MARYLAND GEOLOGICAL SURVEY 173

most intense disturbance is always observable in the eastern portion of
the range and dies away gradually into the central plains. A second-
ary result of this action from the east is that all the folds are tipped
toward the west and all the great faults show a thrust in the same
direction. In consequence of this the oldest of these sediments are
toward the east and the youngest toward the west, although the more
or less abrupt folds into which they "were thrown, when raised into a
mountain chain, have since been cut off by erosion in such a manner as
to show a repeated succession of strata and at the same time to present
in portions of the eastern border area rocks of still earlier age.

The section made by Maryland across the Appalachian system be-
tween the Frederick valley and the western line of Garrett county pre-
sents an almost complete series of these various formations. As has
been already pointed out, the mountain system of Maryland is divisible
into three distinct physiographic and geologic districts, but as the
features of each division appear to some extent repeated in that which
is adjacent to it, it seems more desirable to treat the geology of the
Appalachian Region as a unit, and describe under each formation its
distribution, character and structure. Reference to the map will
show the relations which these formations bear to the several geo-
graphic divisions.

The following divisions are recognized in the rocks of the Appa-
lachian Region.

FORMATIONS OF THE APPALACHIAN REGION.

Formations of the Appalachian

Region.
PALEOZOIC.

Permian (?)...................... Frostburg.

Carboniferous.................... Elkgarden.

Fairfax.

Bayard. —Coal Measures.

Savage.

Pottsville.

Mauch Chunk.

Greenbrier.

Pocono.
Devonian........................ Hampshire (Catskill).

Jennings (Chemung).
Romney (Hamilton).

Monterey (Oriskany).

Savage.
Pottsville.