east mountain, where the rocks of the Oneida sandstone terrace and the underlying slate have both apparently been overturned and dip southward at steep angles, 35°—50°. The effects of the fault are hardly visible along the stream issuing from Allison’s gap, where it probably coalesces with the prolongation of the Jack’s mountain anticlinal, last well observed north of Mechanicsville.
It has already been described how Jack’s mountain, in Union and Snyder counties, consists of two anticlinals holding the slate of No. III at the heads of Triester and New Lancaster valleys along the Mifflin line, with the synclinal of Swift run between. This will appear more distinctly on joining the two maps together.
5. The Swift Run synclinal of the east develops westward into the Beatty's Knob synclinal, creating a bold mountain spur of Oneida sandstone, north and east of Locke’s Mills. Continued westward the line of this trough elevates first the Hudson river slate of III; passes through Naginney’s cave near the railroad station of this name on the Milroy branch of the Pennsylvania railroad in limestone, beyond which the synclinal is not traceable,
It is comparatively obliterated along Tea creek, where the rocks have a south dip all the way from the Triester valley axis to the slate at Reedsville.
6. The New Lancaster Valley[1] anticlinal, corresponding to the southern roll of Jack’s mountain in Snyder county, is similarly obscured after passing through Locke's Mills and Honey Creek station, although it is probable that it bears a direct relation to the axis, which first appearing along the pike in the vicinity of the village of Kishacoquillas, passes a little north of the Union Mills and through the old Greenwood hematite ore-banks south of Belleville, and forms the main axis of the valley, a little south of the pike all the way to the Huntingdon county line. At all events the western end of the Kishacoquillas valley in Mifflin county seems to everywhere show a breadth of about 2 miles of limestone, with but a single anticlinal axis, throwing off comparatively gentle dips.
- ↑ Swartzel Valley of the First Survey.
