Northumberland. - Area, 460 square miles; population in 1880, 53,123.
This county borders on the Susquehanna River for 22 miles above, and
for 21 miles below Northumberland, where the North Branch comes in from
the East. The anticlinal arch of Montour’s Ridge makes a belt of Clinton
shale 4 miles wide at the river, between two outcrops of No. VI limestone.
North of it the Wilkesbarre trough crosses into Union County, as a belt
of No. VIII (three miles wide) to another outcrop line of the limestone
(2 miles below Milton) which runs into Montour county and zig-zags back
again to the river 9 miles higher up. The space inclosed by this semi-circle
is occupied by No. V coming over from Union county on the backs of four
of the Buffalo mountain anticlinals. No. VIII swings round (outside
the semi-circle outcrop of No. VI limestone and No. VII sandstone) into
Lycoming county, making the Muncy Hill range on the county line, 800`
to 900` A.T. The great anticlinal of Shade mountain in Juniata and Snyder
counties crosses the river at Selinsgrove and runs on east as a belt
of Hamilton and Chemung rocks (No. VIII) 4 miles wide on the Columbia
line, and 9 miles wide at the river, where it is split by a point of
No. VI limestone, between two outcrops of Oriskany No. VII, uniting
2 miles from the river. The center line of the Juniata valley trough
(between the Montour ridge and Shade mountain anticlinals) crosses the
river at its fork and runs on east (south of the North Branch) holding
Catskill lower strata. The great trough in which lies the Shamokin and
Mahanoy anthracite coal basins, surrounded by a mountain of conglomerate
XII, a red shale valley XI, and an outside mountain of X, like a frame
of two beads around a picture, shallows up westward so as to bring the
two outside Catskill (IX) outcrops together at the river at Port Trevorton.
At Georgetown the great Tuscarora Mountain anticlinal of Perry and Juniata
counties crosses the river making two ridges of No. VI limestone and
Oriskany sandstone (each four miles long) along the center line of the
great cove of Hamilton and Chemung rocks, around the head of which sweeps
the Mahantongo mountain, first east, and then back south-west through
Schuylkill and Dauphin counties.
On all the outcrops of limestone VI numerous quarries are wrought,
and this is the only mineral of value in the county outside of the
coal field, for the lead and zinc found in this limestone amounts
to nothing practical. Only the west end of the coal field (19 miles
long from Mt. Carmel to the double point west of Trevorton) is in
this county, comprising the three Shamokin basins; the three Mahanoy
basins (all six being in the same grand trough) lie in Schuylkill
County. In the Shamokin Mine Inspection district 21 collieries produced,
in 1883, 1,439,567 tons, to which must be added the production of
the collieries at and south and west of Mt. Carmel, which, although
in this county, are included among the 56 collieries (5,196,530 tons)
reported in the West Mahanoy district. The coal of Trevorton and Shamokin
has a higher percentage of gas (12 to 14) than any other anthracite,
but not enough to rank it with the semi-bituminous coals of Broad
Top and Maryland. Fourteen workable coal beds (with intermediate small
ones of no value) were carefully surveyed and described by Prof. H.D.
Rogers in 1850, and afterwards published in his Geology of Pennsylvania,
1858, Vol. 2, pp.297; the lowest four being in the body of the Pottsville
Conglomerate No. XII, here 600` thick, so beautifully exposed (dipping
40º south) in the two walls of the fine gap which the Shamokin makes
in escaping from the coal field through Big mountain into the red
shale valley outside (precisely as the Susquehanna escapes from the
Wilkesbarre basin at Nanticoke.) the lowest bed (1) overlying the
lowest mass of Conglomerate is 2 ¼ thick; the next (2) above the second
mass of Conglomerate, 7`; (3) 8`; (4) 6`; (5) 75` above the last,
2 ½`. Then (between XII and a small pebble conglomerate higher up)
lie four notable beds (and four others not worthy of attention) (6)
11`; (7) ?; (8) 6`; (9) one bed at Trevorton, but here separated by
a parting fifteen feet thick into two, the lower 9` and the upper
4`. Above the small conglomerate lies a third series, five workable;
and several not certainly workable beds: (10) a specially pure red-ash,
6`, increasing eastward to 14`; (11) fifty feet above the last, 6`,
also very pure. In the Trevorton gap a similar section shows some
variation in the details, the lower beds being thicker than in the
Shamokin gap. (For many interesting facts concerning the different
thickness of the formations in the northern and southern parts of
the county; the coming in of the Selinsgrove series; the abundance
and species of fossils; the curious gravel terraces of as yet unknown
origin between Milton and Muncy; the erratic blocks on top of Montour
ridge and elsewhere; and the difficulty of explaining the rock dams
in the Susquehanna in connection with the now deeply-buried ancient
water-channel of the North Branch; see Report G7.)
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.
Return to Geologic
Maps of Pennsylvania Counties
Copyright © 2000, Pennsylvania State University
Libraries. All rights reserved.
Please send comments to: ems@psulias.psu.edu
Last modified: 5/3/01
|
