Mauch Chunk Formation
Encyclopedia
The Mississippian Mauch Chunk Formation (Mmc) is a mapped bedrock unit in Pennsylvania
, Maryland
, and West Virginia
. It is named for the borough of Mauch Chunk, now known as Jim Thorpe, Pennsylvania
.
, siltstone
, sandstone
, and conglomerate
. The Loyalhanna Member is a local limestone and sandy limestone at its base, as well as the Greenbrier and Wymps Gap Members. Along the Allegheny Front
, the Loyalhanna is a greenish-gray, calcareous, cross bedded sandstone.
.
notably Adiantites have been identified. Some fish and worm burrows have also been observed.
atop many formations. Its upper contact is complex. In certain areas, the contact is conformable in others, there is an unconformity. However, the Pottsville Formation
is always above the Mauch Chunk.
was mined from the Mauch Chunk Formation near Jim Thorpe. (see Uranium mining in the United States
)
Pennsylvania
The Commonwealth of Pennsylvania is a U.S. state that is located in the Northeastern and Mid-Atlantic regions of the United States. The state borders Delaware and Maryland to the south, West Virginia to the southwest, Ohio to the west, New York and Ontario, Canada, to the north, and New Jersey to...
, Maryland
Maryland
Maryland is a U.S. state located in the Mid Atlantic region of the United States, bordering Virginia, West Virginia, and the District of Columbia to its south and west; Pennsylvania to its north; and Delaware to its east...
, and West Virginia
West Virginia
West Virginia is a state in the Appalachian and Southeastern regions of the United States, bordered by Virginia to the southeast, Kentucky to the southwest, Ohio to the northwest, Pennsylvania to the northeast and Maryland to the east...
. It is named for the borough of Mauch Chunk, now known as Jim Thorpe, Pennsylvania
Jim Thorpe, Pennsylvania
Jim Thorpe is a borough in Carbon County, Pennsylvania, USA. The population was 4,804 at the 2000 census. It is the county seat of Carbon County. The town has been called the "Switzerland of America" due to the picturesque scenery, mountainous location, and architecture; as well as the "Gateway to...
.
Description
The Mauch Chunk is defined as a grayish-red shaleShale
Shale is a fine-grained, clastic sedimentary rock composed of mud that is a mix of flakes of clay minerals and tiny fragments of other minerals, especially quartz and calcite. The ratio of clay to other minerals is variable. Shale is characterized by breaks along thin laminae or parallel layering...
, siltstone
Siltstone
Siltstone is a sedimentary rock which has a grain size in the silt range, finer than sandstone and coarser than claystones.- Description :As its name implies, it is primarily composed of silt sized particles, defined as grains 1/16 - 1/256 mm or 4 to 8 on the Krumbein phi scale...
, sandstone
Sandstone
Sandstone is a sedimentary rock composed mainly of sand-sized minerals or rock grains.Most sandstone is composed of quartz and/or feldspar because these are the most common minerals in the Earth's crust. Like sand, sandstone may be any colour, but the most common colours are tan, brown, yellow,...
, and conglomerate
Conglomerate (geology)
A conglomerate is a rock consisting of individual clasts within a finer-grained matrix that have become cemented together. Conglomerates are sedimentary rocks consisting of rounded fragments and are thus differentiated from breccias, which consist of angular clasts...
. The Loyalhanna Member is a local limestone and sandy limestone at its base, as well as the Greenbrier and Wymps Gap Members. Along the Allegheny Front
Allegheny Front
The Allegheny Front is the major southeast- or east-facing escarpment in the Allegheny Mountains in southern Pennsylvania, western Maryland, and eastern West Virginia, USA. The Allegheny Front delineates the Ridge-and-Valley Appalachians to its east from the Appalachian Plateau to its west...
, the Loyalhanna is a greenish-gray, calcareous, cross bedded sandstone.
Depositional environment
The early Mauch Chunk beds were deposited on a large basin receiving most of its sediments from distant highlands. Sea levels fluctuated and allowed some limestone deposition to occur early as well. Since the dominate color of the Mauch Chunk is red, much of the sediment was deposited above sea level in oxidizing conditions. The green colored members indicate a reducing environment characterized by frequent inundation by water either in a swamp, delta, or shallow sea. Later beds have frequent conglomerate beds signaling the first wave of the Alleghenian orogenyAlleghenian orogeny
The Alleghenian orogeny or Appalachian orogeny is one of the geological mountain-forming events that formed the Appalachian Mountains and Allegheny Mountains. The term and spelling Alleghany orogeny was originally proposed by H.P. Woodward in 1957....
.
Fossils
Plants from the division PteridospermatophytaPteridospermatophyta
The term Pteridospermatophyta refers to several distinct groups of extinct seed-bearing plants . The oldest fossil evidence of plants of this type is of late Devonian age, and they flourished particularly during the Carboniferous and Permian periods...
notably Adiantites have been identified. Some fish and worm burrows have also been observed.
Age
Relative age dating of the Mauch Chunk places it in the late Mississippian epoch, with some of the top layers in the early Pennsylvanian epoch, being deposited between 345 to 320(±3) million years ago. It rests conformablyUnconformity
An unconformity is a buried erosion surface separating two rock masses or strata of different ages, indicating that sediment deposition was not continuous. In general, the older layer was exposed to erosion for an interval of time before deposition of the younger, but the term is used to describe...
atop many formations. Its upper contact is complex. In certain areas, the contact is conformable in others, there is an unconformity. However, the Pottsville Formation
Pottsville Formation
The Pennsylvanian Pottsville Formation is a mapped bedrock unit in Pennsylvania, western Maryland, West Virginia, and Ohio. The formation is also recognized in Alabama. It is a major ridge-former In the Ridge-and-Valley Appalachians of the eastern United States...
is always above the Mauch Chunk.
Economic uses
In 1953, a small amount of uraniumUranium
Uranium is a silvery-white metallic chemical element in the actinide series of the periodic table, with atomic number 92. It is assigned the chemical symbol U. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons...
was mined from the Mauch Chunk Formation near Jim Thorpe. (see Uranium mining in the United States
Uranium mining in the United States
Uranium mining in the United States is the extraction of uranium-bearing ore from the earth. While uranium is used primarily for nuclear power, uranium mining had its roots in the production of uranium-bearing ore in 1898 with the mining of carnotite-bearing sandstones of the Colorado Plateau in...
)