Editing Geology of the Appalachians (section)

== Physiographic provinces==
The geographic boundaries of the Appalachian Mountains follow a definition that accounts for all the land mass in the United States and Canada used by the [[US Geological Survey]] and the Geologic Survey of Canada using the science of physiography. The US uses the term Appalachian Highlands, and Canada uses the term Appalachian Uplands, to define contiguous regions that have similar geology, topography, history, and native plant and animal communities. (The Appalachian Mountains are not synonymous with the [[Appalachian Plateau]], which is one of the provinces of the Appalachian Highlands).{{cn|date=December 2023}}

=== Appalachian Basin ===
The Appalachian Basin is a [[foreland basin]] containing Paleozoic [[sedimentary rock]]s of early [[Cambrian]] through early [[Permian]] age. From north to south, the Appalachian Basin province crosses [[New York (state)|New York]], [[Pennsylvania]], eastern [[Ohio]], [[West Virginia]], western [[Maryland]], eastern [[Kentucky]], western [[Virginia]], eastern [[Tennessee]], northwestern [[Georgia (U.S. state)|Georgia]], and northeastern [[Alabama]]. The northern end of the Appalachian Basin extends offshore into Lakes [[Lake Erie|Erie]] and [[Lake Ontario|Ontario]] as far as the United States–Canada border. The province covers an area of about {{convert|185500|mi2|km2}} and is {{convert|1075|mi|km}} long from northeast to southwest and between {{convert|20|and|310|mi|km|-1}} wide from northwest to southeast.<ref name="appBasin">{{USGS|url=http://certmapper.cr.usgs.gov/data/noga95/prov67/text/prov67.pdf|title=Appalachian Basin Province (067)|author=R.T. Ryder}}</ref>

The northwestern flank of the basin is a broad [[homocline]] that dips gently southeastward off the [[Cincinnati Arch]]. A complexly thrust faulted and folded [[terrane]] (Appalachian Fold and Thrust Belt or Eastern Overthrust Belt), formed at the end of the Paleozoic by the [[Alleghanian orogeny]], characterizes the eastern flank of the basin. Metamorphic and igneous rocks of the [[Blue Ridge Thrust Belt]] that bounds the eastern part of the Appalachian Basin Province were thrust westward more than {{convert|150|mi|km}} over lower Paleozoic sedimentary rocks.<ref name="appBasin" />

==== Coal, oil, and gas production ====
The Appalachian Basin is one of the most important [[coal]] producing regions in the U.S. and one of the largest in the world. [[Bituminous coal]] has been mined throughout the last three centuries. Currently, the coal primarily is used within the eastern U.S. or exported for [[Electricity generation|electrical power generation]], but some of it is suitable for [[metallurgy|metallurgical]] uses. Economically important coal beds were deposited primarily during Pennsylvanian time in a southeastward-thickening foreland basin. Coal and associated rocks form a [[Clastic rock|clastic]] wedge that thickens from north to south, from Pennsylvania into southeast West Virginia and southwestern Virginia.<ref name="coal">{{USGS|url=http://pubs.usgs.gov/pp/p1625c/CHAPTER_A/CHAPTER_A.pdf|title=Executive Summary—Coal Resource Assessment of Selected Coal Beds and Zones in the Northern and Central Appalachian Basin Coal Regions|author=Leslie F. Ruppert}}</ref>

Discovery of oil in 1859 in the [[Drake Well]], [[Venango County, Pennsylvania]], marked the beginning of the oil and gas industry in the Appalachian Basin. The discovery well opened a prolific trend of oil and gas fields, producing from upper [[Devonian]], [[Mississippian (geology)|Mississippian]], and Pennsylvanian [[sandstone]] reservoirs that extend from southern New York, across western Pennsylvania, central West Virginia, and eastern Ohio, to eastern Kentucky.<ref name="appBasin" />

