[Footnote 6: The name "Catoctin Belt" is applied to this region
because it is separated by Catoctin Mountain from the Piedmont plain
as a geographic unit more distinctly than in any other area, and
because its geological unity is completed by Catoctin more fully and
compactly than elsewhere.]

In this important work the Catoctin Belt is shown to be an epitome of
the leading events of geologic history in the Appalachian region. It
contains the earliest formations whose original character can be
certified; it contains almost the latest known formations; and the
record is unusually full, with the exception of the later Paleozoic
rocks. Its structures embrace nearly every known type of deformation.
It furnishes examples of every process of erosion, of topography
derived from rocks of nearly every variety of composition, and of
topography derived from all types of structure except the flat plateau
type. In the recurrence of its main geographic features from
pre-Cambrian time till the present day it furnishes a remarkable and
unique example of the permanence of continental form.

With certain qualifications, a summary of the leading events that have
left their impress on the region is as follows:

1. Surface eruption of diabase.

2. Injection of granite.

3. Erosion.

4. Surface eruption of quartz-porphyry, rhyolite, and andesite.