When did the mountain building period that created the Taconic unconformity end?
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Taconic unconformity The Taconic unconformity is a major unconformity created during the Taconic orogeny, exposed from eastern New York State to the Gaspe peninsula. The orogeny was a long one that comprised multiple bursts; it primarily dated to the end of the Ordovician, and the underlying rocks are primarily this age. It is overlain by Silurian and Devonian metasediments.
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Taconic orogeny The Taconic orogeny was a mountain building period that ended 440 million years ago and affected most of modern-day New England. A great mountain chain formed from eastern Canada down through what is now the Piedmont off the East coast of the United States. As the mountain chain eroded in the Silurian and Devonian periods, sediments from the mountain chain spread throughout the present-day Appalachians and midcontinental North America.
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Armorican terrane The Armorican terrane, Armorican terrane assemblage, or simply Armorica, was a microcontinent or group of continental fragments that rifted away from Gondwana towards the end of the Silurian and collided with Laurussia towards the end of the Carboniferous during the Variscan orogeny. The name is taken from Armorica, the Gaulish name for a large part of northwestern France that includes Brittany, as this matches closely to the present location of the rock units that form the main part of this terrane.
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Ice age An ice age is a period of long-term reduction in the temperature of Earth's surface and atmosphere, resulting in the presence or expansion of continental and polar ice sheets and alpine glaciers. Within a long-term ice age, individual pulses of cold climate are termed "glacial periods" (or alternatively "glacials" or "glaciations" or colloquially as "ice age"), and intermittent warm periods are called "interglacials". In the terminology of glaciology, "ice age" implies the presence of extensive ice sheets in both northern and southern hemispheres. By this definition, we are in an interglacial period—the Holocene—of the ice age. The ice age began 2.6 million years ago at the start of the Pleistocene epoch, because the Greenland, Arctic, and Antarctic ice sheets still exist.
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Supercontinent cycle The supercontinent cycle is the quasi-periodic aggregation and dispersal of Earth's continental crust. There are varying opinions as to whether the amount of continental crust is increasing, decreasing, or staying about the same, but it is agreed that the Earth's crust is constantly being reconfigured. One complete supercontinent cycle is said to take 300 to 500 million years. Continental collision makes fewer and larger continents while rifting makes more and smaller continents.
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Hawaii hotspot The Hawaii hotspot is a volcanic hotspot located near the namesake Hawaiian Islands, in the northern Pacific Ocean. One of the most well-known and heavily studied hotspots in the world, the Hawaii plume is responsible for the creation of the Hawaiian – Emperor seamount chain, a chain of volcanoes over 5,800 kilometres (3,600 mi) long. Four of these volcanoes are active, two are dormant, and more than 123 are extinct, many having since been ground beneath the waves by erosion as seamounts and atolls. The chain extends from south of the island of Hawaiʻ i to the edge of the Aleutian Trench, near the eastern edge of Russia. While most volcanoes are created by geological activity at tectonic plate boundaries, the Hawaii hotspot is located far from plate boundaries. The classic hotspot theory, first proposed in 1963 by John Tuzo Wilson, proposes that a single, fixed mantle plume builds volcanoes that then, cut off from their source by the movement of the Pacific Plate, become increasingly inactive and eventually erode below sea level over millions of years. According to this theory, the nearly 60° bend where the Emperor and Hawaiian segments of the chain meet was caused by a sudden shift in the movement of the Pacific Plate. In 2003, fresh investigations of this irregularity led to the proposal of a mobile hotspot theory, suggesting that hotspots are mobile, not fixed, and that the 47-million-year-old bend was caused by a shift in the hotspot's motion rather than the plate's.
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Hangenberg event The Hangenberg event is a bioevent that occurred at the end of the Famennian epoch (late Devonian) associated with the Late Devonian extinction (roughly 358.9 ± 0.4 million years ago); it was an anoxic event marked by a black shale. It has been proposed that this was related to a rapid sea-level fall due to the last phase of the Devonian Southern Hemisphere glaciation. It has also been suggested that it was linked to an increase in terrestrial plant cover, leading to increased nutrient supply in rivers. This may have led to eutrophication of semi-restricted epicontinental seas and could have stimulated algal blooms.
