*Juniata. -Area, 400 square miles; population in 1880,
18,227. This county, 10 miles wide by about 50 miles long, stretches
in a gentle curve between the Tuscarora and Shade mountains from the
Susquehanna River to the bend of the Juniata below Newton Hamilton
on the Huntingdon county line. It is a single trough or basin, on
the two sides of which crop out Clinton and Onondaga shales (V,) Lower
Helderberg limestone (VI,) Oriskany sandstone (VII,) and the central
part of which still preserves the Marcellus, Hamilton, and Chemung
divisions of VIII, but nothing higher in the series, and, therefore,
of course, no coal, although a few thin streaks of carbonaceous slate
(VIII) have led to that belief. The sides of the basin are steep,
and its belly is crimpled into several close folds, which produce
the zigzags which appear on the geological colored map, so that the
northern outcrop of VI and VII if stretched out would measure at least
70 miles, and the southern outcrop 40 miles. For measurements and
descriptions of the formations see Mifflin and Perry counties. The
fossil ore beds have been mined along the Juniata River (which cuts
through Clinton rocks for about 15 miles) and in the low ridges in
front of East and West Shade mountains, back from the river. East
Shade mountain is a sharp anticlinal fold of Medina (IV) split lengthwise,
so that the Loraine shales (III) appear on the crown of the arch in
a secluded vale between the two crest of the mountain. Blue Ridge
is a similar rock wave of No. IV dying east at the river. Between
the two mountains are the "Long Narrows," a basin of No. V, in which
the river Juniata flows. West Shade Mountain is a similar rock arch
of No. IV, but so much higher than the other two that, when it splits
into two crests going south, not only the slates of No. III, but the
limestones of No. II, appear at the surface, and this becomes Black-Log
valley in Huntingdon County. At the eastern point of the county the
basin has a sharp wave in its bottom, which brings up to the surface
on both sides of the Susquehanna River at the mouth of the Mohontongo
creek both the Oriskany sandstone (VII) and the underlying limestone
(VI.)
* The counties of Juniata and Mifflin are mapped together,
and the map is numbered 41.
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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