Page 38 - History of Rockingham Co
P. 38
ROCKINGHAM COUNTY
Abedded quartzite. typical exposure of this quartzite is
found at the nose of Peaked Mountain. The formation also
occurs in the Alleghany ridges. Its age is Silurian.
The rocks of the Alleghany ridges are as follows, given
in order of age: (1) the Martinsburg shale and (2) Massa-
nutten sandstone, which have been described above; (3)
Rockwood formation of Silurian age, composed of reddish
micaceous sandstones, which grade upward into reddish and
brown shales capped with a bed of greyish to yellowish
quartzite. The thickness of the formation is about 200 feet.
(4) Lewistown limestone of Silurian age, containing numerous
fossil corals and braciopods and remains of sponges and micro-
scopic organisms. Its thickness is about 100 feet. (5) Mon-
terey sandstone of Silurian and Devonian age, in part cal-
careous. The thickness is about 300 feet. (6) The dark
colored Romney shales of Devonian age, which were deposited
on the eroded surface of the Monterey sandstone. This non-
conformity represents the only break in the sedimentary cycle
within the bounds of Rockingham County. The thickness of
the formation approaches 1000 feet. (7) Jennings formation,
also of Devonian age, which is made up of olive to buff col-
ored shales interstratified with massive fine-grained sand-
stones. Its thickness is about 3000 feet. It is succeeded by
the (8) Hampshire formation, made up of thinly bedded grey
and reddish sandstone and thick bedded sandstone, all inter-
bedded with thin layers of shale. The formation is as thick
as 1400 feet, and it is of Devonian age. (9) The Pocono
sandstone of Mississippian age, v/hich is the youngest of the
sedimentaries in the county. It is composed of light grey
sandstones of a rather coarse texture, which are interbedded
with thin layers of semi-anthracite coal. It is about 700 feet
in thickness.
The structure of the rocks of Rockingham County can best
be understood by reference to the accompanying structure
section. It will be remembered that the sedimentary rocks
of the county were originally laid down by water in the order
in which they now occur, but in a horizontal position. The
-29-
Abedded quartzite. typical exposure of this quartzite is
found at the nose of Peaked Mountain. The formation also
occurs in the Alleghany ridges. Its age is Silurian.
The rocks of the Alleghany ridges are as follows, given
in order of age: (1) the Martinsburg shale and (2) Massa-
nutten sandstone, which have been described above; (3)
Rockwood formation of Silurian age, composed of reddish
micaceous sandstones, which grade upward into reddish and
brown shales capped with a bed of greyish to yellowish
quartzite. The thickness of the formation is about 200 feet.
(4) Lewistown limestone of Silurian age, containing numerous
fossil corals and braciopods and remains of sponges and micro-
scopic organisms. Its thickness is about 100 feet. (5) Mon-
terey sandstone of Silurian and Devonian age, in part cal-
careous. The thickness is about 300 feet. (6) The dark
colored Romney shales of Devonian age, which were deposited
on the eroded surface of the Monterey sandstone. This non-
conformity represents the only break in the sedimentary cycle
within the bounds of Rockingham County. The thickness of
the formation approaches 1000 feet. (7) Jennings formation,
also of Devonian age, which is made up of olive to buff col-
ored shales interstratified with massive fine-grained sand-
stones. Its thickness is about 3000 feet. It is succeeded by
the (8) Hampshire formation, made up of thinly bedded grey
and reddish sandstone and thick bedded sandstone, all inter-
bedded with thin layers of shale. The formation is as thick
as 1400 feet, and it is of Devonian age. (9) The Pocono
sandstone of Mississippian age, v/hich is the youngest of the
sedimentaries in the county. It is composed of light grey
sandstones of a rather coarse texture, which are interbedded
with thin layers of semi-anthracite coal. It is about 700 feet
in thickness.
The structure of the rocks of Rockingham County can best
be understood by reference to the accompanying structure
section. It will be remembered that the sedimentary rocks
of the county were originally laid down by water in the order
in which they now occur, but in a horizontal position. The
-29-