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Bridge River Ocean The Bridge River Ocean was an ancient ocean that existed between North America and the Insular Islands during the Paleozoic time. Like the earlier Slide Mountain Ocean, the Bridge River Ocean had a subduction zone on the ocean floor called the Insular Trench. The closure of the Bridge River Ocean occurred about 115 million years ago, during the mid Cretaceous period.
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European Cenozoic Rift System The European Cenozoic Rift System (ECRIS) is an 1100 km long system of rifts formed in the foreland of the Alps as the lithosphere responded to the effects of the Alpine and Pyrenean orogenies. The system began to form during the Late Eocene and parts, particularly the Upper and Lower Rhine Grabens, remain seismically active today and are responsible for most of the larger earthquakes in Europe, north of the Alps.
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Eocene Thermal Maximum 2 Eocene Thermal Maximum 2 (ETM-2), also called H-1 or the Elmo (Eocene Layer of Mysterious Origin) event, was a transient period of global warming that occurred approximately 53.7 million years ago (Ma). It appears to be the second major hyperthermal that punctuated the long-term warming trend from the Late Paleocene through the early Eocene (58 to 50 Ma).
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Timeline of Carboniferous research This timeline of Carboniferous research is a chronological listing of events in the history of geology and paleontology focused on the study of earth during the span of time lasting from 358.9–298.9 million years ago and the legacies of this period in the rock and fossil records.
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Geosyncline Geosyncline is a geological concept which was developed in the late 19th and early 20th centuries before the concept of plate tectonics was developed. A geosyncline was described as a subsiding linear trough that was caused by the accumulation of sedimentary rock strata deposited in a basin and subsequently compressed, deformed, and uplifted into a mountain range, with attendant volcanism and plutonism. The filling of a geosyncline with sediment is accompanied in the late stages of deposition by folding, crumpling, and faulting of the deposits. Intrusion of crystalline igneous rock and regional uplift along the axis of the trough generally complete the history of a particular geosyncline. It is then transformed into a belt of folded mountains. Thick volcanic sequences, together with greywackes (sandstones rich in rock fragments with a muddy matrix), cherts, and various sediments reflecting deepwater deposition or processes, were considered "eugeosynclinal" deposits of the outer deepwater segment of geosynclines.
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Pliocene The Pliocene ( ; also Pleiocene ) Epoch is the epoch in the geologic timescale that extends from 5.333 million to 2.58 million years BP. It is the second and youngest epoch of the Neogene Period in the Cenozoic Era. The Pliocene follows the Miocene Epoch and is followed by the Pleistocene Epoch. Prior to the 2009 revision of the geologic time scale, which placed the four most recent major glaciations entirely within the Pleistocene, the Pliocene also included the Gelasian stage, which lasted from 2.588 to 1.806 million years ago, and is now included in the Pleistocene.
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Acadian orogeny The Acadian orogeny is a long-lasting mountain building event which began in the Middle Devonian, reaching a climax in the early Late Devonian. It was active for approximately 50 million years, beginning roughly around 375 million years ago, with deformational, plutonic, and metamorphic events extending into the Early Mississippian. The Acadian orogeny is the third of the four orogenies that created the Appalachian orogen and subsequent basin. The preceding orogenies consisted of the Potomac and Taconic orogeny, which followed a rift/drift stage in the Late Neoproterozoic. The Acadian orogeny involved the collision of a series of Avalonian continental fragments with the Laurasian continent. Geographically, the Acadian orogen 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.
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Late Ordovician glaciation The Late Ordovician Glaciation is a period at the end of the Ordovician that started at the border between the Katian and Hirnantian about 440-460 Ma (million years ago). The major glaciation during this period is widely considered to be the leading cause of the Ordovician-Silurian extinction event. Evidence of this glaciation can be seen in places such as Morocco, South Africa, Libya, and Wyoming. More evidence derived from isotopic data is that during the Late Ordovician, Tropical ocean temperatures were about 5 °C cooler than present day, this would have been a major factor that aided in the glaciation process.
