Basement (geology)

In geology, basement and crystalline basement are the rocks below a sedimentary platform or cover, or more generally any rock below sedimentary rocks or sedimentary basins that are metamorphic or igneous in origin. In the same way, the sediments or sedimentary rocks on top of the basement can be called a "cover" or "sedimentary cover".
Continental crust.
Basement rock is the thick foundation of ancient, and oldest, metamorphic and igneous rock that forms the crust of continents, often in the form of granite. Basement rock is contrasted to overlying sedimentary rocks which are laid down on top of the basement rocks after the continent was formed, such as sandstone and limestone. The sedimentary rocks which may be deposited on top of the basement usually form a relatively thin veneer, but can be more than 3 miles thick. The basement rock of the crust can be 20–30 miles thick, or more. The basement rock can be located under layers of sedimentary rock, or be visible at the surface.
Basement rock is visible, for example, at the bottom of the Grand Canyon, consisting of 1.7–2 billion year old granite (Zoroaster Granite) and schist (Vishnu Schist). The Vishnu Schist is believed to be highly metamorphosed igneous rocks and shale, from basalt, mud and clay laid from volcanic eruptions, and the granite is the result of magma intrusions into the Vishnu Schist. An extensive cross section of sedimentary rocks laid down on top of it through the ages is visible as well.
Age.
The basement rocks of the continental crust tend to be much older than the oceanic crust. The oceanic crust can be from 0–250 million years in age, and is usually thinner (10 miles or so) and composed of basaltic rocks. Continental crust is older because continental crust is light and thick enough so it is not subducted, while oceanic crust is periodically subducted and replaced at subduction and oceanic rifting areas.
Complexity.
The basement rocks are often highly metamorphosed and complex. They may consist of many different types of rock – volcanic, intrusive igneous and metamorphic. They may also contain fragments of oceanic crust that became wedged between plates when a terrane was accreted to the edge of the continent. Any of this material may be folded, refolded and metamorphosed. New igneous rock may freshly intrude into the crust from underneath, or may form underplating, where the new igneous rock forms a layer on the underside of the crust. It is said that the majority of continental crust on the planet is around 1–3 billion years old, and it is theorised that there was at least one period of rapid expansion and accretion to the continents during the Precambrian.
Much of the basement rock may have originally been oceanic crust, but it was highly metamorphosed and converted into continental crust via a series of events. A typical pattern is as follows. It is possible for oceanic crust to be subducted down into the Earth's mantle, at subduction fronts, where oceanic crust is being pushed down into the mantle by an overriding plate of oceanic or continental crust.
Volcanism.
When a plate of oceanic crust is subducted beneath an overriding plate of oceanic crust, as the underthrusting crust melts, it can cause upwelling of magma that can cause volcanism along the subduction front on the overriding plate. This produces an oceanic chain of volcanoes, like Japan. This volcanism causes metamorphism of rocks, intrusions of magma that produce rocks such as granite, and thickens the crust by depositing additional layers of rock from volcanoes. This tends to make the crust lighter and thicker, as a result making it immune to subduction.
Oceanic crust can be subducted, while continental crust cannot. Eventually, the subduction of the underthrusting oceanic crust can bring the volcano chain close to a continent, and collide with it. When the overriding plate collides with the continent, instead of being subducted, it is accreted to the edge of the continent and becomes a part of that continent. Thin strips or fragments of the underthrusting plate may also remain attached to the edge of the continent causing those fragments of oceanic crust to be wedged and tilted between the converging plates. In this manner, continents can grow over time as new terranes are accreted to their edges, and so continents can be composed of a complex quilt of terranes of varying ages.
As such, the basement rock can become younger going closer to the edge of the continent. There are exceptions, however, such as exotic terranes. Exotic terranes are pieces or fragments of other continents that have broken off their original parent continent and have become accreted to a different continent.
Cratons.
Many continents can consist of several continental cratons – blocks of crust built around an initial original core of continents – that gradually grew and expanded as additional newly created terranes were added to their edges. For instance, Pangea consisted of most of the Earth's continents being accreted into one giant supercontinent. Most continents, such as Asia, Africa and Europe, include several continental cratons, as they were formed by the accretion of many smaller continents.
Usage.
In European geology, the basement generally refers to rocks older than the Variscan orogeny. On top of this older basement Permian evaporites and Mesozoic limestones were deposited. The evaporites formed a weak zone on which the harder (stronger) limestone "cover" was able to move over the hard basement, making the distinction between basement and cover even more pronounced.
In Andean geology the basement refers to the Proterozoic, Paleozoic and early Mesozoic (Triassic to Jurassic) rock units as the basement to the late Mesozoic and Cenozoic Andean sequences developed following the onset of subduction along the western margin of the South American Plate.
When discussing the Trans-Mexican Volcanic Belt of Mexico the "basement" include Proterozoic, Paleozoic and Mesozoic age rocks for the Oaxaquia, the Mixteco and the Guerrero terranes respectively.
The term basement is used mostly in disciplines of geology like basin geology, sedimentology and petroleum geology in which the (typically Precambrian) crystalline basement is not of interest as it rarely contains petroleum or natural gas. The term "economic basement" is also used to describe the deeper parts of a cover sequence that are of no economic interest.


Perthite

Perthite is used to describe an intergrowth of two feldspars: a host grain of potassium-rich alkali feldspar (near K-feldspar, KAlSi3O8, in composition) includes exsolved lamellae or irregular intergrowths of sodic alkali feldspar (near albite, NaAlSi3O8, in composition). Typically the host grain is orthoclase or microcline, and the lamellae are albite. If sodic feldspar is the dominant phase, the result is an antiperthite and where the feldspars are in roughly equal proportions the result is a mesoperthite.
The intergrowth forms by exsolution due to cooling of a grain of alkali feldspar with a composition intermediate between K-feldspar and albite. There is complete solid solution between albite and K-feldspar at temperatures near 700 °C and pressures like those within the crust of the Earth, but a miscibility gap is present at lower temperatures. If an alkali feldspar grain with an intermediate composition cools slowly enough, K-rich and more Na-rich feldspar domains separate from one another. In the presence of water, the process occurs quickly.
When megascopically developed, the texture may consist of distinct pink and white lamellae representing exsolved white albite (NaAlSi3O8) in pink microcline. The intergrowths in perthite have a great variety of shapes. If cooling is sufficiently slow, the alkali feldspar may exsolve to form separate grains with near-endmember albite and K-feldspar compositions. The largest documented single crystal of perthite was found in Hugo Mine in South Dakota and measured about x x .
The gem varieties of potassium feldspar, amazonite and moonstone are variant colored perthites.


Herringbone cross-stratification

Herringbone cross-stratification is a type of sedimentary structure formed in tidal areas, such as tidal flats, where the current periodically flows in the opposite direction.
Formation.
During the conventional formation process of cross-stratification, sand grains saltate up the upstream side of the dune, collecting at the peak until the angle of repose is reached. At this point, the crest of granular material has grown too large and will be overcome by the force of the depositing fluid, falling down the downstream side of the dune. Repeated avalanches will eventually form the sedimentary structure known as cross-stratification, with the structure dipping in the direction of the paleocurrent.
In tidal areas, which have bidirectional flow, structures are formed with alternating layers of cross-beds dipping in opposite directions that reflect the alternating paleocurrent. These sedimentary structures are not common because they require the current to be equal in both directions, which rarely happens in nature. The time period represented by each cross-stratified layer is likely to be many years.
The pattern of the structure is said to resemble the backbone structure of a herring fish.


Wetheredella

Wetheredella is a genus of calcimicrobes known from the Silurian of England. It is suggested to be either a foraminifera, cyanobacterium or green alga. The genus is named in honor of the geologist Edward Wethered.
"Wetheredella" is characterized by calcified tubes encrusting a foreign body, with convex outer surfaces and inner surfaces coiled around the encrusted grain. Recently it has been shown that structures matching the description of "Wetheredella" can be produced by sectioning of "Allomena", meaning that "Wetheredella" is possibly a junior synonym of "Allomena".


Kerpen Formation

The Kerpen Formation is a geologic formation in Germany. It preserves fossils dating back to the Devonian period.


