Related Research Articles
The geology of the Appalachians dates back more than 1.2 billion years to the Mesoproterozoic era when two continental cratons collided to form the supercontinent Rodinia, 500 million years prior to the development of the range during the formation of Pangea. The rocks exposed in today's Appalachian Mountains reveal elongate belts of folded and thrust faulted marine sedimentary rocks, volcanic rocks, and slivers of ancient ocean floor—strong evidences that these rocks were deformed during plate collision. The birth of the Appalachian ranges marks the first of several mountain building plate collisions that culminated in the construction of Pangea with the Appalachians and neighboring Anti-Atlas mountains near the center. These mountain ranges likely once reached elevations similar to those of the Alps and the Rocky Mountains before they were eroded.
The Big Clifty Sandstone is a geologic formation in Illinois and Kentucky. It is a subunit of the Golconda Formation in Kentucky and is correlative with the Fraileys Shale to which it grades to in southern Illinois. The Big Clifty and Golconda are part of the Chesterian Series of late Mississippian age. The Big Clifty Sandstone was deposited in deltaic to marginal marine environment by the paleo Michigan River which in modern directions flowed south from the Canadian shield, the sediment source, and then westward depositing sediment across Illinois, Kentucky, and Indiana, as the Big Clifty Formation of the Stephensport Group. At Mammoth Cave National Park the Big Clifty overlies the Girkin Formation, the uppermost of three cave forming carbonate formations which the Mammoth-Flint Ridge cave system spans. Below the Girkin Formation are the Ste. Genevieve Limestone, and the St. Louis Limestone respectively. The chemically resistant sediments comprising the Big Clifty, and similar siliciclastics, act as a caprock over the dissolving carbonates. The presence of the Big Clifty is one of several contributory factors that create favorable conditions for the formation, and subsequent preservation, of connected cavernous porosity in the Mammoth-Flint Ridge cave system.
The U.S. state of Georgia is commonly divided into four geologic regions that influence the location of the state's four traditional physiographic regions. The four geologic regions include the Appalachian foreland, Blue Ridge, Piedmont, and Coastal Plain. These four geologic regions commonly share names with and typically overlap the four physiographic regions of the state: the Appalachian Plateau and adjacent Valley and Ridge; the Blue Ridge; the Piedmont and the Coastal Plain.
The Ordovician Martinsburg Formation (Om) is a mapped bedrock unit in Pennsylvania, New Jersey, Maryland, Virginia, and West Virginia. It is named for the town of Martinsburg, West Virginia for which it was first described. It is the dominant rock formation of the Great Appalachian Valley in New Jersey and Pennsylvania.
The Silurian Tuscarora Formation — also known as Tuscarora Sandstone or Tuscarora Quartzite — is a mapped bedrock unit in Pennsylvania, Maryland, West Virginia, and Virginia, US.
The Ordovician Reedsville Formation is a mapped surficial bedrock unit in Pennsylvania, Maryland, Virginia, West Virginia, and Tennessee, that extends into the subsurface of Ohio. This rock is a slope-former adjacent to the prominent ridge-forming Bald Eagle sandstone unit in the Appalachian Mountains. It is often abbreviated Or on geologic maps.
The Hamilton Group is a Devonian-age geological group which is located in the Appalachian region of the United States. It is present in New York, Pennsylvania, Maryland, Ohio, West Virginia, northwestern Virginia and Ontario, Canada, and is mainly composed of marine shale with some sandstone.
The Devonian Mahantango Formation is a mapped bedrock unit in Pennsylvania, West Virginia, and Maryland. It is named for the North branch of the Mahantango Creek in Perry and Juniata counties in Pennsylvania. It is a member of the Hamilton Group, along with the underlying the Marcellus Formation Shale. South of Tuscarora Mountain in south central Pennsylvania, the lower members of this unit were also mapped as the Montebello Formation. Details of the type section and of stratigraphic nomenclature for this unit as used by the U.S. Geological Survey are available on-line at the National Geologic Map Database.
The Pennsylvanian Pottsville Formation is a mapped bedrock unit in Pennsylvania, western Maryland, West Virginia, Ohio, and Alabama. It is a major ridge-former in the Ridge-and-Valley Appalachians of the eastern United States. The Pottsville Formation is conspicuous at many sites along the Allegheny Front, the eastern escarpment of the Allegheny or Appalachian Plateau.
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 Ridgeley sandstone is a sandstone or quartzite of Devonian age found in the Appalachian Mountains of Pennsylvania, Maryland, West Virginia, and Virginia, United States. The Ridgeley is fine-grained, siliceous, calcareous in its lower strata, sometimes fossiliferous, and sometimes locally pebbly or conglomeritic. Varying in thickness from 12 to 500 feet, this rock slowly erodes into white quartz sand that often washes or blows away, but sometimes accumulates at large outcrops. When freshly broken, the rock is white, but outcrop surfaces are often stained yellowish by iron oxides.
