MARYLAND GEOLOGICAL SURVEY 189

the Piedmont Plateau when the sea occupied the present area of the
Coastal Plain, these later sediments form a series of thin sheets, which
are inclined slightly to the seaward, so that successively later forma-
tions are encountered in passing from the inland border of the region
toward the coast. Oscillation of the sea floor, with considerable
variation both in the angle and direction of the tilting, went on, how-
ever, during the period of Coastal Plain deposition. -As a result the
stratigraphic relations of these formations, which have generally been
held to be of the simplest character, possess in reality much com-
plexity along their western margin, and it is not uncommon to find
that intermediate members of the series are lacking, as the result of
transgression, so that the discrimination of the different horizons, in
the absence of fossils, is often attended with great uncertainty.

The Coastal Plain sediments, deposited after a long break in time
between the red sandstones and shales (Newark formation) of Triassic
age (hitherto described as overlying the crystalline rocks of the west-
ern division of the Piedmont Plateau) and the lowermost of the series
now to be considered, complete the sequence of geological formations
found represented in Maryland. From the time deposition opened
in the coastal region during late Jurassic or early Cretaceous time to
the present nearly constant sedimentation has apparently been going
on, although frequent unconformity appears along the landward
margins of the different formations.

The formations of the Coastal Plain consist of the following:

FORMATIONS OF THE COASTAL PLAIN.

Formations of the

Coastal Plain.
CENOZOIC.

Pleistocene............................ Columbia.

Neocene.............................. Lafayette.

Chesapeake.

Eocene................................ Pamunkey.

MESOZOIC.

Cretaceous............................ Rancocas.

Monmouth.

Matawan.

Raritan.

Patapsco. Potomac
Jurassic (?)............................ Arundel. =Group

Patuxent.