Sobkou Planitia

Sobkou Planitia is a large basin on the planet Mercury. It is named after the ancient Egyptian messenger deity Sobkou (whose name is more usually transliterated Sobek). He was associated by the Egyptians with the planet Mercury.
History.
Sobkou Planitia was discovered after Sobkou, the basin, was recognized as a Pre-Tolstojan basin on images from "Mariner 10".
Geology.
The most prominent features within the plain itself are a pair of craters, similar in size to one another, known as Brontë (Mercurian crater) and Degas (crater). Brontë is the older of the two craters, and the impact that formed Degas has overlapped the edges of that older crater and spread a spray of rays across the southern regions of Sobkou Planitia and beyond.
According to Peter Grego's book "Venus and Mercury and how to observe them" Sobkou Planitia is free of scarps, ridges, fractures and valleys. Its southeastern edge is bordered by the scarp Heemskerck Rupes (26N, 125W) which is about 300 km long which along part of the line of a very broad, bright swathe which is 1,000 km long and terminating just to the east of Chong Ch'ol (45N, 116W).


Orr Formation

The Orr Formation is a geologic formation in Utah. It preserves fossils dating back to the Cambrian period.


Portsdown Anticline

The Portsdown Anticline is a north-facing geological fold of Tertiary age affecting rocks in Hampshire, southern England. This upfold of the local sedimentary rock sequence is paralleled by the Bere Forest/Chichester Syncline (downfold) about 2km to its north and a postulated deep fault to the north again. Further west, this major east-west structure adopts more of a NW - SE alignment. At the surface the Portsdown Anticline is seen to affect the Chalk rocks of Late Cretaceous age at Ports Down though it is known to also affect the underlying Jurassic strata.


Paul S. Martin

Paul S. Martin (born in Allentown, Pennsylvania, 1928 - died in Tucson, Arizona September 13, 2010) was an American geoscientist at the University of Arizona who developed the theory that the Pleistocene extinction of large mammals worldwide was caused by overhunting by humans. Martin's work bridged the fields of ecology, anthropology, geosciences, and paleontology.
In 1953, Martin received his bachelor's degree in zoology from Cornell University. In 1953 and 1956 he completed his master's and doctorate programs at the University of Michigan and then proceeded with postdoctoral research at the Yale University and the University of Montreal. Martin's early interest embraced ornithology and herpetology and he conducted extensive fieldwork from 1948 to 1953 in Tamaulipas, Mexico. He published biogeographys on the birds of the Sierra de Tamaulipas and the herpetofauna of the Gómez Farias (= El Cielo) region of Tamaulipas, the latter considered "a classic treatise in historical biogeography". A case of polio, contracted while doing undergraduate field work in Mexico, forced Martin to rely on a cane, which restricted but did not end his field work. He joined the faculty of the University of Arizona in 1957 and worked there until his retirement in 1989.
Overkill hypothesis.
Martin developed the theory known as “overkill” or the “blitzkrieg model”, which, based on the ideas of Russian climatologist Mikhail I. Budyko, relates the sudden demise of large mammal populations on different continents and at different times to the arrival of humans. He believed that as they migrated from Africa and Eurasia to Australia, the Americas, and the islands of the Pacific, humans rapidly hunted the large animals endemic to each continent to extinction. Martin particularly focused his research on North America, whose late Ice Age fauna rivaled that of Africa today.
There, he theorized, around 11,000 years ago, newly arriving humans hunted North America's Ice Age large mammals, including ground sloths, camels, mammoths and mastodons, to extinction. The theory, summarized in "Twilight of the Mammoths: Ice Age Extinctions and the Rewilding of America" (2005) has been widely discussed and remained controversial. Critic Michael Fosha wrote that although Martin attempted to discuss and debunk alternative explanations of the extinction, he did not adequately examine mainstream theories like changes in climate and vegetation. According to Fosha, Martin presented a vivid account of prehistoric people's assault on nature "with the efficiency of a German panzer division" but Fosha felt that his views on archaeology were inaccurate. However, Fosha wrote that the book presents "excellent data on the Southwest" and deserves serious attention for it.
Martin sometimes faced criticism from archaeologists and paleontologists who claimed earlier dates for human arrival in the Americas or later dates for certain extinct animals than the overkill theory would suggest. Martin maintained that such claims were the result of faulty scientific analysis and pointed out that no such dates had yet been independently verified.
Martin's over-hunting hypothesis is still controversial. Several pre-Clovis sites are accepted by most workers, such as Topper, Monte Verde, Paisley Caves and others; dating of these is still controversial. New research has shown that in Siberia mammoths lived together with human beings for around 30,000 years, yet they became extinct only when the last glacial age ended. In Madagascar, there are more studies that predates the human arrival in the isle of several millennia.
Rewilding.
Martin also championed the concept of Pleistocene rewilding in which extinct North American Pleistocene fauna could be restored by establishing breeding populations of surviving animals from other continents such as llamas, camels, lions and cheetahs and introducing populations of animals analogous to extinct species, i.e., elephants for mammoths.
According to Vance Haynes, "unlike so many people who get infatuated with their own theories, he [Martin] spent his professional career inviting criticism. He put together two critical conferences about Pleistocene extinctions, and the volumes that came out of those were pace-setting."


Magma supply rate

The magma supply rate measures the production rate of magma at a volcano. Global magma production rates on Earth are about .
Definitions.
Magma supply rate is also known as the Armstrong unit, where 1 Armstrong Unit = . Armstrong unit can also refer to volcanic flux rate per length of arc in discussions of volcanic arcs, in that case km2/year.
Sometimes in discussion of large volcanic systems such as volcanic arcs the volcanic flux rate is normalized to a surface area, similar to Darcy's law in hydrodynamics. It is often easier to measure magma supply rates when they are normalized for an exposed surface area as it is often difficult to delimit an intrusion.
Measurement difficulties.
Estimating the volcanic flux rate or magma supply of a volcanic system is inherently difficult for a number of reasons, and different measurements can come to different conclusions about the volcanic flux rate of a given volcanic system. Not all volcanic bodies are equally well exposed, and it is often impossible or difficult to measure magma supply rates exactly. Furthermore, volcanic flux rates often vary over time, with distinct lulls and pulses. Wall rocks may be assimilated by magma or magma may undergo differentiation such as crystallization. Magma contains vesicles and volcanic edifices are often eroded. The sizes of volcanic edifices and plutons are difficult to estimate, especially in intrusions which are mostly buried.
Applications.
The magma supply rate is used to infer the behaviour of volcanic systems which erupt periodically, as well as to describe the growth of the continental crust and of deep-seated magmatic bodies such as plutons. Magma output is usually larger in oceanic settings than in continental ones, and basaltic volcanic systems produce more magma than silicic ones.


Crooked Creek Formation

The Crooked Creek Formation is a geologic formation in Kansas. It preserves fossils.


Chasm Creek Formation

The Chasm Creek Formation is a geologic formation in Manitoba. It preserves fossils dating back to the Ordovician period.


