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 Acadian orogeny is a long-lasting mountain building event which began in the Middle Devonian, reaching a climax in the Late Devonian. It was active for approximately 50 million years, beginning roughly around 375 million years ago (Ma), with deformational, plutonic, and metamorphic events extending into the early Mississippian. The Acadian orogeny is the third of the four orogenies that formed the Appalachian Mountains and subsequent basin. The preceding orogenies consisted of the Grenville and Taconic orogenies, which followed a rift/drift stage in the Neoproterozoic. The Acadian orogeny involved the collision of a series of Avalonian continental fragments with the Laurasian continent. Geographically, the Acadian orogeny extended from the Canadian Maritime provinces migrating in a southwesterly direction toward Alabama. However, the northern Appalachian region, from New England northeastward into Gaspé region of Canada, was the most greatly affected region by the collision.
The Taconic orogeny was a mountain building period that ended 440 million years ago (Ma) and affected most of modern-day New England. A great mountain chain formed from eastern Canada down through what is now the Piedmont of the east coast of the United States. As the mountain chain eroded in the Silurian and Devonian periods, sediment spread throughout the present-day Appalachians and midcontinental North America.
The geology of Illinois includes extensive deposits of marine sedimentary rocks from the Palaeozoic, as well as relatively minor contributions from the Mesozoic and Cenozoic. Ice age glaciation left a wealth of glacial topographic features throughout the state.
The Michigan Basin is a geologic basin centered on the Lower Peninsula of the U.S. state of Michigan. The feature is represented by a nearly circular pattern of geologic sedimentary strata in the area with a nearly uniform structural dip toward the center of the peninsula.
The Geology of Pennsylvania consists of six distinct physiographic provinces, three of which are subdivided into different sections. Each province has its own economic advantages and geologic hazards and plays an important role in shaping everyday life in the state. From the southeast corner to the northwest corner of the state, they include: the Atlantic Plain Province, the Piedmont Province, the New England Province, the Ridge and Valley Province, the Appalachain Province, and the Central Lowlands Province.
West Virginia's geologic history stretches back into the Precambrian, and includes several periods of mountain building and erosion. At times, much of what is now West Virginia was covered by swamps, marshlands, and shallow seas, accounting for the wide variety of sedimentary rocks found in the state, as well as its wealth of coal and natural gas deposits. West Virginia has had no active volcanism for hundreds of millions of years, and does not experience large earthquakes, although smaller tremors are associated with the Rome Trough, which passes through the western part of the state.
The Cincinnati Arch is a broad structural uplift between the Illinois Basin to the west, the Michigan Basin to the northwest, and the Appalachian Basin and Black Warrior Basin to the east and southeast. It existed as a positive topographic area during late Ordovician through the Devonian period which stretched from northern Alabama northeastward to the southeastern tip of Ontario. Fossils from the Ordovician are commonplace in the geologic formations which make up the Cincinnati Arch and are commonly studied along man made roadcuts. The Nashville Dome of Tennessee and the Jessamine Dome or Lexington Dome of central Kentucky make up the central portion of the arch. In the northern part, north of Cincinnati, Ohio, the Cincinnati Arch branches to form the Findlay and Kankakee arches. The Findlay plunges under Ontario and reappears as the Algonquin Arch further north.
The Iapetus Suture is one of several major geological faults caused by the collision of several ancient land masses forming a suture. It represents in part the remains of what was once the Iapetus Ocean. Iapetus was the father of Atlas in Greek mythology, making his an appropriate name for what used to be called the 'Proto-Atlantic Ocean'. When the Atlantic Ocean opened, in the Cretaceous period, it took a slightly different line from that of the Iapetus suture, with some originally Laurentian rocks being left behind in north-west Europe and other, Avalonian, rocks remaining as part of Newfoundland.
The Queenston Formation is a geological formation of Upper Ordovician age, which outcrops in Ontario, Canada and New York, United States. A typical outcrop of the formation is exposed at Bronte Creek just south of the Queen Elizabeth Way. The formation is a part of the Queenston Delta clastic wedge, formed as an erosional response to the Taconic Orogeny. Lithologically, the formation is dominated by red and grey shales with thin siltstone, limestone and sandstone interlayers. As materials, comprising the clastic wedge, become coarser in close proximity to the Taconic source rocks, siltstone and sandstone layers are predominant in New York.
The Lexington Limestone is a prominent geologic formation that constitutes a large part of the late Ordovician bedrock of the inner Bluegrass region in Kentucky. Named after the city of Lexington, the geologic formation has heavily influenced both the surface topography and economy of the region.
The Mansfield Natural Gas Field is located west of Mansfield, Ohio, within the Appalachian foreland basin. The field is 1.5 miles (2.4 km) long by 1.4 miles (2.3 km) wide and is in a general oval shape, stretching northward. This field, although small, is an analog for many of the natural gas fields that occur within the Appalachian Basin. It was first discovered by the Pan American Petroleum and Transport Company in the early 1930s. It is part of the Utica – Lower Paleozoic system, which is estimated to make up 15 to 20 percent of the total hydrocarbon abundance of the Appalachian Basin.
