From the distribution of these various fragments, inconspicuous as
they are, considerable can be deduced in regard to the environment of
the Weverton sandstone.

The submergence of the Catoctin Belt was practically complete, because
the Weverton sandstone nowhere touches the crystalline rocks. Perhaps
it were better stated that submergence was complete in the basins in
which Weverton sandstone now appears. Beyond these basins, however, it
is questionable if the submergence was complete, because in the
Weverton sandstone itself are numerous fragments which could have been
derived only from the granite masses. These fragments consist of blue
quartz, white quartz, and feldspar. The blue quartz fragments are
confined almost exclusively to the outcrops of the Weverton sandstone
in the Blue Ridge south of the Potomac, and are rarely found on
Catoctin.

The general grouping of the Loudoun formation into two classes of
deposit (1), the fine slates associated with the Weverton sandstone,
and (2), the course sandstones occurring in deep synclines with no
Weverton, raises the question of the unity of that formation. The
evidence on this point is manifold and apparently conclusive. The
general composition of the two is the same--i. e., beds of
feldspathic, siliceous material derived from crystalline rocks. They
are similarly metamorphosed in different localities. The upper parts
of the thicker series are slates identical in appearance with the
slates under the Weverton, which presumably represent the upper
Loudoun.

A marked change in the thickness of the Weverton sandstone occurs