| Bellefonte Formation | |
| Type: | Formation |
| Age: | Lower Ordivician |
| Period: | Ordovician |
| Country: | United States |
| Subunits: |
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| Underlies: | Loysburg Formation |
| Overlies: | Axeman Formation |
| Thickness: | 50' - 2,145' |
The Ordovician Bellefonte Formation is a mapped bedrock unit in central Pennsylvania. It is the uppermost unit of the Beekmantown Group. The top of the Bellefonte is marked by the Knox Unconformity.
The Bellefonte is defined as a medium-gray, brownish-weathering, medium-bedded dolomite and minor sandstone. The very fine grained Tea Creek Member lies above, and the crystalline Coffee Run Member lies below. The Tea Creek Member is a medium gray argillaceous limestone. While still a limestone it does have a high magnesium content. Mostly devoid of fossils. Beds of Chert maybe found about a third of the way through the Tea Creek Member.[1]
Deposition of formations such as the Bellefonte Dolomite occurred in environments equivalent to the modern Bahama lagoons, east of Miami.[2]
Relative age dating of the Bald Eagle places it in the Ordovician period. It rests atop the Axemann Formation,[3] or the Nittany Formation. An example of this, is between Tyrone and Water Street, Pennsylvania. Here the Axemann is missing, and the Loysburg Formation conformably overlies the Bellefonte Formation.[4]