The Precordillera terrane of western Argentina is a large mountain range located southeast of the main Andes mountain range. The evolution of the Precordillera is noted for its unique formation history compared to the region nearby. The Cambrian-Ordovian sedimentology in the Precordillera terrane has its source neither from old Andes nor nearby country rock, but shares similar characteristics with the Grenville orogeny of eastern North America. This indicates a rift-drift history of the Precordillera in the early Paleozoic. The Precordillera is a moving micro-continent which started from the southeast part of the ancient continent Laurentia. The separation of the Precordillera started around the early Cambrian. The mass collided with Gondwana around Late Ordovician period. Different models and thinking of rift-drift process and the time of occurrence have been proposed. This page focuses on the evidence of drifting found in the stratigraphical record of the Precordillera, as well as exhibiting models of how the Precordillera drifted to Gondwana.
The geology of Virginia began to form at least 1.8 billion years ago. 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 formed the supercontinent Pangaea, and created 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 deposits of coal, oil, and natural gas, as well as deposits of other minerals and metals, including vermiculite, kyanite and uranium.
The geology of Ohio formed beginning more than one billion years ago in the Proterozoic eon of the Precambrian. The igneous and metamorphic crystalline basement rock is poorly understood except through deep boreholes and does not outcrop at the surface. The basement rock is divided between the Grenville Province and Superior Province. When the Grenville Province crust collided with Proto-North America, it launched the Grenville orogeny, a major mountain building event. The Grenville mountains eroded, filling in rift basins and Ohio was flooded and periodically exposed as dry land throughout the Paleozoic. In addition to marine carbonates such as limestone and dolomite, large deposits of shale and sandstone formed as subsequent mountain building events such as the Taconic orogeny and Acadian orogeny led to additional sediment deposition. Ohio transitioned to dryland conditions in the Pennsylvanian, forming large coal swamps and the region has been dryland ever since. Until the Pleistocene glaciations erased these features, the landscape was cut with deep stream valleys, which scoured away hundreds of meters of rock leaving little trace of geologic history in the Mesozoic and Cenozoic.
The geology of Kentucky formed beginning more than one billion years ago, in the Proterozoic eon of the Precambrian. The oldest igneous and metamorphic crystalline basement rock is part of the Grenville Province, a small continent that collided with the early North American continent. The beginning of the Paleozoic is poorly attested and the oldest rocks in Kentucky, outcropping at the surface, are from the Ordovician. Throughout the Paleozoic, shallow seas covered the area, depositing marine sedimentary rocks such as limestone, dolomite and shale, as well as large numbers of fossils. By the Mississippian and the Pennsylvanian, massive coal swamps formed and generated the two large coal fields and the oil and gas which have played an important role in the state's economy. With interludes of terrestrial conditions, shallow marine conditions persisted throughout the Mesozoic and well into the Cenozoic. Unlike neighboring states, Kentucky was not significantly impacted by the Pleistocene glaciations. The state has extensive natural resources, including coal, oil and gas, sand, clay, fluorspar, limestone, dolomite and gravel. Kentucky is unique as the first state to be fully geologically mapped.
The Durness Group is a geological group, a carbonate-dominated stratigraphic unit that forms a c. 170 km long narrow and discontinuous outcrop belt along the north-western coast of Scotland from the Isle of Skye and Loch Kishorn in the south to Durness and Loch Eriboll in the north. It forms the youngest part of the foreland basin of the Moine Thrust Belt in the Scottish Northwest Highlands and is incorporated into this belt's lowermost thrust sheets, where it is often affected by thrust faulting. It overlies the Ardvreck Group.
The Grampian orogeny was an orogeny that affected Scotland in the middle of the Ordovician. At the time, Scotland was part of proto-North American continent Laurentia.
The Cayugan Series contains a number of carbonate, shale and evaporite formations of the upper Silurian System of sedimentary strata in eastern North America. It was formed during a period of marine transgression, and is near the end of the placid shallow marine environments of the Cambrian through Ordovician periods. The end of the Taconic orogeny marks the beginning of the Cayugan. A number of changes were taking place as the Iapetus Ocean was slowly shrinking. The north end of the sea had already closed. At the end of the Silurian and of the Cayugan Series, the Iapetus Ocean had entirely closed, leaving behind the Iapetus Suture. A result of being closed at one end was that fluctuations in sea level allowed for large parts of the Appalachian and Michigan basins to form large evaporite deposits. All of these deposits are found with in the Salina Group. While the Salina covers an area from New York to Illinois south into Kentucky and Tennessee, the evaporites are primarily found in western New York, western and central Pennsylvania, eastern Ohio and north western West Virginia. As well as in the Michigan Basin.
The Knox Supergroup, also known as the Knox Group and the Knox Formation, is a widespread geologic group in the Southeastern United States. The age is from the Late Cambrian to the Early Ordovician. Predominantly, it is composed of carbonates, chiefly dolomite, with some limestone. There are also cherty inclusions as well as thin beds of sandstone.
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