The Ledger Formation or Ledger Dolomite is a geologic formation in Pennsylvania, United States. The Ledger is described as light-gray, locally mottled, massive, pure, coarsely crystalline

dolomite Dolomite may refer to: *Dolomite (mineral), a carbonate mineral *Dolomite (rock), also known as dolostone, a sedimentary carbonate rock *Dolomite, Alabama, United States, an unincorporated community *Dolomite, California, United States, an unincor ...

. It may be siliceous in the middle part.

Type section

Named from exposures at Ledger, Pennsylvania, formerly 3 miles northeast of Kinzers, Lancaster County, Pennsylvania.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. 358-36

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Other outcrops

Harpers phyllite over Ledger dolomite Sgw01319

Valley Forge National Historical Park Valley Forge National Historical Park is the site of the third winter encampment of the Continental Army during the American Revolutionary War, taking place from December 19, 1777, to June 19, 1778. The National Park Service preserves the site a ...

, 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 An unconformity is a buried erosional or non-depositional surface separating two rock masses or strata of different ages, indicating that sediment deposition was not continuous. In general, the older layer was exposed to erosion for an interval o ...

overlies the folded Ledger. The

Harpers Formation 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. Notable ex ...

overlies the Ledger Formation due to a thrust fault in small roadside quarry (currently overgrown) on Pottery Hill, southwest of York, as shown in the historical photo at left. 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.

Quarries

The quarry currently operated by

Vulcan Materials Company Vulcan Materials Company () is an American company based in Birmingham, Alabama. It is principally engaged in the production, distribution and sale of construction materials. Vulcan is the largest producer of construction materials, primarily gra ...

in Edgegrove, Pennsylvania (west of Hanover) primarily mines the Ledger Formation for aggregate.''Summary groundwater resources of Adams County, Pennsylvania'' by Taylor, L.E., and Royer, D.W., Pennsylvania Geological Survey. Water Resource Report 52. Map Scale: 1:50,000. 1981.
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References

Cambrian geology of Pennsylvania {{Pennsylvania-geologic-formation-stub