Forest. - Area, 430 square miles; population in 1880,
4,385. This little rectangular wilderness, 2000` A.T., stretching
from the Allegheny River eastward across the high divide, 30 miles,
to the Clarion waters of Elk County, is deeply trenched lengthwise
by the valley and side vales of Tionesta Creek, along the steep
sides of which runs the outcrop of XI, over flat Pocono measures X,
and beneath cliffs of conglomerate XII, containing the thin Alton
and Marshburg coal beds. None of the Productive coal measures
remain upon the flat upland divides. The Venango oil sand formation
underlie the bed of the Tionesta at Foxburg..feet, and has produced
a good deal of petroleum. (See Report R2 and Report I3,
p.133, section 55.) The group here consists of six sands-20`, 10`,
15`, 20`, 30`, and 20 thick-separated by intervals of 82`, 43`, 10`,
45`, and 30`. Three red shales make the group remarkable in this district,
the upper one 40` thick in the middle of the first interval; the middle
one 13` thick in the middle of the second interval; and the lower
one 10` thick on top of the Fifth oil sand. The whole group is 325`
thick, and the plane of its base at Foxburg is only 20 feet above
ocean level. From Foxburg to Parker. The formations in this county
are nearly horizontal, the average dip being less than common railway
gradients; and the surface being almost a continuous forest, presents
few exposures even of a broken and uncertain character; while the
oil wells show that the beds and groups of beds vary in thickness
in every direction. Coal-openings are more numerous near Marienville
in Jenks township than elsewhere, but even trial pits have been gradually
discontinued owing to the abundance of wood and the general use bore-hole
gas for light and fuel. Most of the trial pits are isolated and cannot
be used for constructing a classified system of the beds, none of
which seem to be of noteable size, or suitable for future mining operations.
The summits and divides are commonly patches of massive sandstone
or conglomerate, all referred in former years to one called the Tionesta
sandstone; now, to the three members of No. XII, described in McKean
County, Johnson run conglomerate, Kinzua Creek sandstone,
and Olean conglomerate; between which lie the Alton
and Marshburg small coal beds; and above the upper one
the Clarion coal (2` 3") at Pine Ridge in Jenks township (1742`
A.T.); over which lie 50` of shales. The Ferriferous limestone
seems wanting (by erosion) from the whole country. Col. Hunt’s
summit at Marienville cross roads (1805` A.T.) is Johnson’s
run rock 65`; Alton coal 3`?; shales 10` to 15`; Kinzua
creek upper rock 50`; soft measures and coal? (?); lower
rock 40`; Marshburg upper coal 2`? Olean conglomerate.
Bog iron ores occur in various places, produced by springs issuing
from ferruginous shales between the great sandrocks. The summits west
of the Allegheny River are lower, the highest measured was 1680` A.T.
The Brookston anticlinal axis crosses the South Branch of Tionesta
at Brookston on the Warren County line and runs past Marien (2m. N.W.)
to the south-west corner of Farmington township. The Fifth anticlinal
crosses to Clarion 2 miles above Millstown. The axis of the intermediate
Kane synclinal basin cuts across the great bend of spring creek.
The oil well at Marien gives the following section: Mouth 1615` A.T.,
Drift 8`, SS. 30`, slate 21`, coal 3`, pebbly SS. 98`, slate 25`,
SS. 70`, slate (red?) 70`, white SS. 45`, black slate 85`, SS. 100`,
slate 20`, close pebble SS. 13`, blue slate 204`, (total X, 500`);
red shale 25`, black slate 18`, red shale 76`, black
slate 12`, slate and shells of sandstone 30`, gray SS. 15`, red
shale 10`, black slate 25`, gray SS. 20`, black slate 25`, shells
15`, red shale 15`, (total IX, 286`); black slate 114`, shells
of sandstone 15`, red slate 20`, slate and shells of sandstone 83`,
(total Chemung bored through 232`.)
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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