Ledger Formation
The Ledger Formation or Ledger Dolomite is a geologic formation in Pennsylvania, United States.
| Ledger Formation Stratigraphic range: Cambrian | |
|---|---|
| Type | Formation |
| Sub-units | Lower dolomite member, Willis Run Member, upper dolomite member |
| Overlies | Kinzers Formation |
| Lithology | |
| Primary | dolomite |
| Location | |
| Region | Pennsylvania |
| Country | United States |
| Extent | Pennsylvania, Maryland, Virginia |
| Type section | |
| Named by | Stose, G.W., and Jonas, A.I.[1] |
The Ledger is described as light-gray, locally mottled, massive, pure, coarsely crystalline dolomite. It may be siliceous in the middle part.[2]
Type section
Named from exposures at Ledger, Pennsylvania, formerly 3 miles northeast of Kinzers, Lancaster County, Pennsylvania.[1]
Other outcrops
At Valley Forge National Historical Park, the visitor center parking lot is built within an old quarry of the Ledger, and the former quarry walls are exposed. The rocks contain stromatolites. In the nearby Port Kennedy Quarry, the Triassic Stockton Formation unconformably overlies the folded Ledger.[3]
The Ledger is exposed at a roadcut on the south side of Route 30 at the interchange with Route 23 (East Walnut Street) on the northeast side of Lancaster.
References
- Stose, G.W., and Jonas, A.I., 1922. The lower Paleozoic section in southeastern Pennsylvania, Washington Academy of Sciences, Journal v. 12, no. 5, p. 358-366
- Berg, T. M., Edmunds, W. E., Geyer, A. R., and others, compilers, 1980, Geologic map of Pennsylvania: Pennsylvania Geological Survey, 4th ser., Map 1, 2nd ed., 3 sheets, scale 1:250,000.
- Valley Forge National Historical Park, Montgomery and Chester Counties, The Geologic History, 2nd Ed, 1993. Pennsylvania Trail of Geology, Park Guide 8, Prepared by Department of Conservation and Natural Resources, Bureau of Topographic and Geologic Survey