The Rockwell Formation is a late

Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, whe ...

and early Mississippian mapped bedrock unit in

West Virginia West Virginia is a state in the Appalachian, Mid-Atlantic and Southeastern regions of the United States.The Census Bureau and the Association of American Geographers classify West Virginia as part of the Southern United States while the Bur ...

Maryland Maryland ( ) is a state in the Mid-Atlantic region of the United States. It shares borders with Virginia, West Virginia, and the District of Columbia to its south and west; Pennsylvania to its north; and Delaware and the Atlantic Ocean to ...

, and

Pennsylvania Pennsylvania (; ( Pennsylvania Dutch: )), officially the Commonwealth of Pennsylvania, is a state spanning the Mid-Atlantic, Northeastern, Appalachian, and Great Lakes regions of the United States. It borders Delaware to its southeast, ...

, in the United States.

Description

The Rockwell Formation was described at its type section at Rockwell Run in West Virginia as soft

arkosic Arkose () or arkosic sandstone is a detrital sedimentary rock, specifically a type of sandstone containing at least 25% feldspar. Arkosic sand is sand that is similarly rich in feldspar, and thus the potential precursor of arkose. Quartz is c ...

sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates) ...

, fine hard conglomerate, and buff hackly

shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4) and tiny fragments (silt-sized particles) of other minerals, especial ...

. The formation was originally described in West Virginia by Stose and Swartz (1912). It was first described in Maryland by H. E. Vokes (1957),Vokes, H.E., 1957, Geography and geology of Maryland: Maryland Geological Survey Bulletin, no. 19, p. 243. and later described in central Pennsylvania by C. R. Wood (1980).Wood, C.R., 1980, Summary groundwater resources of Centre County, Pennsylvania: Pennsylvania Geological Survey Water Resource Report, 4th series, no. 48, p. 60.

Stratigraphy

The Rockwell is generally considered a

Formation Formation may refer to: Linguistics * Back-formation, the process of creating a new lexeme by removing or affixes * Word formation, the creation of a new word by adding affixes Mathematics and science * Cave formation or speleothem, a secondar ...

. At Formation rank, it has several members, including the Patton and Riddlesburg Shale Members,Kammer, T.W., and Bjerstedt, T.W., 1986, Stratigraphic framework of the Price Formation (Upper Devonian-Lower Mississippian) in West Virginia: Southeastern Geology, v. 27, no. 1, p. 13-33. and the Finzel Tongue. It has been reduced in rank to a member of the Price Formation in West Virginia. The Rockwell is a lateral equivalent of the

Huntley Mountain Formation The Huntley Mountain Formation is a late Devonian and early Mississippian mapped bedrock unit in Pennsylvania, in the United States. Description The formation is composed of relatively soft grayish-red shale and olive-gray sandstone. It is lo ...

and the Spechty Kopf Formation, as all three underlie the prominent

Pocono Formation The Mississippian Pocono Formation is a mapped bedrock unit in Pennsylvania, Maryland, and West Virginia, in the United States. It is also known as the Pocono Group in Maryland and West Virginia, and the upper part of the Pocono Formation is somet ...

and its lateral equivalent, the Burgoon Sandstone. Lessing, Dean, and Kulander (1992) mapped the Meadow Branch synclinorium in

Berkeley County, West Virginia Berkeley County is located in the Shenandoah Valley in the Eastern Panhandle region of West Virginia in the United States. The county is part of the Hagerstown- Martinsburg, MD- WV Metropolitan Statistical Area. As of the 2020 census, the co ...

, and noted that the Rockwell is approximately 200 meters thick here and that a 2-meter thick

diamictite Diamictite (; from Ancient Greek ''δια'' (dia-): ''through'' and ''µεικτός'' (meiktós): ''mixed'') is a type of lithified sedimentary rock that consists of nonsorted to poorly sorted terrigenous sediment containing particles that ra ...

is present near the base.Lessing, Peter, Dean, S.L., and Kulander, B.R., 1992, Stratigraphy and structure of Meadow Branch synclinorium, West Virginia: Southeastern Geology, v. 32, no. 3, p. 166-174.

References

{{Chronostratigraphy of Maryland Devonian System of North America Mississippian United States Sandstone formations of the United States Shale formations of the United States Devonian Maryland Devonian geology of Pennsylvania Devonian West Virginia Geologic formations of Maryland Geologic formations of Pennsylvania Geologic formations of West Virginia

Description

Stratigraphy

See also

References