Mercer. - Area, 660 square miles; population in 1880, 56,161. The
Shenango river flows south down the western side of the county making
a great bend to the east through Delaware township, and another to
the west in Hickory township, where, at Sharon, it approaches the
Ohio State line within one mile, and two miles below Sharon within
a quarter of a mile. Otter Creek flows south through the middle of
the county to join the Neshannock at Mercer. Wolf Creek flows south
through Worth, Wolf creek, Pine and Liberty to the south-east corner.
Sandy Creek drains the north-eastern quarter eastward into Venango
County. 21 patches of the Clarion coal bed have been preserved on
the high divides in the eastern and southern townships, two of which,
in Pine and Liberty, are of considerable size, and support smaller
overlying, isolated areas of the Ferriferous limestone. 4 hill-tops
south-east of Jackson Centre contain the limestone; another at Henderson
post-office; and two others on the Lawrence line in Springfield township.
The hills on the Butler county line on each side of Wolf creek are
high enough to take in the Kittanning coal (2`) and the Darlington
coal (3`). The Ferriferous limestone is 12 to 15 feet thick along
Wolf creek, south of Pardue in Finley township it does not seem to
exist, and the bore holes south of Stoneboro in Lake township did
not find a trace of it. It seems to be absent also in the high, narrow
ridge south of Greenfield in Lackawannock Township. At the quarries
in Jackson township it is from 9` to 12` thick, the top layers having
been planed off in the ice age, and scratched and covered with drift,
which may conceal it also in Boreland’s knob in New Vernon township,
and in a very high knob in French Creek township, near the Crawford
line. The northern drift covers the entire county, even on the very
summit of Keel ridge in Hickory township 1250` A.T. Bowlders of large
size are often found in the drift; granite, gneiss, greenstone from
New York or Canada, mixed with limestone, sandstone, shale, pieces
of coal, and an abundance of bluish-white clay. Oakland shaft No.
1 struck a large granite bowlder in blue clay 60 feet below the present
surface. A bore-hole at Stoneboro went through clay, sand, gravel
and bowlders 60`, blue clay 30`, total 90`. The whole surface of the
county is dotted with loose bowlders, some of them 10` in diameter,
which were once no doubt enveloped in clay and sand now washed away
from them. Some of the valleys are filled with drift to a considerable
extent, and swamps like that on the low divide between the head of
Little Shenango river and the head of Sandy creek, represent ancient
ponds produced by dams of drift left by the ancient glaciers on their
retreat. The ancient valley bed of the Pymatuning at its junction
with the Shenango has been filled up 100` to the present surface of
the Tamarack swamp. A deserted buried valley, once occupied by the
Shenango, extends along the line of the Erie and Pittsburgh R.R.,
from Clarksville station to Shenango station, between hillsides 200`
high. A bore-hole 63` deep through silt did not strike bed rock. The
Neshannock valley ancient bed near Leesburgh station (New Castle and
Franklin R.R.) has been filled with drift more than 80`. The Scrub-grass
coal bed, less than 1` thick, is found underlying every exposure of
the Ferriferous limestone. The Clarion coal bed (20` below the limestone
in Beaver County) has not been seen in Lawrence. The Brookville (Pardoe)
coal bed, ranging from 40` to 70` below the limestone is mined at
many places in Findley, Jackson, and Lake townships, 3` to 5` thick,
by companies shipping from 100,000 to 150,000 tons per annum. The
bed lies on the Homewood sandstone (XII d) 50`, under which lie the
two Mercer coals, the two Mercer limestones, and the three Mercer
iron-ore beds, all small, in 70` of shales. Then the Connoquenessing
upper sandstone (XII c) 40`, under which lie the Quakertown coal and
iron ore, both small, in 50` of shales. Then the Connoquenessing lower
sandstone (XII b) 30`, under which lies the Sharon block coal in 30`
of shales, over the Sharon conglomerate (XII a) 20`. The Mercer iron
ore plates of carbonate of iron where they reach a thickness of 1
½` or 2` have been mined along their outcrops, for the Oregon, Iron
City, Clay, Sharpsville, and Mineral Ridge charcoal furnaces. The
Mercer coals sometimes reach 3` in thickness. The Quakerstown coal
reaches 3` in N.E. Worth, and has been mistaken formerly for the Sharon
coal, which itself varies from 2` to 5`, and most of its mines are
confined to Hickory township. Its roof shales are rich in fossil plants.
The coal is one third gas, very free from ash, and requires no coking
for blast furnace use. The Sharon conglomerate changes to a beautiful
flagstone at Greenville quarries. It is finely striated by ice where
exposed, contains fragments of wood; and fish spines, teeth, and scales
are often abundant. Under lie the Shenango shales and flagstone 45`;
the Shenango sandstone (Sub-Olean flat pebble conglomerate of McKean
county) with nodular iron ore and fish remains, 15`; and the Crawford
shales, 90` of which are visible in the north-western corner of the
county.
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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