2012 Loysburg Gap
Gifford Pinchot State Park, Pennsylvania
77th Field Conference of Pennsylvania Geologists
Gettysburg Formation
Periglacial boulder fields located at Loysburg Gap, Tussey Mountain, Bedford County, Pennsylvania. Visited July 8, 2012.

GPS 40.15940 -78.36182

Here are some stills from the video:

Diabase has intruded through Triassic sedimentary rocks in the form of a sill at Gifford Pinchot State Park, York County, Pennsylvania. An outcrop of the diabase is shown in the first photo (GPS 40.073839,-76.894869), located at the day use area on the northwest side of Pinchot Lake within the park. Boulders of the diabase are common throughout the park - the second photo shows their typical appearance as seen in the pet loop of the campground. A closeup of an unweathered surface of the diabase is shown in the third photo.

These were taken at the 77th Annual Field Conference of Pennsylvania Geologists, entitled Journey along the Taconic Unconformity, Northeastern Pennsylvania, New Jersey, Southeastern New York, which took place on October 19 and 20, 2012.

The first photo is at Stop 1 in Port Clinton, Pennsylvania, and shows an outcrop of the Bloomsburg Formation, which is nearly vertical there and which shows obvious cleavage at a steep angle to the bedding (GPS 40.580129,-76.027082).

The next shots were taken at Stop 2, the Penn Big Bed Slate Company Quarry (GPS 40.749061,-75.659818), which exposes the Pen Argyl Member of the Ordovician Martinsburg Formation. The first shows an overview of the quarry. The next shows two views of a slab of the slate, cut into a square. The left shot shows a cleavage plane (not a cut surface), and the right shows the orientation of the bedding (vertical dark bands) relative to the cleavage plane. The next two shots are two glacial erratics of the Silurian Shawangunk Formation at the quarry.
(Note: I visited this mine before in

The next group of photos show the Ordovician Beemerville Complex in northern New Jersey, an intrusion of nepheline syenite and related igneous rocks into the Martinsburg Formation. The first shot shows one of the outcrops of the nepheline syenite (see hand samples nj4 and nj5) (approximate GPS 41.241779,-74.685489). The second shows an outcrop of a dike of phonolite (see hand sample nj3). The third shows a boulder of breccia from a diatreme of the complex (see hand sample nj6).

The next photo shows the Shawangunk at the top of Kittatinny Mountain at High Point State Park, New Jersey, facing northwest. This National Geodetic Survey benchmark is there, at approximately GPS 41.321504,-74.661331.

The last photo shows the angular unconformity between the overlying Shawangunk and the underlying Martinsburg Formations exposed at a railroad cut near Otisville, New York.

These two photos show the Triassic Gettysburg Formation in York County, Pennsylvania. The first is an exposure of the typical red beds (siltstone, sandstone, and shale) on the east side of the Kunkle Mill Road bridge over Conewago Creek (GPS 40.065381,-76.863104). The second shows a boulder of the conglomerate member of the formation, at the top of the Conewago Mountains along Crone Road.

Copyright 2012 James L. Stuby. All Rights Reserved.