of the water conditions in the
several counties within the belt, detailed information may be had re-
garding individual wells which obtain their supply from this source.
Tt will be observed that successful results have been obtained at various
places from one end of the belt to the other. The largest number of
wells in any given area is in the vicinity of Smithfield and Selma in
Johnston County. The reason for this lies in the fact that this area
is underlain by a slate or phyllite rock possessing definite cleavage
planes along which the water is able to pass, and experience has shown
that the drill seldom fails to penetrate a horizon at some depth less
than 300 feet which will yield moderate to large amounts of water.

In nearly all cases some artesian pressure is exhibited, but so far as
known no wells furnishing sufficient artesian pressure to lift the water
above the surface and produce flows, and obtaining their supply from

rocks underlying the deposits of the Coastal Plain, have been drilled

within the area.
CRETACEOUS.

Patuxent formation.—This formation appears in surface outerops
in a long narrow area running northeast-southwest which extends from
Roanoke River to the South Carolina line (see geologic map, Plate
XVII, in pocket). It rests upon the uneven surface of the underlying
basement rocks. The beds dip gently to the southeast and pass uncon-
formably beneath the overlying Black Creek (“Bladen”) formation, be-
coming deeper and deeper in the direction of the coast. Very little is
known of their coastward extension, but it appears certain that in the
region of the Cape Fear Valley at least they do not extend as far as
Wilmington, as shown by the fact that both at Wilmington and at Fort
Caswell only marine beds of Upper Cretaceous age were encountered
down to the underlying bedrock. Here at least they appear to have
pinched out beneath the overlying Upper Cretaceous beds and the base-
ment rocks on which they rest. In that part of the belt extending from

 

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