| Tomstown Dolomite | |
|---|---|
| Stratigraphic range: Cambrian | |
 USGS photo 1 mile east of Bakerton, West Virginia | |
| Type | Sedimentary |
| Underlies | Rome Group and Waynesboro Formation |
| Overlies | Antietam Formation and Chilhowee Group |
| Thickness | 200 - 1000 feet |
| Lithology | |
| Primary | dolomite |
| Other | Chert, limestone, shale |
| Location | |
| Region | Appalachia, Mid-Atlantic United States, and Southeastern United States |
| Country | United States |
| Extent | Maryland, Pennsylvania, Virginia,[1] West Virginia |
The Tomstown Dolomite or Tomstown Formation is a geologic formation in Maryland, Pennsylvania, Virginia and West Virginia.[2][3][4] It preserves fossils dating to the Cambrian Period.
In Maryland it is described as "Interbedded light gray to yellowish-gray, thin- to thick-bedded dolomite and limestone; some shale layers; gradational contact with Antietam; thickness 200 to 1,000 feet."[2]
In southern Maryland it is divided into four members:[5]
- Dargan Member Interbedded and cyclical dolomite and limestone.
- Benevola Member Light gray to white, massive to poorly bedded, highly fractured sugary dolomite.
- Fort Duncan Member Medium- to dark-gray, thick bedded, mottled dolomite with white, void-filling sparry dolomite.
- Bolivar Heights Member Three lithologies from the basal layer of a tan, vuggy dolomite, to a light gray dolomitic marble called the Keedysville bed, to thin- to medium bedded layers of lime mudstone containing burrows.
- ^ Paleozoic Sedimentary Successions of the Virginia Valley & Ridge and Plateau
- ^ a b Tomstown Dolomite in Maryland
- ^ Tomstown Dolomite in Virginia
- ^ Tomstown Dolomite in West Virginia
- ^ Brezinski, D.K, and Bell, S.C., 2009. Geologic Map and Karst Features of the Funkstown Quadrangle, Washington County, Maryland. Maryland Geological Survey, Quadrangle Geologic Map FUNKSGEO2009.1. Map Scale: 1:24,000