Tectonics

Tectonics (; ) are the processes that control the structure and properties of the Earth's crust and its evolution through time. These include the processes of mountain building, the growth and behavior of the strong, old cores of continents known as cratons, and the ways in which the relatively rigid plates that constitute the Earth's outer shell interact with each other. Tectonics also provide a framework for understanding the earthquake and volcanic belts that directly affect much of the global population.
Tectonic studies are important as guides for economic geologists searching for fossil fuels and ore deposits of metallic and nonmetallic resources. An understanding of tectonic principles is essential to geomorphologists to explain erosion patterns and other Earth surface features.
Main types of tectonic regime.
Extensional tectonics.
Extensional tectonics is associated with the stretching and thinning of the crust or the lithosphere. This type of tectonics is found at divergent plate boundaries, in continental rifts, during and after a period of continental collision caused by the lateral spreading of the thickened crust formed, at releasing bends in strike-slip faults, in back-arc basins, and on the continental end of passive margin sequences where a detachment layer is present.
Thrust (contractional) tectonics.
Thrust tectonics is associated with the shortening and thickening of the crust, or the lithosphere. This type of tectonics is found at zones of continental collision, at restraining bends in strike-slip faults, and at the oceanward part of passive margin sequences where a detachment layer is present.
Strike-slip tectonics.
Strike-slip tectonics is associated with the relative lateral movement of parts of the crust or the lithosphere. This type of tectonics is found along oceanic and continental transform faults which connect offset segments of mid-ocean ridges. Strike-slip tectonics also occurs at lateral offsets in extensional and thrust fault systems. In areas involved with plate collisions strike-slip deformation occurs in the over-riding plate in zones of oblique collision and accommodates deformation in the foreland to a collisional belt.
Plate tectonics.
In plate tectonics the outermost part of the Earththe crust and uppermost mantleare viewed as acting as a single mechanical layer, the lithosphere. The lithosphere is divided into separate "plates" that move relative to each other on the underlying, relatively weak asthenosphere in a process ultimately driven by the continuous loss of heat from the Earth's interior. There are three main types of plate boundaries: divergent, where plates move apart from each other and new lithosphere is formed in the process of sea-floor spreading; transform, where plates slide past each other, and convergent, where plates converge and lithosphere is "consumed" by the process of subduction. Convergent and transform boundaries form the largest structural discontinuities in the lithosphere and are responsible for most of the world's major (Mw > 7) earthquakes. Convergent and divergent boundaries are also the site of most of the world's volcanoes, such as around the Pacific Ring of Fire. Most of the deformation in the lithosphere is related to the interaction between plates, either directly or indirectly.
Other fields of tectonic studies.
Salt tectonics.
Salt tectonics is concerned with the structural geometries and deformation processes associated with the presence of significant thicknesses of rock salt within a sequence of rocks. This is due both to the low density of salt, which does not increase with burial, and its low strength.
Neotectonics.
Neotectonics is the study of the motions and deformations of the Earth's crust (geological and geomorphological processes) that are current or recent in geological time. The term may also refer to the motions and deformations themselves. The corresponding time frame is referred to as the "neotectonic period". Accordingly, the preceding time is referred to as "palaeotectonic period".
Tectonophysics.
Tectonophysics is the study of the physical processes associated with deformation of the crust and mantle from the scale of individual mineral grains up to that of tectonic plates.
Seismotectonics.
Seismotectonics is the study of the relationship between earthquakes, active tectonics, and individual faults in a region. It seeks to understand which faults are responsible for seismic activity in an area by analysing a combination of regional tectonics, recent instrumentally recorded events, accounts of historical earthquakes, and geomorphological evidence. This information can then be used to quantify the seismic hazard of an area.
Planetary tectonics.
Techniques used in the analysis of tectonics on Earth have also been applied to the study of the planets and their moons.


Dounans Limestone

The Dounans Limestone is a geologic formation in Scotland. It preserves fossils dating back to the Ordovician period.


Anahuac Formation

The Anahuac Formation is a geologic formation in Texas. It preserves fossils dating back to the Paleogene period.


Rib Hill Formation

The Rib Hill Formation is a geologic formation in Nevada. It preserves fossils dating back to the Permian period.


Disaster Peak Formation

The Disaster Peak Formation is a geologic formation in California. It preserves fossils dating back to the Neogene period.


Chancellor Group

The Chancellor Group is a geologic group in British Columbia. It preserves fossils dating back to the Cambrian period.


Klippe

A klippe (German for cliff or crag) is a geological feature of thrust fault terrains. The klippe is the remnant portion of a nappe after erosion has removed connecting portions of the nappe. This process results in an outlier of exotic, often nearly horizontally translated strata overlying autochthonous strata. Examples of klippes include:
Klippes may also be found in the Pre-Alps of Switzerland and some of the isolated mountains in Assynt, Sutherland, in NW Scotland.


Coleman Junction Formation

The Coleman Junction Formation is a geologic formation in Texas. It preserves fossils dating back to the Permian period.


Kamloops Formation

The Kamloops Formation is a geologic formation in British Columbia. It preserves fossils dating back to the Paleogene period.


Mars monolith

The Mars monolith is a rectangular object (possibly a boulder) discovered on the surface of Mars. It is located near the bottom of a cliff, from which it likely fell. The Mars Reconnaissance Orbiter took pictures of it from orbit, roughly 180 miles (300 km) away.
Around the same time, the Phobos monolith made international news.


Ratna Pariksha

Ratna Pariksha is an ancient science on testing gemstones. It was used by Kosadhyaksha (Superintendent of Treasury) mentioned in Kautilya's "Arthashastra" in order to control business of pearl, diamonds and all important gems in the ancient times. It classifies gemstones into Maha-Ratna and Upa-ratna
History.
Ratna Praiksha is mentioned in Kautilya's "Arthashastra" (323-299 B.C.). Vatsayana of Kamasutra mentions about rupa-ratna-pariksha. The method was also studied by princes in Karnataka during the medieval period.
The author of this treatise is very commonly known to be Buddha Bhatt. There is also mention of another author in medieval period, Thakkar Pheru, who is again credited to have worked on this subject. There's a mention of Vaidyaraj Shri Radha Krisha Navetia who uses Ratna Pariksha for preparing a type of alcohol meant in the use of gem therapy.


Goose Egg Formation

The Goose Egg Formation is a geologic formation in Wyoming. It preserves fossils dating back to the Permian period.


Alveolinidae

Alveolinidae is a family of spheroidal to fusiform milioline foraminfera with multiple apertures and complex interiors in which chambers are subdivided into chamberlets and subfloors interconnected by passageways. As with all Miliolina, the test wall in alveolinids is porecelaneous and imperforate. In living individuals the pseudopodea emerge through the multiple apertures that line the apertural or leading face of the test.
Alveolinids first appeared near the beginning of the Late Cretaceous, about 100 million years ago, some 150 million years after the superficially similar fusulinds became extinct at the end of the Permian.
Irregular coiling is found in the first volutions in the microspheric forms of most genera, indicating a close relationship with the Miliolidae. "Alveolinella" is an exception as the proloculus in the microspheric form is perforate and the first volutions are peneroplid in character, suggesting it, "Alveolinella", may have a different origin than the other alveolinids.


Bullion Creek Formation

The Bullion Creek Formation is a geologic formation in western North Dakota. It preserves bones and tracks of an extinct crocodile and other fossils of Late Paleocene age.


Impact structure

An impact structure is a generally circular or craterlike geologic structure of deformed bedrock or sediment produced by impact on a planetary surface, whatever the stage of erosion of the structure. In contrast, an impact crater is the surface expression of an impact structure. In many cases, on Earth, the impact crater has been destroyed by erosion, leaving only the deformed rock or sediment of the impact structure behind. This is the fate of almost all old impact craters on Earth, unlike the ancient pristine craters preserved on the Moon and other geologically inactive rocky bodies with old surfaces in the Solar System. Impact structure is synonymous with the less commonly used term astrobleme meaning "star wound".
In an impact structure, the typical visible and topographic expressions of an impact crater are no longer obvious. Any meteorite fragments that may once have been present would be long since eroded away. Possible impact structures may be initially recognized by their anomalous geological character or geophysical expression. These may still be confirmed as impact structures by the presence of shocked minerals (particularly shocked quartz), shatter cones, geochemical evidence of extraterrestrial material or other methods.


Rima Sharp

Rima Sharp is a sinuous rille on the moon, centered on selenographic coordinates 46.02°N 50.36°W. The name of the feature was approved by the IAU in 1964. It is named after the nearby crater Sharp.


Yogi Rock

Yogi Rock is a rock on Mars that was discovered during the Mars Pathfinder mission in 1997, and named by Geoffrey A. Landis. The rocks found on the mission were named after famous icons and figures, and Yogi Rock was thought to resemble the head of a bear looking away from the spacecraft. As a result, it was named for the famed cartoon character Yogi Bear.
The rock was the first on Mars found to be made of basalt, which suggests previous volcanic activity in the region as basalt is an igneous rock. The smoothness of the surface also suggested the past existence of water in the region. Yogi was also the first large rock reached by the "Sojourner" rover and was analyzed by an alpha proton X-ray spectrometer to determine its composition.
Images of "Sojourner" approaching Yogi used in the opening credits of "" made that television program the first science fiction television or film production in history to use footage taken on another planet.


