MARYLAND GEOLOGICAL SURVEY 157
TABLE OF MARYLAND FORMATIONS. (Continued. )

		Formations represented in
		Maryland.
	Devonian Period	represented by the Hampshire (Catskill).
		Jennings (Chemuug).
		Romney (Hamilton).
		Monterey (Oriskany).
	Silurian "	" " Lewistown (Niagara — L. Helderberg)
		Rockwood (Clinton).
		Tuscarora (white Medina).
		Juniata (red Medina).
		Martinsburg (Hudson River).
		Shenandoah (upper part).
	Cambrian "	" " Shenandoah (lower part).
		Antietam.
		Harpers.
		Weverton.
		Loudoun.
	ARCHEAN TIME.
	Algonkian and
	Archean (?) "	" " Granite.
		Diorite.
		Basic Volcanics.
		Acid Volcanics.
		Peridotite and Pyroxenite.
		Gabbro.
		Marble.
		Quartz-schist.
		Gneiss.

As has been pointed out in the physiographic description of the
state, Maryland's territory falls naturally into three sharply contrasted
provinces: an eastern coastal plain bordering the Atlantic Ocean and
surrounding the Chesapeake Bay, a central plateau, and a western
region of mountains. These three main physiographic divisions were
found capable of further differentiation into seven topographic belts,
and these seven subordinate regions are each composed of a distinct
series of geological formations. This may be perceived readily by
examining the geological map.

The separateness of the formations is less pronounced in the two
divisions of the Coastal Plain, although the northeast-southwest trend
of the nearly horizontal beds produces a predominance of the later
Cenozoic formations in the eastern division and of the Mesozoic and
early Cenozoic deposits in the western division.