Page:Report on the geology of the four counties, Union, Snyder, Mifflin and Juniata (IA reportongeologyo00dinv).pdf/56

28 F³. extreme south corner of Snyder county by elevating the Oriskany sandstone and Lewistown limestone to daylight at McKee’s Half-Falls, passing through Georgetown in Northumberland and making a fertile little limestone valley two miles in length. It is of comparatively small importance in Snyder county.

The structural features of Mifflin county are virtually a westward extension of those described in Union, just as those of Juniata have corresponding folds in Snyder county.

The Buffalo mountain range however, which makes so prominent a feature of the topography and geology of northern Union, is largely absent in Mifflin county, the most of its component ridges extended into Centre county on the north to form the classic “Seven Mountain Range” so beautifully described in the Final Report of the First Survey and delineated in the contour line maps of Mr. C. E. Billing, accompanying this report.

1. The Long mountain synclinal, corresponding to the Hartleton synclinal of Union, continues that axis west from Penns creek along the valley of Panther run, first in lower Clinton shales, and finally in a closely compressed fold of white Medina sandstone. IVc.

Paddy’s mountain, to the north of this in Mifflin county, is a monoclinal, its rocks dipping southeast towards Panther creek and flanked north by the Poe valley of No. III slate in Centre county, whose anticlinal extends westward into Mifflin county again in the northern corner of Armagh township, where it has sank to carry on its crest only the red Medina at the head of Laurel run. Long mountain synclinal deepens again along a right hand fork of Laurel creek, enclosing a considerable area of the lower Clinton rocks No. V. The elevated area west of Laurel creek, associated with the Broad mountain range of Huntingdon county is somewhat complicated by a Z-shaped fault in Brown township.

2. The Broad mountain anticlinal, of Huntingdon county, increasing in strength coming eastward, carries the