Calaveras Fault

The Calaveras Fault is a major branch of the San Andreas Fault System that is located in northern California in the San Francisco Bay Area. Activity on the different segments of the fault includes moderate and large earthquakes as well as aseismic creep. The last large event was the 1984 Morgan Hill event and the last moderate earthquake was the 2007 Alum Rock event.
It is believed to link with the Hayward fault, as well as the West Napa Fault, north of the Carquinez Strait. It passes through or near the cities of Alamo, Danville, San Ramon, Dublin, Pleasanton, Sunol, Milpitas, San Jose, Gilroy, and Hollister.
Location.
To the east of the Hayward-Rodgers Creek fault, the Calaveras fault extends , splaying from the San Andreas fault near Hollister and terminating at Danville at its northern end. It runs east of the San Andreas, diverging from it in the vicinity of Hollister, California, and is responsible for the formation of the Calaveras Valley there. Between the San Andreas Fault and the Calaveras Fault lies the Hayward Fault, which diverges from the Calaveras Fault east of San Jose, California. To the east lies the Clayton-Marsh Creek-Greenville Fault. These four fault structures are some of the major faults in California at the latitude of San Francisco. All are right lateral-moving strike-slip faults.
The Calaveras Fault was named for Calaveras Creek in Santa Clara County east of San Jose where it was first identified. ("Calaveras" is Spanish for "skulls".) "Calaveras" is also the name of a California county in the foothills of the Sierra Nevada mountains, some east of Santa Clara County, far from the Calaveras Fault. Some of the cities which the Calaveras Fault passes through or near are: Alamo, Danville, San Ramon, Dublin, Pleasanton, Sunol, Milpitas, San Jose, Gilroy, and Hollister.
Related faults.
The West Napa Fault in Napa County is believed to be a continuation of the Calaveras Fault north of the Carquinez Strait. Between the faults lies an area of minor faults aligned "en echelon" known as the Contra Costa Shear Zone.
The minor Concord Fault lies to the east of the Calaveras Fault, and small earthquakes occur in the gap between faults, mostly in the vicinity of Alamo, California, relieving stresses generated by the displacement between the two faults. Stresses are also produced by offset and converging slip-strike motions between the Calaveras and Clayton-Marsh Creek-Greenville Fault that continue to elevate Mount Diablo. The compressive pressure is manifest in a significant thrust fault nearby on the western slope of the mountain, the Mount Diablo Thrust Fault, the most active of its kind in the region and which is also capable of producing significant local earthquakes affecting the Alamo-Danville area.
Tectonic forces.
The Pacific Plate is a major section of the Earth's crust, gradually expanding by the eruption of magma along the East Pacific Rise to the southeast. It is also being subducted far to the northwest into the Aleutian Trench under the North American Plate well north of San Francisco. In California, the plate is sliding northwestward along a transform boundary, the San Andreas Fault, toward the subduction zone. At the same time, the North American Plate is moving southwestward, but relatively southeast along the fault. The westward component of the North American Plate's motion results in some compressive force along the San Andreas and its associated faults such as the Calaveras Fault, thus helping lift the Coast Ranges. The Calaveras Fault shares the same relative motions of the San Andreas.
Seismic activity.
A number of magnitude 6 earthquakes have been recorded on the fault throughout recorded history, the largest of which was a magnitude 6.5 that occurred in 1911 in the Morgan Hill area. The most recent of these was a magnitude 6.2 earthquake near Morgan Hill in 1984.
A magnitude 5.6 earthquake occurred on the Calaveras Fault on October 30, 2007 at 20:04 PDT (October 31, at 03:04 UTC), near Alum Rock. Prior to the 2014 South Napa earthquake, it was the most powerful quake to hit the Bay Area since the Loma Prieta earthquake of 1989, and the largest on the Calaveras Fault since 1984.
Hayward Fault connection.
Although it has been known for some time that the Calaveras and Hayward faults merge in the South Bay region, recent geological studies suggest that the Calaveras and Hayward faults may be even more closely connected horizontally deep beneath the surface, angling toward each other with depth until they become a single fault. If true, this would have significant implications for the potential maximum strength of earthquakes on the Hayward, since this strength is determined by the maximum length of the fault rupture and this rupture could extend beyond the juncture point to include some portion of the Calaveras.
Recent assessment.
Assessments in January 2008 suggest that the northern Calaveras fault (the portion between Sunol and Danville) may be more likely to fail in the next few decades than previously thought.


Jackson Bluff Formation

The Jackson Bluff Formation is a geologic formation in Florida. It preserves fossils dating back to the Neogene period.


Waimakariri River

The Waimakariri River is one of the largest rivers in Canterbury, on the eastern coast of New Zealand's South Island. It flows for in a generally southeastward direction from the Southern Alps across the Canterbury Plains to the Pacific Ocean.
The river rises on the eastern flanks of the Southern Alps, eight kilometres southwest of Arthur's Pass. For much of its upper reaches, the river is braided, with wide shingle beds. As the river approaches the Canterbury Plains, it passes through a belt of mountains, and is forced into a narrow canyon (the Waimakariri Gorge), before reverting to its braided form for its passage across the plains. It enters the Pacific north of Christchurch, near the town of Kaiapoi.
Instead of being unoccupied crown land as are most New Zealand river beds, the bed of the Waimakariri River is vested in the Canterbury Regional Council (Environment Canterbury).
Name.
The exact Māori etymology of the name "Waimakariri" is not known. The most common translation for the name is "river of cold rushing water", derived from the Māori words "wai", meaning "water", and "makariri", meaning "cold". Additionally, both "mākā" and "riri" translate individually as vigorous or enraged respectively, making the exact etymological origins of the name difficult to determine. The river was briefly renamed as the Courtenay River in 1849 by the chief surveyor of the Canterbury Association, Joseph Thomas, in honour of Lord Courtenay. However, this name quickly fell into disuse in favour of the traditional Māori name. The Waimakariri is colloquially referred to as the 'Waimak', a shortening of the Māori name.
Geography.
The source of the Waimakariri is located in the Southern Alps, at the head of a valley to the west of Arthur's Pass, where it is primarily fed by snow melt and glacial runoff. The river flows in a southerly direction, before turning east around the base of Mount Stewart. The river at this stage becomes braided, and is joined by the Bealey River as it flows across wide shingle beds.
As the river is joined by the Esk River, the Waimakariri river is forced into a narrow series of gorges and ceases being braided. This continues as the river flows through the foothills of the Southern Alps, and is used by the Midland Line railway as part of its traverse of the Southern Alps. The river exits the foothills at the Waimakariri Gorge, at which point it again expands to a braided system.
Once on the Canterbury Plains, the Waimakariri flows in a roughly east-south-easterly direction towards the Pacific Ocean. As with other braided river systems, the main channels frequently change within the primary riverbed, especially during periods of high flow rates. Geological evidence indicates that this mobility has extended to the river itself in the past, at times flowing through the current location of Christchurch into what is now the Avon Heathcote Estuary, and on a separate occasion flowing into Lake Ellesmere / Te Waihora, to the south of Banks Peninsula. To protect Christchurch and other settlements near the river, multiple flood protections have been constructed either side of the river since European settlement, dating as early as the Canterbury Rivers Act 1868.
The river currently reaches the Pacific Ocean just to the north of Christchurch, entering Pegasus Bay by way of Brooklands Lagoon. The Waimakariri marks one of only a few breaks in the roughly length of Pegasus Bay. Along with two other rivers which enter Pegasus Bay (Ashley River / Rakahuri and Waipara River), the Waimakariri is almost entirely responsible for the sediment which forms the bay and its coastal plain.
Bridges.
Due to the size of the river, only a limited number of bridges cross the Waimakariri. From upstream to downstream, the current bridges are:
Bealey Bridge.
The Bealey Bridge is located immediately upstream from where the Bealey River flows into the Waimakariri. It is part of State Highway 73. Bealey Bridge is single-lane, with a passing bay in the middle. It is in a remote location and does not cater for pedestrians.
KiwiRail bridge #42.
Some downstream from the Bealey Bridge, the Midland Line crosses the river. KiwiRail records this bridge as number 42 on its bridge asset list. It is located where Red Beech Stream flows into the Waimakariri.
Mount White Bridge.
The Mount White Bridge is, "as the crow flies", located downstream from the KiwiRail bridge. It is much older than the Bealey Bridge. The abutment on the left bank of the Waimakariri is located within the delta created by the Hawdon River.
Waimakariri Gorge Bridge.
The Waimakariri Gorge Bridge is, "as the crow flies", located downstream from the Mount White bridge. This bridge was completed in 1877 and originally served both road and rail traffic (of the Oxford Branch). The bridge is on the register of Heritage New Zealand as a Category II structure.
SH1 Waimakariri Bridges.
The SH1 Waimakariri Bridges are twin bridges connecting Christchurch with the region north of the Waimakariri River via State Highway 1. It is located downstream from the Waimakariri Gorge Bridge. As part of the Christchurch Northern Motorway, each bridge was widened from two to three lanes during 2020, plus a cycleway added.
Main North Road bridge.
Just downstream from the state highway bridges is the Main North Road bridge, often referred to as the Old Waimakariri Bridge. This two-lane traffic bridge does not cater for walking or cycling.
Kiwirail bridge #17.
Immediately downstream from the Main North Road bridge, the Main North Line crosses the river. Kiwirail records this bridge as number 17 on its bridge asset list.
Ecology.
As one of the largest rivers on the Canterbury plains, the Waimakariri is an important habitat for wildlife, including many endangered species of both plants and animals. The dry sections of riverbed is home to Black-Fronted Terns, where braids in the river provide a natural barrier to predators. The river and its tributaries are home to multiple native species, including Crayfish / Kōura, New Zealand longfin eel, Short-finned Eel, as well as many other species of lampreys and invertebrates. The river is also one of the few remaining habitats for the critically endangered Canterbury mudfish (kowaro), which previously inhabited wetlands across the Canterbury plains, while a portion of its riverbank is home to one of only two known remaining populations of "Olearia adenocarpa".
Introduced fish are also common along the entirety of the Waimakariri River, making the river a popular location for fishing. As with most of New Zealand, this primarily includes brown and rainbow trout, as well as Chinook Salmon ("Oncorhynchus tshawytscha"). The Salmon population dates to the early 1900s, when they were introduced from California, and results in large salmon runs near the river mouth in Summer.
Development.
In 1923 the river was mainly investigated for a hydroelectric dam to supply electricity to Christchurch. It received support from the community but the dam was never built since the Government offered inexpensive electricity from the Lake Coleridge scheme.
The Central Plains Water Trust is proposing to take of water from two points on the Waimakariri River as part of the Central Plains Water enhancement scheme.
Pollution.
In 2007 the Waimakariri was ranked as one of the ten most polluted of the larger rivers in New Zealand. Some of the pollution was caused by liquid wastes from industries such as a meat processing plant and wool scourers in the vicinity of the river. The wastes were discharged directly into it but as of 2012 it was piped to the municipal sewage treatment plant. There had been some non-compliance issues with the resource consents for water discharge.


