| Harpers Formation | |
| Type: | Metamorphic |
| Age: | Cambrian |
| Period: | Cambrian |
| Prilithology: | Schist |
| Otherlithology: | Phyllite, shale |
| Namedfor: | Harpers Ferry, West Virginia |
| Namedby: | Arthur Keith (1894)[1] |
| Region: | Appalachia, Mid-Atlantic United States, and Southeastern United States |
| Country: | United States |
| Unitof: | Chilhowee Group |
| Subunits: | Snowden Member (VA), Montalto Quartzite Member (PA) |
| Underlies: | Antietam Formation |
| Overlies: | Weverton Formation |
| Extent: | Maryland, Pennsylvania, Virginia,[2] West Virginia |
The Harpers Formation is a geologic formation in Maryland, Pennsylvania, Virginia, and West Virginia, consisting of schist, phyllite, and shale. It dates back to the early Cambrian period. It is considered part of the Chilhowee Group.
The type section is in gorges of the Potomac River and the Shenandoah River at Harpers Ferry, West Virginia.
The Harpers Formation overlies the Ledger Formation (dolomite) due to a thrust fault in small roadside quarry (currently overgrown) on Pottery Hill, southwest of York, Pennsylvania.[3]