The Shady Dolomite is a geologic formation composed of marine sedimentary rocks of early Cambrian age. It outcrops along the eastern margin of the Blue Ridge province in the southeastern United States and can be found in outcrops in the states of Alabama, Georgia, Tennessee, North Carolina, and Virginia. It can also be found in the subsurface of Kentucky, Ohio, and West Virginia. The Shady is predominantly composed of dolomite and limestone with lesser amounts of mudrock. It contains fossils of trilobites, archaeocyathids, algae, brachiopods, and echinoderms, along with the enigmatic fossil Salterella. The Shady Dolomite was first described by Arthur Keith in 1903 and was named for exposures in the Shady Valley of Johnson County in the state of Tennessee. Near Austinville, Virginia, the Shady hosts ore deposits that have been mined extensively for lead and zinc ore.
The Tomstown Dolomite or Tomstown Formation is a geologic formation in Maryland, Pennsylvania, Virginia and West Virginia. It preserves fossils dating to the Cambrian Period.
The Antietam Formation or Antietam Sandstone is a geologic formation in Pennsylvania, Maryland and West Virginia. It is largely quartz sandstone with some quartzite and quartz schist. It preserves Skolithos trace fossils dating back to the Cambrian Period.
The Harpers Formation is a geologic formation in Maryland, Pennsylvania, Virginia, and West Virginia, consisting of schist, phyllite, and shale. It dates back to the early Cambrian period. It is considered part of the Chilhowee Group.
The Weverton Formation is a quartzite geologic formation in Maryland, Virginia, West Virginia, and Pennsylvania. It is considered the basal member of the Chilhowee Group. The Weverton Formation dates back to the Cambrian period.
The Catoctin Formation is a geologic formation that expands through Virginia, Maryland, and Pennsylvania. It dates back to the Precambrian and is closely associated with the Harpers Formation, Weverton Formation, and the Loudoun Formation. The Catoctin Formation lies over a granitic basement rock and below the Chilhowee Group making it only exposed on the outer parts of the Blue Ridge. The Catoctin Formation contains metabasalt, metarhyolite, and porphyritic rocks, columnar jointing, low-dipping primary joints, amygdules, sedimentary dikes, and flow breccias. Evidence for past volcanic activity includes columnar basalts and greenstone dikes.
The Huntersville Chert or Huntersville Formation is a Devonian geologic formation in the Appalachian region of the United States. It is primarily composed of mottled white, yellow, and dark grey chert, and is separated from the underlying Oriskany Sandstone by an unconformity. The Huntersville Chert is laterally equivalent to the Needmore Shale, which lies north of the New River. It is also laterally equivalent to a sandy limestone unit which is often equated with the Onondaga Limestone. to the west and the Needmore Shale to the east. These formations are placed in the Onesquethaw Stage of Appalachian chronostratigraphy, roughly equivalent to the Emsian and Eifelian stages of the broader Devonian system.
The geology of Virginia began to form 1.8 billion years ago and potentially even earlier. The oldest rocks in the state were metamorphosed during the Grenville orogeny, a mountain building event beginning 1.2 billion years ago in the Proterozoic, which obscured older rocks. Throughout the Proterozoic and Paleozoic, Virginia experienced igneous intrusions, carbonate and sandstone deposition, and a series of other mountain building events which defined the terrain of the inland parts of the state. The closing of the Iapetus Ocean, to form the supercontinent Pangaea added additional small landmasses, some of which are now hidden beneath thick Atlantic Coastal Plain sediments. The region subsequently experienced the rifting open of the Atlantic Ocean in the Mesozoic, the development of the Coastal Plain, isolated volcanism and a series of marine transgressions that flooded much of the area. Virginia has extensive coal, deposits of oil and natural gas, as well as deposits of other minerals and metals, including vermiculite, kyanite and uranium.
The Catharpin Creek Formation is a Late Triassic geologic formation in Maryland and Virginia. It is found along the western edge of the Culpeper Basin, one of the largest sedimentary basins in the Newark Supergroup. Compared to the underlying Bull Run Formation, the Catharpin Creek Formation is dominated by much coarser sedimentary rocks such as sandstone and conglomerate. The base of the formation is reddish arkosic sandstone, which grades into drabber thin-bedded siltstone and shale in cyclical sequences.
References
- ↑ Scott Southworth; David K. Brezinski (1996). "Geology of the Harpers Ferry Quadrangle, Virginia, Maryland, and West Virginia" (PDF). U.S. Geological Survey Bulletin. 2123. doi:10.3133/B2123. ISSN 8755-531X. Wikidata Q61462697.
- ↑ C. Erwin Brown; Gertrude C. Gazdik (1982). "Mineral resource potential map of the James River Face Wilderness, Bedford and Rockbridge counties, Virginia" (PDF). Miscellaneous Field Studies Map. 1337D. doi:10.3133/MF1337D. Wikidata Q62120774.
- ↑ "Geolex - Weisner publications". Geolex Geologic Names Database. U.S. Geological Survey. 1890–1991. Retrieved April 3, 2024.
- ↑ "Geolex - Wilson Ridge publications". Geolex Geologic Names Database. U.S. Geological Survey. 1980–1988. Retrieved April 3, 2024.
 | This article about a specific stratigraphic formation in the United States is a stub. You can help Wikipedia by expanding it. |