Cataclasite

Cataclasite is a cohesive granular fault rock. Comminution, also known as cataclasis, is an important process in forming cataclasites. They fall into the category of cataclastic rocks which are formed through faulting or fracturing in the upper crust. Cataclasites are distinguished from fault gouge, which is incohesive, and fault breccia, which contains coarser fragments.
Types.
Cataclasites are composed of fragments of the pre-existing wall rock as well as a matrix consisting of crushed microfragments, which cohesively holds the rock together. There are different types of classification schemes for cataclasites in the fault rock literature. The original classification scheme by Sibson classifies them by their proportion of fine-grained matrix to angular fragments. The term fault breccia is used for describing a cataclasite with coarser grains. A fault breccia is a cataclastic rock with clasts that are larger than 2 mm making up at least 30% of the rock.
These are the varieties based on the classification scheme of cataclasites proposed by Sibson:
This classification scheme separates distinct features of cataclasites, but any fault rock that has been formed through brittle deformation mechanisms containing pieces of the fractured pre-existing rock type are normally referred to as cataclasites. Cataclasites are different from mylonites, another type of fault rock, that is classified by the presence of a schistosity formed through ductile deformation methods.
Although cataclasites often lack an oriented fabric, some cataclasites are foliated. According to Sibson's 1975 classification scheme, these would be classified as mylonites although, through experiments, it was proven that some cataclastic mechanisms can form cataclasites with an oriented foliation solely due to brittle deformation. In a modification to the original definitions, the foliated fault rock would be still considered a cataclasite because it was created by cataclastic mechanisms.
Formation.
Cataclasites form though the progressive fracturing of mineral grains and aggregates, a process known as comminution. Cataclasites are the result of comminution, along with frictional sliding and grain rotation during faulting. This crushing, frictional sliding and rotation of grains is referred to as cataclasis.
Comminution, along with frictional sliding and grain boundary rotation can allow a rock to macroscopically flow over a wide brittle zone in the crust. This macroscopic flow due to the combination of brittle deformation mechanisms can be referred to as Deformation mechanism#Cataclasitic flow.
Setting.
Many faults near the earth's surface are brittle and show evidence of low temperature deformation. At low temperatures, there is not enough energy for the crystal grains to deform plastically, thus each grain fractures as opposed to elongation or recrystallizing. In these systems, cataclasites would be more likely to form as opposed to mylonites, which would require crystal plastic deformation. Due to quartz being the main mineral in many rocks in the brittle regime of the crust, the brittle-ductile transition for quartz can be a good indication of where cataclasites would form before ductile deformation plays a role. This normally refers to the uppermost 10–12 km of the continental crust.


Bayshore Formation

The Bayshore Formation is a geologic formation in Florida. It preserves fossils dating back to the Neogene period.


Pedestal crater

In planetary geology, a pedestal crater is a crater with its ejecta sitting above the surrounding terrain and thereby forming a raised platform (like a pedestal). They form when an impact crater ejects material which forms an erosion-resistant layer, thus causing the immediate area to erode more slowly than the rest of the region. Some pedestals have been accurately measured to be hundreds of meters above the surrounding area. This means that hundreds of meters of material were eroded away. The result is that both the crater and its ejecta blanket stand above the surroundings. Pedestal craters were first observed during the Mariner missions.
Description.
With further study, researchers have divided related craters into three different classes. and have advanced ideas about how they were formed. Excess ejecta craters and perched craters are larger than pedestal craters. All three have similar shapes with the bowl of the crater and an area around the bowl sitting above the surrounding surface. Excess ejecta craters and perched craters show ejecta deposits, but pedestal craters usually do not. All are found in the same regions and all seem to lie the same distance above the surroundings—an average of close to 50 meters.
The main difference between excess ejecta craters and perched craters is that the bowls of perched craters are shallow and sometimes almost full of material. Pedestal craters are near the center of a plateau that has an outward-facing scarp (cliff).
It is now believed that all three of these types of craters result from impacts into an icy layer. Excess ejecta craters and perched craters, the larger ones, penetrated completely through the ice layer and also went into a rocky lower layer. A portion of the rocky layer was deposited around the rim of the crater forming a rough ejecta deposit. That ejecta protected the area beneath it from erosion. Subsequent erosion left the craters sitting above the surrounding surface. The smaller, "pedestal craters," developed a protective covering by a different process. Simulations show that a large impact into ice would generate a great burst of heat that would be sufficient to melt some of the ice. The resulting water could dissolve salts and minerals and produce a coating resistant to erosion.
This new understanding of how these different craters have formed has helped the scientists to understand how ice-rich material was deposited in the mid-latitudes of both hemispheres a number of times in the Amazonian period on Mars, for example., During that time the obliquity (tilt) of the spin axis of Mars underwent many large variations. These changes caused the climate to change. With its current tilt, Mars has a thick deposit of ice at its poles. At times, the poles face the sun causing the polar ice to move to the mid-latitudes; it is during these times that ice-rich layers were formed.


Russell J. Hemley

Russell Julian Hemley (26 October 1954, Berkeley, California) is an American geophysicist, solid-state physicist, and physical chemist.
Hemley grew up in California, Colorado and Utah. He studied chemistry and philosophy at Wesleyan University with bachelor's degree in 1977 and then physical chemistry at Harvard University with master's degree in 1980 and Ph.D. in 1983. As a postdoc he was at Harvard University and was from 1984 to 1987 a Carnegie fellow at the Geophysical Laboratory of the Carnegie Institution in Washington D.C. From 1987 to 2016 he was a staff member of the Geophysical Laboratory, where he was from 2007 to 2013 the director.
In the academic year 1991–1992 he was a visiting scientist at the Johns Hopkins University and in 1996 and again in 1999 at the École normale supérieure de Lyon.
Hemley's research deals with the properties of matter under high pressure with applications in geophysics, geochemistry and planetology, as well as applications in solid-state physics, chemistry, and pressure effects on biomolecules and biological systems; the applications in physics include hydrogen under pressure in the megabar range, generation of novel superconductors, magnetic structures, glasses and superhard materials under high pressure; the applications in chemistry include new compounds under high pressure. Helmley's research has been experimental ("e.g." high-pressure studies with spectroscopic methods and generating high pressures with laser-heated diamond anvil cell) and theoretical; he used theory to develop high-pressure experimental methods in conjunction with microscopic laser-optical and X-ray diffraction analysis in situ from synchrotron radiation sources. Hemley worked in the late 1980s with Ho-Kwang Mao, who became famous for his 1976 work with Peter M. Bell on extension of the laboratory pressure range up to pressures over 1 megabar. Hemley, Mao, and Bell investigated not only minerals under pressures corresponding to those in the Earth's interior but also gases and liquids under pressures believed to exist in the interiors of gas giants such as Jupiter and Saturn. In particular, they investigated the behavior of hydrogen at pressures in the megabar range.
Hemley has published over 490 articles as an author or co-author and has been awarded several patents.
Hemley received in 2005 the Balzan Prize jointly with Ho-Kwang Mao and in 2009 the Bridgman Award. He is a fellow of the American Academy of Arts and Sciences, the American Geophysical Union and the American Physical Society. In 2001 he was elected a member of the National Academy of Sciences. Since 2003 he has been a member of the JASON Defense Advisory Group.


