188 PHYSIOGRAPHY, GEOLOGY AND MINERAL RESOURCES
THE PERMIAN PERIOD.

The rocks which are here questionably referred to the Permian are
confined to the central portion of the George's Creek valley in western
Allegany county where they rest with apparent conformity upon the
Carboniferous deposits below. The single formation recognized in
these rocks of doubtful Permian age is denominated the Frostburg
formation.

THE FROSTBURG FORMATION. —The Frostburg formation, so called
from Frostburg in Allegany county, apparently conformably overlies
the Elkgarden formation of Carboniferous age. It occurs in patches
along the centre of the Georges Creek valley, chiefly in the vicinity
of Frostburg, where erosion has left fragments capping the tops of the
higher lands. The Frostburg formation consists of limestones, sand-
stones, and shales, the limestones occurring in several bands and at
different horizons. The most important of these limestone beds forms
the base of the formation. Sufficiently distinctive fossils have not yet
been obtained from the Frostburg formation and its separation from
the Carboniferous formations below is not yet definitely determined.
The difference in the character of the materials as compared with
the formations below is striking, indicating that the physical condi-
tions had changed prior to the deposition of the materials. The coal
beds of earlier date are entirely lacking and in their place we have
deposits which indicate deeper waters, in which, during much of the
time, little sediment was being laid down. The thickness of the
Frostburg formation is about 250 feet.

THE COASTAL PLAIN.

The area of low land which borders the Piedmont Plateau upon the
east and passes with constantly decreasing elevation seaward has
already been described under the name of the Coastal Plain. It is
part of that great belt of low country which extends from New Jersey
to the Gulf and is made up of geological formations of younger date
than those which have been hitherto described. These later forma-
tions stand in marked contrast to the strata in other portions of the
state in that they have been but slightly changed since they were
deposited. Laid down one above another upon the eastern flank of