Bear Valley Strip Mine
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The Bear Valley Strip Mine is an abandoned coal strip mine located in Coal Township, Northumberland County, to the southwest of the town of Shamokin, Pennsylvania. It lies in the Western Middle Field of the Anthracite belt in the Ridge-and-Valley Appalachians, where the Pennsylvanian Llewellyn Formation is exposed. The property is owned by the Reading Anthracite Company. [1]
Structural geology
The coal and other overlying rock has been removed by mining down to a resistant sandstone bed, revealing the three-dimensional structures of folding and faulting caused by the Alleghany Orogeny. Students of geology have visited the location for decades due to the quality of exposures.
The central anticline in the valley is often called the "Whaleback".
The sequence of structural deformation is outlined as follows:[1]
| Stage | Deformation event |
|---|---|
| I | Joint formation in coal |
| II | Joint formation with quartz fiber fillings in sandstone and ironstone |
| III | Pressure solution and primary crenulation cleavage |
| IV | Conjugate wrench and wedge faults form |
| V | Large-scale folding |
| VI | Extensional jointing and faulting |
Gallery
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Concretions in the south wall
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View of the east wall from the Whaleback
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Slickensides on a fault plane, south wall. Lens cap 5.8 cm wide.
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Upright Sigillaria in dipping sandstone and shale beds of the north wall. A so-called "Polystrate fossil".
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Another image of the south wall and Whaleback
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Stigmaria root fossils
References
- 1 2 Sequence of structural stages of the Alleghany orogeny at the Bear Valley Strip Mine, Shamokin, Pennsylvania. Nickelsen, R. P. (Dept. of Geology, Bucknell University) Geological Society of America Centennial Field Guide—Northeastern Section, 1987
Coordinates: 40°45.8′N 76°35.7′W / 40.7633°N 76.5950°W