Needmore Formation
| Needmore Formation Stratigraphic range: Devonian | |
|---|---|
| Type | sedimentary |
| Lithology | |
| Primary | shale |
| Location | |
| Region | Appalachian Mountains |
| Country | United States |
| Extent | Pennsylvania |
| Type section | |
| Named for | Needmore, Pennsylvania |
| Named by | Willard and Cleaves, 1939[1] |
The Devonian Needmore Formation or Needmore Shale is a mapped bedrock unit in Pennsylvania, Maryland, Virginia, and West Virginia.
Description
The Needmore Formation was originally described by Willard and Cleaves in 1939 as a dark- to medium-gray limy shale, based on exposures in southern Fulton County, Pennsylvania. They considered it part of the Onondaga Group.[1]
DeWitt and Colton (1964) described the Needmore as "soft calcareous medium dark-brownish-gray and greenish-gray shale and mudrock...and soft, slightly calcareous very fissile brownish-black shale" that is not resistant to weathering. They estimated its thickness in their study area as approximately 150 feet.[2]
Fossils
DeWitt and Colton (1964) identified brachiopods (Coelospira acutiplicata, Eodevonaria arcuata), trilobites (Phacops cristata), and ostracods (Favulella favulosa) in the Needmore.[2]
Notable Exposures
Type locality is between Needmore and Warfordsburg in southern Fulton County, Pennsylvania.
Age
Relative age dating places the Needmore in the middle Devonian.
References
- 1 2 Willard, Bradford, and Cleaves, A.B., 1939, Ordovician-Silurian relations in Pennsylvania: Geological Society of America Bulletin, v. 50, no. 7, p. 1165-1198.
- 1 2 deWitt, W. Jr., and Colton, G. W., 1964, Bedrock geology of the Evitts Creek and Pattersons Creek Quadrangles, Maryland, Pennsylvania, and West Virginia: U.S. Geological Surveys Bull. 1179, pl 1 and 2.