Nepheline syenite

Nepheline syenite is a holocrystalline plutonic rock that consists largely of nepheline and alkali feldspar. The rocks are mostly pale colored, grey or pink, and in general appearance they are not unlike granites, but dark green varieties are also known. Phonolite is the fine-grained extrusive equivalent.
Petrology.
Nepheline syenites are silica-undersaturated and some are peralkaline (terms discussed in igneous rock). Nepheline is a feldspathoid, a solid-solution mineral, that does not coexist with quartz; rather, nepheline would react with quartz to produce alkali feldspar.
They are distinguished from ordinary basic syenites not only by the presence of nepheline but also by the occurrence of many other minerals rich in alkalis and in rare earths and other incompatible elements. Alkali feldspar dominates, commonly represented by orthoclase and the exsolved lamellar albite, form perthite. In some rocks the potash feldspar, in others the soda feldspar predominates. Fresh clear microcline is very characteristic of some types of nepheline syenite.
Sodalite, colorless and transparent in thin section, but frequently pale blue in the hand specimens, is the principal feldspathoid mineral in addition to nepheline. Reddish-brown to black triclinic aenigmatite occurs also in these rocks. Extremely iron-rich olivine is rare, but is present in some nepheline syenite. Other minerals common in minor amounts include sodium-rich pyroxene, biotite, titanite, iron oxides, apatite, fluorite, melanite garnet, and zircon. Cancrinite occurs in several nepheline-syenites. A great number of interesting and rare minerals have been recorded from nepheline syenites and the pegmatite veins which intersect them.
Macroscopic aspects.
Macroscopic aspects of nepheline syenite are similar to those of granite. The presence of nepheline and absence of quartz are the fundamental difference. Biotite is generally of low content and the main mafic minerals are clinopyroxene (±) and amphibole (±). The macroscopic colour is grey, being little darker than granite. There is high-grade metamorphic rock originated from nepheline syenite that is characterized by gneiss texture of very rare occurrence. It is called nepheline syenite gneiss or litchfieldite. An example is found at Canaã village, State of Rio de Janeiro, Brazil.
Texture.
The rock is holocrystalline, generally equigranular, equidirectional, and gross with grain size of 2 mm to 5 mm. In certain rare cases, the rock contains alkaline feldspar phenocrysts of 2 cm to 5 cm in length and 5 mm to 2 cm in thickness. The phenocrysts demonstrate orientation and eventually show cumulative texture.
Mineral composition.
The main minerals are alkali feldspar, nepheline, clinopyroxene (±), amphibole (±), and biotite (±). Nepheline is the main feldspathoid. Quartz and orthopyroxene are absent. According to the IUGS classification nomenclature (International Union of Geological Sciences, Streckeisen, 1978), nepheline syenite has 10% < "F"/("F" + "A" + "P") < 60% and "P"/("A" + "P") < 10% (where "F" – feldspathoids, "A" – alkali feldspar, and "P" – plagioclase volume fractions). Phonolite is the fine-grained equivalent. In case nepheline is less than 10%, the rock is called alkaline syenite with nepheline or pulaskite. The similar rock without quartz and nepheline is denominated alkaline syenite or syenite. Because of the presence of feldspathoids, nepheline syenite is classified to be a typical alkaline rock.
The alkaline feldspar is not potassic, but generally sodic-potassic, which is characterized by interlocking anorthoclase, called perthite. In the alkali feldspar almost pure albite domains are observed. Nepheline generally shows partial alteration into natrolite and cancrinite. The clinopyroxene is sodic whose composition varies from hedenbergite to aegirine-augite. This mineral eventually presents resorption shape. The reaction rim constituted by amphibole and/or biotite is commonly observed. The amphibole is of high alkali, such as alkaline hornblende and riebeckite. The alkaline clinopyroxene and amphibole are characteristics of typical alkaline rocks. Biotite is annite, with high Fe/Mg ratio.
The accessory minerals are magnetite, ilmenite, apatite, and titanite. Eventually, sodalite is found along hydrothermal fractures. Different from granite, zircon is rare and, if present, it is as xenocrysts. On the other hand, nepheline syenite gneiss contains abundant and large zircon crystals.
Genesis.
Silica-undersaturated igneous rocks typically are formed by low degrees of partial melting in the Earth's mantle. Carbon dioxide may dominate over water in source regions. Magmas of such rocks are formed in a variety of environments, including continental rifts, ocean islands, and supra-subduction positions in subduction zones. Nepheline syenite and phonolite may be derived by crystal fractionation from more mafic silica-undersaturated mantle-derived melts, or as partial melts of such rocks. Igneous rocks with nepheline in their normative mineralogy commonly are associated with other unusual igneous rocks such as carbonatite.
Distribution.
Nepheline syenites and phonolites occur, for example, in Brazil, Canada, Cameroon, China, Greenland, Italy, Norway, the Pyrenees, Sweden, the Transvaal region, the Ural Mountains, in the USA Magnet Cove igneous complex of Arkansas, the mountains of the Central Montana Alkali Province, and as well as on oceanic islands.
Phonolite lavas formed in the East African rift in particularly large quantity, and the volume there may exceed the volume of all other phonolite occurrences combined, as discussed by Barker (1983).
Nepheline-normative rocks occur in close association with the Bushveld Igneous Complex, possibly formed from partial melting of the wall rocks to that large ultramafic layered intrusion.
Nepheline syenites are rare; there is only one occurrence in Great Britain (Loch Borralan) and one in France and Portugal. They are known also in Bohemia and in several places in Norway, Sweden and Finland. In the Americas these rocks have been found in Texas, Arkansas, New Jersey (Beemerville Complex) and Massachusetts, also in Ontario, British Columbia and Brazil. South Africa, Madagascar, India, Tasmania, Timor and Turkestan are other localities for the rocks of this series.
Rocks of this class also occur in Brazil (Serra de Tingua) containing sodalite and often much augite, in the western Sahara and Cape Verde Islands; also at Zwarte Koppies in the Transvaal, Madagascar, São Paulo in Brazil, Paisano Pass in West Texas, United States, and Montreal, Quebec, Canada. The rock of Salem, Massachusetts, United States, is a mica-foyaite rich in albite and aegirine: it accompanies granite and essexite. Litchfieldite is another well-marked type of nepheline-syenite, in which albite is the dominant feldspar. It is named after Litchfield, Maine, United States, where it occurs in scattered blocks. Biotite, cancrinite and sodalite are characteristic of this rock. A similar nepheline-syenite is known from Hastings County, Ontario, and contains hardly any orthoclase, but only albite feldspar. Nepheline is very abundant and there is also cancrinite, sodalite, scapolite, calcite, biotite and hornblende. The lujaurites are distinguished from the rocks above described by their dark color, which is due to the abundance of minerals such as augite, aegirine, arfvedsonite and other kinds of amphibole. Typical examples are known near Lujaur on the White Sea, where they occur with umptekites and other very peculiar rocks. Other localities for this group are at Julianehaab in Greenland with sodalite-syenite; at their margins they contain pseudomorphs after leucite. The lujaurites frequently have a parallel-banding or gneissose structure. Sodalite-syenites in which sodalite very largely or completely takes the place of nepheline occur in Greenland, where they contain also microcline-perthite, aegirine, arfvedsonite and eudialyte.
Cancrinite syenite, with a large percentage of cancrinite, has been described from Dalekarlia, Sweden and from Finland. Urtite from Lujaur Urt on the White Sea consists very largely of nepheline, with aegirine and apatite, but no feldspar. Jacupirangite (from Jacupiranga in Brazil) is a blackish rock composed of titaniferous augite, magnetite, ilmenite, perofskite and nepheline, with secondary biotite.
Nomenclature.
There is a wide variety of silica-undersaturated and peralkaline igneous rocks, including many informal place-name varieties named after the locations in which they were first discovered. In many cases these are plain nepheline syenites containing one or more rare minerals or mineraloids, which do not warrant a new formal classification. These include;
"Foyaite": foyaites are named after Foya in the Serra de Monchique, in southern Portugal. These are K-feldspar-nepheline syenites containing <10% ferromagnesian minerals, usually pyroxene, hornblende and biotite.
"Laurdalite": The laurdalites, from Laurdal in Norway, are grey or pinkish, and in many ways closely resemble the larvikites of southern Norway, with which they occur. They contain anorthoclase feldspars, biotite or greenish augite, much apatite and in some cases, olivine.
"Ditroite": Ditroite derives its name from Ditrau, Transylvania, Romania. It is essentially a microcline, sodalite and cancrinite variety of nepheline syenite. It contains also orthoclase, nepheline, biotite, aegirine, acmite.
Chemical composition.
The chemical peculiarities of the nepheline-syenites are well marked. They are exceedingly rich in alkalis and in alumina (hence the abundance of felspathoids and alkali feldspars), with silica varying from 50 to 56%, while lime, magnesia and iron are never present in great quantity, though somewhat more variable than the other components. A worldwide average of the major elements in nepheline syenite tabulated by Barker (1983) is listed below, expressed as weight percent oxides.
Nepheline syenite is characterized by high ratio of (Na2O+K2O)/SiO2 and (Na2O+K2O)/Al2O3, which are represented respectively by the existence of nepheline and alkaline mafic minerals. Therefore, it is classified geochemically as alkaline rock. This rock has low Fe and Mg contents, in total about 3wt%, and in this sense it is classified to be felsic rock. However, the SiO2 content is not so high, being 53% to 62wt%, which is equivalent to andesite and diorite. In this sense, it corresponds to intermediate rock. Light rare-earth elements are highly concentrated, indicating that the magma is highly differentiated.
The normative mineralogy of this average composition contains about 22% nepheline and 66% feldspar.
Because nepheline syenite lacks quartz and is rich in feldspar and nepheline, it is used in the manufacturing of glass and ceramics.
Uses.
Nepheline syenite provides geological clues to environment of formation. It also provides a source of unusual mineral specimens and rare-earth elements (REE) extraction.
The industrial use of nepheline syenite includes refractories, glass making, ceramics and, in pigments and fillers. In these applications the nepheline syenite is ground and dark minerals are carefully separated leaving a mixture of primarily felspar and nepheline. This mixture is higher in alkali and aluminium and typically lower in iron than felspars from pegmatites making it a good raw material.


