imported>Volcanoguy: removed Category:Conglomerate formations; added Category:Conglomerate formations of the United States using HotCat

2025-06-20T19:22:24Z

removed Category:Conglomerate formations; added Category:Conglomerate formations of the United States using HotCat

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{{Short description|Mapped bedrock unit}}
{{Infobox rockunit
| name = Mauch Chunk Formation
| image =
| caption =
| type = [[Formation (stratigraphy)|Formation]]
| age = [[Mississippian (geology)|Mississippian]]
| period = Mississippian
| prilithology =
| otherlithology =
| namedfor =
| namedby =
| region = Maryland, Pennsylvania, West Virginia,
| country = United States
| coordinates =
| unitof =
| subunits =
| underlies = [[Pottsville Formation]]
| overlies = [[Pocono Formation]]
| thickness =
| extent =
| area =
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}}

The [[Mississippian age|Mississippian]] '''Mauch Chunk Formation''' is a mapped bedrock unit in [[Pennsylvania]], [[Maryland]], and [[West Virginia]]. It is named for the township of Mauch Chunk, now known as borough of [[Jim Thorpe, Pennsylvania]] and for nearby Mauch Chunk Ridge where the formation crops out.

==Description==
The Mauch Chunk is defined as a grayish-red [[shale]], [[siltstone]], [[sandstone]], and [[conglomerate (geology)|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.<ref>Berg, T.M., Edmunds, W.E., Geyer, A.R. and others, compilers, (1980). Geologic Map of Pennsylvania: Pennsylvania Geologic Survey, Map 1, scale 1:250,000.</ref>

A notable exposure of the Loyalhanna Member is [[Laurel Caverns]] in [[Fayette County, Pennsylvania|Fayette County]].

===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 dominant 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 in a swamp, delta, or shallow sea. Later beds have frequent conglomerate beds signaling the first wave of the [[Alleghenian orogeny]].<ref>Wood, G.H., Trexler, J.P., Kehn, T.M., (1964). Geology of the West-Central Part of the Southern Anthracite Field and Adjoining Areas, Pennsylvania. United States Geological Survey, C-46.</ref>

===Fossils===
Plants from the division [[Pteridospermatophyta]] notably [[Adiantites]] have been identified. Some fish and worm burrows have also been observed.<ref>Jennings, J.R., (1985). Fossil plants from the Mauch Chunk Formation of Pennsylvania: Morphology of Adiantites Antiquus. Journal of Paleontology, v 59 n 5, p 1146-1157.</ref>

==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 and 320(±3) million years ago. It rests [[unconformity|conformably]] 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.<ref>Berg, T.M., et al., (1983). Stratigraphic Correlation Chart of Pennsylvania: G75, Pennsylvania Geologic Survey, Harrisburg, Pennsylvania.</ref>

==Economic uses==
In 1953, a small amount of [[uranium]] was mined from the Mauch Chunk Formation near Jim Thorpe. (see [[Uranium mining in the United States]])

==References==
<references/>

== See also ==
* [[Ridge-and-Valley Appalachians]]
* [[Geology of Pennsylvania]]
* [[Canaan Valley]]

{{Chronostratigraphy of Maryland}}

[[Category:Sandstone formations of the United States]]
[[Category:Shale formations of the United States]]
[[Category:Siltstone formations of the United States]]
[[Category:Conglomerate formations of the United States]]
[[Category:Carboniferous Maryland]]
[[Category:Carboniferous geology of Pennsylvania]]
[[Category:Carboniferous West Virginia]]
[[Category:Mississippian United States]]
[[Category:Appalachian Mountains|~]]
[[Category:Geologic formations of Maryland]]
[[Category:Geologic formations of Pennsylvania]]
[[Category:Geologic formations of West Virginia]]
[[Category:Carboniferous southern paleotropical deposits]]

Mauch Chunk Formation - Revision history

imported>Volcanoguy: removed Category:Conglomerate formations; added Category:Conglomerate formations of the United States using HotCat