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Large igneous province In geology, a large igneous province (LIP) is an extremely large accumulation of igneous rocks, including plutonic rocks (intrusive) or volcanic rock formations (extrusive), arising when hot magma extrudes from inside the Earth and flows out. The source of many or all LIPs is variously attributed to mantle plumes or to processes associated with plate tectonics. Types of LIPs can include "large volcanic provinces" (LVP), created through flood basalt, and "large plutonic provinces" (LPP). Rampino and Stothers (1988) cite eleven distinct flood-basalt episodes - occurring in the past 250 million years - which created volcanic provinces and plateaus and coincided with mass extinctions. However, more flood basalts have been recognized, such as the large Ontong Java Plateau, and the medium-sized Chilcotin Group, though the latter may be linked to the Columbia River Basalt Group. Formation depends on a range of factors, such as continental configuration, latitude, volume, rate, duration of eruption, style and setting (continental vs. oceanic), the pre-existing climate state, and the biota resilience to change.
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Sonoma orogeny The Sonoma orogeny was a period of mountain building in western North America. The exact age and structure of the Sonoma orogeny is controversial. The orogeny is generally thought to have occurred during the Permian / Triassic transition, around 250 million years ago, following the Late Devonian Antler orogeny. The Sonoma orogeny was one of a sequence of accretionary events along the Cordilleran margin, possibly caused by the closure of the basin between the island arc of Sonomia and the North American continent. Evidence of this event has been reported throughout western North America, but most distinctly in northwest Nevada.
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Yokun Ridge Yokun Ridge is a ridge in the Taconic Mountains in Berkshire County, Massachusetts, consisting of a well-defined series of contiguous peaks including West Stockbridge Mountain and Lenox Mountain. The name "Yokun Ridge" was invented for the area in 1971 by a land conservation and environmental advocacy organization called the Berkshire Natural Resources Council, and was accepted in 2009 by the United States Board on Geographic Names. Yokun Ridge is 9 mi long and contains a conservation planning area called the Stockbridge-Yokun Ridge Reserve designated in 1993 by the U.S. Forest Service under its Forest Legacy Program. The ridge is notable for outdoor recreation and scenic beauty, as well as its conserved land and proximity to the tourist destinations of Lenox and Stockbridge. Yokun Ridge is located within West Stockbridge, Stockbridge, Lenox, Richmond, and Pittsfield, Massachusetts. Approximately one-third of the ridge is protected as open space reserve, municipal watershed, and wildlife sanctuary.
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South Teton South Teton (12514 ft ) is the fifth-highest peak in the Teton Range, Grand Teton National Park, in the U.S. state of Wyoming. The peak is south of Middle Teton and just west of Cloudveil Dome and is part of the Cathedral Group of high Teton peaks. The 40 mi Teton Range is the youngest mountain chain in the Rocky Mountains, and began their uplift 9 million years ago, during the Miocene. Several periods of glaciation have carved South Teton and the other peaks of the range into their current shapes.
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Hadean The Hadean ( ) is a geologic eon of the Earth predating the Archean. It began with the formation of the Earth about 4.6 billion years ago and ended, as defined by the ICS, 4 billion years ago. The geologist Preston Cloud coined the term in 1972, originally to label the period before the earliest-known rocks on Earth. W. Brian Harland later coined an almost synonymous term: the "Priscoan period". Other, older texts simply refer to the eon as the Pre-Archean.
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Paleocene–Eocene Thermal Maximum The Paleocene–Eocene Thermal Maximum (PETM), alternatively "Eocene thermal maximum 1" (ETM1), and formerly known as the "Initial Eocene" or "Late Paleocene Thermal Maximum " was a time period with more than 8 °C warmer global average temperature than today. This climate event began at the time boundary between the Paleocene and Eocene geological epochs. The exact age and duration of the event is uncertain but it is estimated to have occurred around 55.5 million years ago.
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Cool early Earth The cool early Earth ("CEE") theory posits that for part of the Hadean geological eon, at the beginning of the Earth's history, it had a modest influx of bolides and a cool climate, allowing the presence of liquid water. This would have been after the extreme conditions of earth's earliest history between 4.6 and 4.4 billion years (Ga) ago, but before the Late Heavy Bombardment of 4.1 to 3.8 Ga ago. In 2002 John Valley et al argued that detrital zircons found in Western Australia, dating to 4.0–4.4 Ga ago, were formed at relatively low temperatures, that meteorite impacts may have been less frequent than previously thought, and that the earth may have gone through long periods when liquid oceans and life were possible.