Hamilton Group
| Hamilton Group or Millboro Shale | |
|---|---|
| Stratigraphic range: Eifelian - Famennian | |
| Type | Group |
| Sub-units | Western Pennsylvania and West Virginia:
New York and Central Pennsylvania:
|
| Underlies | Tully Limestone and Harrell Shale |
| Overlies | Onondaga Limestone |
| Thickness | up to 2,500 feet (800 m) |
| Lithology | |
| Primary | Shale |
| Other | Limestone, Siltstone, Claystone |
| Location | |
| Region | Appalachian Basin of eastern North America |
| Extent | Maryland, New York, Pennsylvania, Virginia, West Virginia and Ontario, Canada |
| Type section | |
| Named for | Hamilton, New York |
| Named by | James Hall |
The Hamilton Group is a Devonian-age geological group which is located in the Appalachian region of the United States. It is present in New York, Pennsylvania, Maryland, Ohio, West Virginia, northwestern Virginia and Ontario, Canada, and is mainly composed of marine shale with some sandstone.
There are two main formations encompassed by the group: the Mahantango Formation and the Marcellus Shale. In southwestern Virginia, where the two sub-units are not easily distinguishable, the Hamilton Group is broadly equivalent to the Millboro Shale or Millboro Formation.
The group is named for the village of Hamilton, New York. These rocks are the oldest strata of the Devonian gas shale sequence.
