Needmore Shale Explained

Needmore Formation
Type:sedimentary
Age:Emsian[1]
Period:Emsian
Prilithology:shale
Namedfor:Needmore, Pennsylvania
Namedby:Willard and Cleaves, 1939[2]
Region:Appalachian Mountains
Country:United States
Underlies:Marcellus Shale and Millboro Shale
Overlies:Oriskany Formation
Extent:Maryland, Pennsylvania, Virginia, and West Virginia

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.[2]

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 (southern Bedford County, Pennsylvania, and most of Allegany County, Maryland) as approximately 150 feet.[3]

Fossils

DeWitt and Colton (1964) identified brachiopods (Coelospira acutiplicata, Eodevonaria arcuata), trilobites (Viaphacops cristata), and ostracods (Favulella favulosa) in the Needmore.[3]

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.

Notes and References

  1. http://hdl.handle.net/10919/19078 Paleozoic Sedimentary Successions of the Virginia Valley & Ridge and Plateau
  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.
  3. 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. http://ngmdb.usgs.gov/Prodesc/proddesc_20940.htm