Schuylkill. - Area, 840 square miles; population in
1880, 129,974. This is the richest county in Anthracite coal; the
southern field, or Pottsville basin, having a run across it of 38
½ miles, along the Sharp mountain and 41 ½ miles along Locust mountain,
Mine Hill and Thick mountain, from the Carbon to the Dauphin county
line. The Mine Hill basin is 14 miles long. The New Boston basin 4
½, and the Mahanoy basin 18 along its southern edge, and 12 along
its northern, passing west into Columbia county. Four of the basins
of Luzerne County also have runs of from 1 to 4 miles in Schuylkill.
In 5 mine-inspectors’ districts, west of Tamaqua, 64 collieries produced
in 1883 2,134,000 tons; and in the 2 inspectors’ districts in the
Mahanoy basin (one fourth of one of them being in Northumberland county)
74 collieries produced 6,630,000 tons. All the coal basins are in
the northern half of the county, being separated from each other by
anticlinal waves of Pottsville Conglomerate No. XII (1000` thick);
from beneath which rises the Mauch Chunk Red Shale No. XI (3000` thick)
forming the floor of Catawissa valley in the north of Locust Valley
in the east, and of Deep creek and Mahanoy valley in the west; also
Wiconisco valleys, between the two western arms of the Pottsville
basin; also the long, narrow, nearly straight valley running across
the county next south of the Sharp mountain. This, the last outcrop
of Red Shale No. XI in the State towards the south-east, crosses the
Schuylkill River at Mount Carbon, 1 mile below Pottsville. The various
coal basins are traversed lengthwise by secondary, sharp, parallel
rolls, two of which sub-divide the Mahanoy field into three sub-basins;
one sub-divides the western end of Mine Hill basin into two sub-basins;
six issue from the Sharp Mountain spurs opposite Patterson, and run
through the Pottsville coal field across Mill creek, and across the
West Branch, past Minersville, into the spurs of Thick mountain, making
4 principal sun-basins at Forestry, Llewellyn, Taylorville and Woodville;
while the two rolls in Fishing Creek mountain add three more sub-basins
at Tremont. The deepest part of the Pottsville field (3000`) is under
a hill south of Minersville. The lower coal beds outcropping along
the north slope of the Sharp mountain, past Pottsville, descend vertically
to a depth of between 2000` and 3000`; and then they gradually rise
northward (rolling several times) to appear at the surface, on a dip
of about 30º, along the south slope of Mine Hill, where a range of old and extensive
collieries work the Mammoth bed, here showing sometimes a thickness
of 60`. It has many partings of slate, two of which increase so much
in size going west as to convert the Mammoth into three distinct coal
beds, which at length get to be 100` more or less apart! This however
is constantly happening with all the larger beds in all parts of the
region, and is the principal cause of the confusion of names given
to the bed, of the difficulty of certainly identifying some of them
in different collieries, even on neighboring tracts, but especially
in different main basins, and of the dissimilarity of the vertical
sections drawn to one scale, and published on sheets in the Atlases
of the Survey. The difficulty has been further increased by the value
of a name as a trade-mark, the old "Diamond," or the old "Primrose,"
for example, names of the purest coal beds in the region, applied
by other operators to their own coal coming from other beds. The chief
practical distinction is that between the lower white-ash and
the red-ash beds above the Mammoth. A general idea of the relationships
of the coal beds to the strata which separate them may be got from
the old Carey shaft at St. Clair: Rock and slate, 119; Primrose
bed, 3`; rock and slate, 68`; Holmes bed, 4 ½`; rock, 65`;
coal, 1`; slate, 51`; coal, 2`; rock, 72`; Sevenfoot coal,
8 ½`; slate, 14`; Mammoth bed, 22`; total, 439 feet.
*On Mill Creek east of Pottsville the First Survey measured
2700` of measures, embracing 36 coal beds, divisible into six groups.
(1,) Upper red ash: consisting of the South Salem at the
top, Salem, Weasel, North Salem, Faust, Nest, Rabbit Hole, and Little
Tunnel, in 700` of rocks; (2,) Middle red ash: Peach mountain,
Lower Peach Mountain, Little Tracy, Tracy, Yard (or Clinton), in 300`;
(3,) Lower red ash: Thin coal, Peacock, Little Peacock, two
unnamed coals, Little Diamond, South Diamond, Diamond, in 435`; (4,)
Gray ash: Hancock, Orchard, Primrose, Flowery field, in 430`;
(5,) Upper white ash, six coals (including Pinkerton’s Mammoth
22`), in 310`; (6,) Lower white ash: five coals (including
the Big Johns’ Co. bed 25`) in 500`. (See Roger’s Geol. Pa., 1858,
Vol. II, p.229.) On the West branch west of Pottsville the same six
groups show different details; measure 2800` total thickness at Westwood;
and have different names and very different thicknesses for the coal
beds. Thus, Group (1) of 200` has 5 beds, none over 4`: Group (2)
of 250`, 4 beds, Skidmore (bottom), Mammoth, Black heath, and Black
valley (top); Group (3) of 350`, 3 beds; Group (4) of 775`, 7 beds;
Group (5) of 400`, 4 beds; Group (6) 700` or 800`, 5 to 7 beds. The
Mammoth in the Mahanoy field reaches 70` in thickness; but its average
in the region may be called 30`.
The Sharp Mountain is cut through to its base by
the Little Schuylkill at the eastern end of the county; by the Swatara
at the western end; and in the center by the main Schuylkill and by
its West branch, these two gaps being 3 miles apart. In the Tamaqua
gap the Conglomerate dips north about 50º
; but in the other three gaps it stands vertical, with the lower coal
beds on one side of it, and the Red Shale on the other. The Schuylkill
river makes here one of the finest geological sections in the State,
through 15,000` of vertical strata, in the three miles from Pottsville
down to the great Orwigsburg anticlinal at Schuylkill Haven; measured
by the First Survey thus: Pottsville Conglomerate (XII) in Sharp mountain
1030`; Mauch Chunk red shale (XI) 2950`; Pocono sandstone (X) in the
north half of Second mountain 1800`; Catskill (IX) in the south half
of Second mountain say 6000`; Chemung and Hamilton in Little mountain
say 3000`. The Orwigsburg anticlinal is vertical to the north and
only 20º to
the south; dies out westward at Pinegrove; but makes the northernmost
long spur of the Blue Mountain beyond the Little Schuylkill. South
of it lies a Chemung basin holding a strip of Catskill in the form
of a long ridge the southern slope of which called Summer Hill, looks
down upon a valley of Marcellus and Clinton shales (the limestone
VI and the Oriskany sandstone VII being nearly or quite wanting here,
as are also the fossil ore beds) rising upon the back of the Blue
mountain, through which the Schuylkill and Little Schuylkill (joining
at Port Clinton) make a fine gap, in which the Medina and Oneida sand
rocks (IV) are seen standing vertical, and against their under-side
abut the edges of nearly horizontal slates (III). A map of this gap,
with the fault, is published in Report D3, Vol. I. Ten
anticlinal rolls come through the mountain and die out west of the
Little Schuylkill in the seven miles above the gap.
* The intervals however are too large owing to the dip.
From: A geological hand atlas of the sixty-seven
counties of Pennsylvania :embodying the results of the field work
of the survey, from 1874 to 1884. By J. P. Lesley. (Report of
progress (Geological Survey of Pennsylvania), v. X ) Harrisburg, PA
: Board of commissioners for the second geological survey, 1885.
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