|2004||Burkholder Quarry, Pennsylvania
Skytop Roadcut, Pennsylvania
Natural Bridges, Kentucky
These are photos from the Burkholder Quarry, operated by the Martin Limestone Company, in New Holland, Pennsylvania. I was doing a geophysical survey along the south wall of the quarry but we were allowed to go in to look around at the end of the work, on August 17, 2004. The photos show Triassic (?) diabase dikes intruding into the Ordovician Epler Formation (limestone).
The first shot shows a pair of dikes exposed in the south wall of the quarry, and the second is a closeup of the one on the left. I collected this specimen (dbq1) here.
The third shows another dike in the north wall, and the fourth is a closeup of contact of the dike (top) and the limestone (bottom). I collected this specimen (dbq2) here.
The last photo shows how folded some of the limestone is in the quarry (in the northwest corner of the quarry).
||These are photos from the Skytop roadcut at Bald Eagle Mountain, Centre County, PA. It is part of the I-99 project in the State College area. I visited the site on a fieldtrip with the participants of the Conference on Principles of Acid Pollution Control Along Highways on Dec. 21, 2004.
The first photo shows an overview of the entire roadcut. The stratigraphy there consists of the Ordovician Bald Eagle Formation (left), the Ordovician Juniata Formation, and the Silurian Tuscarora Formation (right).
The reason for the conference was that there was an unexpectedly large quantity of pyrite and other iron-sulfur minerals primarily in the Bald Eagle Formation, and upon excavation and exposure of the pyrite to air and water, large quantities of sulfuric acid have been generated in the area. The second photo shows some of the pyrite in the Bald Eagle Formation (from under the bridge on the left of the overview). Scale bar is 1 cm. Here is a photo of a rock collected there (st1).
The third photo, primarily of academic interest, shows a redox front in the Juniata Formation. The beds are vertical and strike left to right across the photo, but there is a clear color change in the rocks perpendicular to bedding. The red beds on the left (the typical color of the Juniata Formation) are oxidized, but the beds on the right are reduced. Dr. Duff Gold, one of the fieldtrip leaders, said this is the best exposure of a redox front he has seen. Click here to see Duff's report on the geology of the roadcut.
||These are photos from a roadcut at exit 120 along I-75 north of Lexington, Kentucy. They show the Ordovician Lexington Limestone with large stromatoporoids (probably the Stamping Ground Member). Photos taken Dec. 29, 2004.|
||These are photos from the vicinity of Gray's Arch in the Natural Bridges/Red River Gorge area of Daniel Boone National Forest in east-central Kentucky, taken Dec. 30, 2004. Around 40 arches can be found in this area of Kentucky, where the bedrock consists of Mississippian and Pennsylvanian sandstones, shales, coal, and some limestone. The arches are mostly found in the Pennsylvanian Corbin Sandstone. The first photo shows Gray's Arch. Nearby is a "cave" or overhang where spectacular veins of hematite can be seen in the walls of rock. The second photo shows the cave (with, l to r, Nat Albers, Scott Newcomer, and Rebecca Wells-Albers), and the third photo (with Rebecca) shows the hematite veins, like a black net on the rock. The fourth photo, also nearby, shows a closer view of some of the hematite veins.|