A second major trend of oil and gas production in the Appalachian Basin began with the discovery in 1885 of oil and gas in lower [[Silurian]] Clinton sandstone reservoirs in [[Knox County, Ohio]]. By the late 1880s and early 1900s, the trend extended both north and south across east-central Ohio and included several counties in western New York where gas was discovered in lower Silurian Medina Group sandstones. About 1900, large oil reserves were discovered in Silurian and Devonian carbonate reservoirs in east-central Kentucky. Important gas discoveries from the lower Devonian Oriskany Sandstone in [[Guernsey County, Ohio]], in 1924; [[Schuyler County, New York]], in 1930; and [[Kanawha County, West Virginia]], in 1936 opened a major gas-producing trend across parts of New York, Pennsylvania, Maryland, Ohio, West Virginia, Kentucky, and Virginia.<ref name="appBasin" /> Another drilling boom occurred in the 1960s in [[Morrow County, Ohio]], where oil was discovered in the Upper Cambrian part of the Knox [[Dolomite (rock)|Dolomite]].<ref name="appBasin" />

=== Crystalline Appalachians ===
[[File:Mid-Atlantic Appalachian rock types.gif|thumb|upright=2|Geological map of the southern Crystalline Appalachians]]
The Blue Ridge, Piedmont, Adirondack, and New England Provinces are collectively known as the Crystalline Appalachians because they consist of Precambrian and Cambrian igneous and metamorphic rocks.<ref name="nyc">{{cite web |title=The Sedimentary Appalachians |work=NYC Regional Geology |url=http://3dparks.wr.usgs.gov/nyc/valleyandridge/sedimentaryapp.htm |archive-url=https://web.archive.org/web/20110516070439/http://3dparks.wr.usgs.gov/nyc/valleyandridge/sedimentaryapp.htm |archive-date=May 16, 2011 |access-date=May 20, 2010 |url-status=dead }}</ref>

The Blue Ridge Thrust Belt Province underlies parts of eight states from central Alabama to southern Pennsylvania. Along its western margin, the Blue Ridge is thrust over the folded and faulted margin of the Appalachian basin, so that a broad segment of [[Paleozoic]] strata extends eastward for tens of miles, buried beneath these subhorizontal crystalline thrust sheets.<ref>{{cite journal|last1=Harris|first1=L.D.|last2=Harris|first2=A.G.|last3=de Witt, Jr.|first3=W.|last4=Bayer|first4=K.C.|year=1981|title=Evaluation of the southern eastern overthrust belt beneath Blue Ridge-Piedmont thrust|journal=American Association of Petroleum Geologists Bulletin|volume=65|issue=12|pages=2497–2505|doi=10.1306/03b599ef-16d1-11d7-8645000102c1865d}}</ref> At the surface, the Blue Ridge consists of a mountainous to hilly region, the main component of which are the Blue Ridge Mountains that extend from Georgia to Pennsylvania. Surface rocks consist mainly of a core of moderate-to high-rank crystalline metamorphic or igneous rocks which, because of their superior resistance to weathering and erosion, commonly rise above the adjacent areas of low-grade metamorphic and sedimentary rock. The province is bounded on the north and west by the Paleozoic strata of the Appalachian Basin and on the south by Cretaceous and younger sedimentary rocks of the [[Gulf Coastal Plain]]. It is bounded on the east by metamorphic and sedimentary rocks of the [[Piedmont (United States)|Piedmont Province]].<ref name="otherProv">{{USGS|title=Blue Ridge Thrust Belt (068), Piedmont Province (069), Atlantic Coastal Plain Province (070), Adirondack Province (071), and New England Province (072)|url=http://certmapper.cr.usgs.gov/data/noga95/prov71/text/prov71.pdf|author=Robert C. Milici}}</ref>

The Adirondack and New England Provinces include sedimentary, meta-sedimentary, and [[Intrusive rock|plutonic]] igneous rocks, mainly of Cambrian and Ordovician age, similar [[lithologically]] to rocks in the Blue Ridge and Piedmont Provinces to the south. The uplifted, nearly-circular Adirondack Mountains consist of a core of ancient Precambrian rocks that are surrounded by upturned Cambrian and Ordovician sedimentary rocks.<ref name="otherProv" />