| Helderberg Group | |
|---|---|
| Stratigraphic range: Lochkovian-Emsian ~ | |
| Type | Group |
| Sub-units |
|
| Underlies | |
| Overlies | |
| Lithology | |
| Primary | Limestone |
| Other | Dolomite, Chert |
| Location | |
| Region | |
| Country | United States |
| Type section | |
| Named for | Helderberg Escarpment |
| Named by | Conrad, T.A. 1839 |
The Helderberg Group is a geologic group that outcrops in the State New York, Pennsylvania, Maryland, New Jersey, and West Virginia. It also is present subsurface in Ohio and the Canadian Providence of Ontario It preserves fossils dating back to the Early Devonian and Late Silurian period. The name was coined by T.A Conrad, 1839 in the New York State Geological Survey Annual Report. Named for the Helderberg Escarpment or Helderberg Mountains.[1]
The upper portion of the Helderberg, or the Kalkberg Formation is host to the Bald Hill ash bed, dated to 417.6 million years ago.[2]
The Helderberg is composed chiefly of limestone and dolomite.[3]
In Maryland and southern Pennsylvania, the Helderberg is divided into three formations. These are the New Creek Limestone, the Corriganville Limestone, and the Mandata Shale. The total thickness is about 60 feet. The formations weather easily and are poorly exposed except in cuts and quarries.[4]
- ^ Berdan, Jean. "The Helderberg Group and the Position of the Silurian-Devonian Boundary in North America" (PDF). United States Geological Survey.
- ^ Ver Straeten, Charles; Ebert, James R.; Bartholomew, Alex; Benedict, Lucas; Matteson, Lucas; Shaw, George. "DEVONIAN STRATIGRAPHY AND K-BENTONITES IN THE CHERRY VALLEY – SCHOHARIE VALLEY REGION". Research Gate.
- ^ Demicco, Robet V.; Smith, Jason. "COMPARATIVE SEDIMENTOLOGY OF THE HELDERBERG GROUP IN CENTRAL NEW YORK" (PDF). New York State Geological Association.
- ^ Glaser, J.D., and Brezinski, D.K., 1994, Geologic map of the Cumberland quadrangle, Allegany County, Maryland, Maryland Geological Survey, Scale 1:24,000.