page_title: Marcellus Formation
section_title: Geomorphological expression
hierarchical_section_title: Marcellus Formation / Geomorphological expression
caption_attribution_description: English: Portion of global paleogeographic reconstruction of the Earth in the middle Devonian period 385 million years ago, showing Eastern North America with key features labeled
context_page_description: The Marcellus Formation or the Marcellus Shale is a Middle Devonian age unit of sedimentary rock found in eastern North America. Named for a distinctive outcrop near the village of Marcellus, New York, in the United States,
  it extends throughout much of the Appalachian Basin.
  The unit name usage by the U.S. Geological Survey includes Marcellus Shale and Marcellus Formation. The term "Marcellus Shale" is the preferred name throughout most of the Appalachian region, although the term "Marcellus Formation" is also acceptable within the State of Pennsylvania. The unit was first described and named as the "Marcellus shales" by J. Hall in 1839.
context_section_description: Upturned beds are exposed in sections of the folded Ridge-and-Valley Appalachians, including exposures on the flanks and axis of the Broad Top Synclinorium in south central Pennsylvania. Exposed beds are nearly horizontal on the Allegheny Plateau, but upturned to form slightly overturned beds found along the Allegheny Front.
  From Wind Gap, Pennsylvania heading south, the dip of the beds steepens, becoming vertical at Bowmanstown on the Lehigh River. Nearby, in the Lehigh Gap area of Pennsylvania, the Marcellus is extensively faulted,
  and the beds are steeply overturned, with a reverse dip angle of up to 40° south.
  The Marcellus Shale and the fine-grained shales near the middle of the Mahantango Formation are classified by geologists as slope-formers.
  Marcellus and Mahantango shale beds dipping at 60° to 75° to the west form the west facing slopes of Tonoloway Ridge on the west flank of the Cacapon Mountain anticline in the Eastern Panhandle of West Virginia.
  On the eastern limb of this anticline, beds of these shales  dipping to the east at a shallower angle also form the steep slopes on the east side of Warm Springs Ridge.
  The Marcellus is easily eroded, and is also found underlying low areas between some Appalachian ridges, forming linear valleys of moderate relief. These bedrock surfaces are typically covered with colluvium from erosion of stratigraphically higher and more erosion-resistant strata that form the surrounding higher ground. The soils formed from the Marcellus and the overlying Hamilton shales are deep, free of stones, and well suited for agriculture.
  Sampling of soil formed on the Marcellus bedrock showed the dominant mineralogy consisted of quartz, illite, montmorillonite, muscovite, and biotite, with phases of todorokite and trona appearing at depths closer to the bedrock.
  Upturned beds of the soft shale also capture streams and rivers with relatively straight segments in strike valleys such as the Aquashicola Creek and McMichael Creek at the foot of The Poconos,
  and the long, straight section of the Lost River in West Virginia.
  Below Port Jervis, New York, the Walpack Ridge deflects the Delaware River into the Minisink Valley, where it follows the southwest strike of the eroded Marcellus beds along the Pennsylvania – New Jersey state line for 40 km (25 mi) to the end of the ridge at Walpack Bend in the Delaware Water Gap National Recreation Area.
  The Minisink is a buried valley where the Delaware flows in a bed of glacial till that buried the eroded Marcellus bedrock during the last glacial period. This buried valley continues along the strike of the Marcellus southwest from the bend through Stroudsburg, Pennsylvania, and northeast from Port Jervis toward the Hudson River,
  along the route of the Delaware and Hudson Canal.
caption: Paleogeographic reconstruction of the Appalachian Basin area during deposition of the Marcellus[43]
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