Black Forest Observatory

Black Forest Observatory (BFO) or Observatorium Schiltach is a geophysical observatory owned and operated by Karlsruhe University and Stuttgart University. It is located near Schiltach in the Black Forest region of Baden-Württemberg, in southwest Germany. The observatory is in the Anton mine, which was abandoned and then converted in 1972.


Naco Group

The Naco Group is a geologic group in Arizona. It preserves fossils dating back to the Permian period.


List of pterosaur type specimens

This list of pterosaur type specimens is a list of fossils serving as the official standard-bearers for inclusion in the species and genera of the reptile clade Pterosauria, which includes the famous winged reptiles of the Mesozoic. Type specimens are definitionally members of biological taxa, and additional specimens can only be "referred" to these taxa if an expert deems them sufficiently similar to the type.


Ituxi Vallis

Ituxi Vallis is a valley in the Elysium quadrangle of Mars, located at 25.4° N and 207° W. It is 62 km long and was named after the Ituxi River in Brazil.


Metamorphic rock

Metamorphic rocks arise from the transformation of existing rock to new types of rock, in a process called metamorphism. The original rock (protolith) is subjected to temperatures greater than and, often, elevated pressure ( or more), causing profound physical or chemical changes. During this process, the rock remains mostly in the solid state, but gradually recrystallizes to a new texture or mineral composition. The protolith may be a sedimentary, igneous, or existing metamorphic rock.
Metamorphic rocks make up a large part of the Earth's crust and form 12% of the Earth's land surface. They are classified by their protolith, their chemical and mineral makeup, and their texture. They may be formed simply by being deeply buried beneath the Earth's surface, where they are subject to high temperatures and the great pressure of the rock layers above. They can also form from tectonic processes such as continental collisions, which cause horizontal pressure, friction and distortion. Metamorphic rock can be formed locally when rock is heated by the intrusion of hot molten rock called magma from the Earth's interior. The study of metamorphic rocks (now exposed at the Earth's surface following erosion and uplift) provides information about the temperatures and pressures that occur at great depths within the Earth's crust.
Some examples of metamorphic rocks are gneiss, slate, marble, schist, and quartzite. Slate and quartzite tiles are used in building construction. Marble is also prized for building construction and as a medium for sculpture. On the other hand, schist bedrock can pose a challenge for civil engineering because of its pronounced planes of weakness.
Origin.
Metamorphic rocks form one of the three great divisions of rock types. They are distinguished from igneous rocks, which form from molten magma, and sedimentary rocks, which form from sediments eroded from existing rock or precipitated chemically from bodies of water.
Metamorphic rocks are formed when existing rock is transformed physically or chemically at elevated temperature, without actually melting to any great degree. The importance of heating in the formation of metamorphic rock was first noted by the pioneering Scottish naturalist, James Hutton, who is often described as the father of modern geology. Hutton wrote in 1795 that some rock beds of the Scottish Highlands had originally been sedimentary rock, but had been transformed by great heat.
Hutton also speculated that pressure was important in metamorphism. This hypothesis was tested by his friend, James Hall, who sealed chalk into a makeshift pressure vessel constructed from a cannon barrel and heated it in an iron foundry furnace. Hall found that this produced a material strongly resembling marble, rather than the usual quicklime produced by heating of chalk in the open air. French geologists subsequently added metasomatism, the circulation of fluids through buried rock, to the list of processes that help bring about metamorphism. However, metamorphism can take place without metasomatism ("isochemical metamorphism") or at depths of just a few hundred meters where pressures are relatively low (for example, in "contact metamorphism").
Metamorphic processes change the texture or mineral composition of the metamorphosed rock.
Mineralogical changes.
Metasomatism can change the bulk composition of a rock. Hot fluids circulating through pore space in the rock can dissolve existing minerals and precipitate new minerals. Dissolved substances are transported out of the rock by the fluids while new substances are brought in by fresh fluids. This can obviously change the mineral makeup of the rock.
However, changes in the mineral composition can take place even when the bulk composition of the rock does not change. This is possible because all minerals are stable only within certain limits of temperature, pressure, and chemical environment. For example, at atmospheric pressure, the mineral kyanite transforms to andalusite at a temperature of about . Andalusite, in turn, transforms to sillimanite when the temperature reaches about . All three have the identical composition, . Likewise, forsterite is stable over a broad range of pressure and temperature in marble, but is converted to pyroxene at elevated pressure and temperature in more silicate-rich rock containing plagioclase, with which the forsterite reacts chemically.
Many complex high-temperature reactions may take place between minerals without them melting, and each mineral assemblage produced provides us with a clue as to the temperatures and pressures at the time of metamorphism. These reactions are possible because of rapid diffusion of atoms at elevated temperature. Pore fluid between mineral grains can be an important medium through which atoms are exchanged.
Textural changes.
The change in the particle size of the rock during the process of metamorphism is called recrystallization. For instance, the small calcite crystals in the sedimentary rock limestone and chalk change into larger crystals in the metamorphic rock marble. In metamorphosed sandstone, recrystallization of the original quartz sand grains results in very compact quartzite, also known as metaquartzite, in which the often larger quartz crystals are interlocked. Both high temperatures and pressures contribute to recrystallization. High temperatures allow the atoms and ions in solid crystals to migrate, thus reorganizing the crystals, while high pressures cause solution of the crystals within the rock at their point of contact.
Description.
Metamorphic rocks are characterized by their distinctive mineral composition and texture.
Metamorphic minerals.
Because every mineral is stable only within certain limits, the presence of certain minerals in metamorphic rocks indicates the approximate temperatures and pressures at which the rock underwent metamorphosis. These minerals are known as index minerals. Examples include sillimanite, kyanite, staurolite, andalusite, and some garnet.
Other minerals, such as olivines, pyroxenes, hornblende, micas, feldspars, and quartz, may be found in metamorphic rocks, but are not necessarily the result of the process of metamorphism. These minerals can also form during the crystallization of igneous rocks. They are stable at high temperatures and pressures and may remain chemically unchanged during the metamorphic process.
Texture.
Metamorphic rocks are typically more coarsely crystalline than the protolith from which they formed. Atoms in the interior of a crystal are surrounded by a stable arrangement of neighboring atoms. This is partially missing at the surface of the crystal, producing a "surface energy" that makes the surface thermodynamically unstable. Recrystallization to coarser crystals reduces the surface area and so minimizes the surface energy.
Although grain coarsening is a common result of metamorphism, rock that is intensely deformed may eliminate strain energy by recrystallizing as a fine-grained rock called "mylonite". Certain kinds of rock, such as those rich in quartz, carbonate minerals, or olivine, are particularly prone to form mylonites, while feldspar and garnet are resistant to mylonitization.
Foliation.
Many kinds of metamorphic rocks show a distinctive layering called "foliation" (derived from the Latin word "folia", meaning "leaves"). Foliation develops when a rock is being shortened along one axis during recrystallization. This causes crystals of platy minerals, such as mica and chlorite, to become rotated such that their short axes are parallel to the direction of shortening. This results in a banded, or foliated, rock, with the bands showing the colors of the minerals that formed them. Foliated rock often develops planes of cleavage. Slate is an example of a foliated metamorphic rock, originating from shale, and it typically shows well-developed cleavage that allows slate to be split into thin plates.
The type of foliation that develops depends on the metamorphic grade. For instance, starting with a mudstone, the following sequence develops with increasing temperature: The mudstone is first converted to slate, which is a very fine-grained, foliated metamorphic rock, characteristic of very low grade metamorphism. Slate in turn is converted to phyllite, which is fine-grained and found in areas of low grade metamorphism. Schist is medium to coarse-grained and found in areas of medium grade metamorphism. High-grade metamorphism transforms the rock to gneiss, which is coarse to very coarse-grained.
Rocks that were subjected to uniform pressure from all sides, or those that lack minerals with distinctive growth habits, will not be foliated. Marble lacks platy minerals and is generally not foliated, which allows its use as a material for sculpture and architecture.
Classification.
Metamorphic rocks are one of the three great divisions of all rock types, and so there is a great variety of metamorphic rock types. In general, if the protolith of a metamorphic rock can be determined, the rock is described by adding the prefix "meta-" to the protolith rock name. For example, if the protolith is known to be basalt, the rock will be described as a metabasalt. Likewise, a metamorphic rock whose protolith is known to be a conglomerate will be described as a metaconglomerate. For a metamorphic rock to be classified in this manner, the protolith should be identifiable from the characteristics of the metamorphic rock itself, and not inferred from other information.
Under the British Geological Society classification system, if all that can be determined about the protolith is its general type, such as sedimentary or volcanic, the classification is based on the mineral mode (the volume percentages of different minerals in the rock). Metasedimentary rocks are divided into carbonate-rich rock (metacarbonates or calcsilicate-rocks) or carbonate-poor rocks, and the latter are further classified by the relative abundance of mica in their composition. This ranges from low-mica psammite through semipellite to high-mica pellite. Psammites composed mostly of quartz are classified as quartzite. Metaigneous rocks are classified similarly to igneous rocks, by silica content, from meta-ultramafic-rock (which is very low in silica) to metafelsic-rock (with a high silica content).
Where the mineral mode cannot be determined, as is often the case when rock is first examined in the field, then classification must be based on texture. The textural types are:
A hornfels is a granofels that is known to result from contact metamorphism. A slate is a fine-grained metamorphic rock that easily splits into thin plates but shows no obvious compositional layering. The term is used only when very little else is known about the rock that would allow a more definite classification. Textural classifications may be prefixed to indicate a sedimentary protolith ("para-", such as paraschist) or igneous protolith ("ortho-", such as orthogneiss). When nothing is known about the protolith, the textural name is used without a prefix. For example, a schist is a rock with schistose texture whose protolith is uncertain.
Special classifications exist for metamorphic rocks with a volcaniclastic protolith or formed along a fault or through hydrothermal circulation. A few special names are used for rocks of unknown protolith but known modal composition, such as marble, eclogite, or amphibolite. Special names may also be applied more generally to rocks dominated by a single mineral, or with a distinctive composition or mode or origin. Special names still in wide use include amphibolite, greenschist, phyllite, marble, serpentinite, eclogite, migmatite, skarn, granulite, mylonite, and slate.
The basic classification can be supplemented by terms describing mineral content or texture. For example, a metabasalt showing weak schistosity might be described as a gneissic metabasalt, and a pellite containing abundant staurolite might be described as a staurolite pellite.
Metamorphic facies.
A metamorphic facies is a set of distinctive assemblages of minerals that are found in metamorphic rock that formed under a specific combination of pressure and temperature. The particular assemblage is somewhat dependent on the composition of that protolith, so that (for example) the amphibolite facies of a marble will not be identical with the amphibolite facies of a pellite. However, the facies are defined such that metamorphic rock with as broad a range of compositions as is practical can be assigned to a particular facies. The present definition of metamorphic facies is largely based on the work of the Finnish geologist, Pentti Eskola, with refinements based on subsequent experimental work. Eskola drew upon the zonal schemes, based on index minerals, that were pioneered by the British geologist, George Barrow.
The metamorphic facies is not usually considered when classifying metamorphic rock based on protolith, mineral mode, or texture. However, a few metamorphic facies produce rock of such distinctive character that the facies name is used for the rock when more precise classification is not possible. The chief examples are amphibolite and eclogite. The British Geological Survey strongly discourages use of "granulite" as a classification for rock metamorphosed to the granulite facies. Instead, such rock will often be classified as a granofels. However, this is not universally accepted.
Occurrence.
Metamorphic rocks make up a large part of the Earth's crust and form 12% of the Earth's land surface. The lower continental crust is mostly metamafic-rock and pellite which have reached the granulite facies. The middle continental crust is dominated by metamorphic rock that has reached the amphibolite facies. Within the upper crust, which is the only part of the Earth's crust geologists can directly sample, metamorphic rock forms only from processes that can occur at shallow depth. These are "contact (thermal) metamorphism", "dynamic (cataclastic) metamorphism", "hydrothermal metamorphism", and "impact metamorphism". These processes are relatively local in occurrence and usually reach only the low-pressure facies, such as the hornfels and sanidinite facies. Most metamorphic rock is formed by "regional metamorphism" in the middle and lower crust, where the rock reaches the higher-pressure metamorphic facies. This rock is found at the surface only where extensive uplift and erosion has exhumed rock that was formerly much deeper in the crust.
Orogenic belts.
Metamorphic rock is extensively exposed in orogenic belts produced by the collision of tectonic plates at convergent boundaries. Here formerly deeply buried rock has been brought to the surface by uplift and erosion. The metamorphic rock exposed in orogenic belts may have been metamorphosed simply by being at great depths below the Earth's surface, subjected to high temperatures and the great pressure caused by the immense weight of the rock layers above. This kind of regional metamorphism is known as "burial metamorphism". This tends to produced low-grade metamorphic rock. Much more common is metamorphic rock formed during the collision process itself. The collision of plates causes high temperatures, pressures and deformation in the rocks along these belts. Metamorphic rock formed in these settings tends to shown well-developed schistosity.
Metamorphic rock of orogenic belts shows a variety of metamorphic facies. Where subduction is taking place, the basalt of the subducting slab is metamorphosed to high-pressure metamorphic facies. It initially undergoes low-grade metamorphism to metabasalt of the zeolite and prehnite-pumpellyite facies, but as the basalt subducts to greater depths, it is metamorphosed to the blueschist facies and then the eclogite facies. Metamorphism to the eclogite facies releases a great deal of water vapor from the rock, which drives volcanism in the overlying volcanic arc. Eclogite is also significantly denser than blueschist, which drives further subduction of the slab deep into the Earth's mantle. Metabasalt and blueschist may be preserved in blueschist metamorphic belts formed by collisions between continents. They may also be preserved by obduction onto the overriding plate as part of ophiolites. Eclogites are occasionally found at sites of continental collision, where the subducted rock is rapidly brought back to the surface, before it can be converted to the granulite facies in the hot upper mantle. Many samples of eclogite are xenoliths brought to the surface by volcanic activity.
Many orogenic belts contain higher-temperature, lower-pressure metamorphic belts. These may form through heating of the rock by ascending magmas of volcanic arcs, but on a regional scale. Deformation and crustal thickening in an orogenic belt may also produce these kinds of metamorphic rocks. These rocks reach the greenschist, amphibolite, or granulite facies and are the most common of metamorphic rocks produced by regional metamorphosis. The association of an outer high-pressure, low-temperature metamorphic zone with an inner zone of low-pressure, high-temperature metamorphic rocks is called a "paired metamorphic belt". The main islands of Japan show three distinct paired metamorphic belts, corresponding to different episodes of subduction.
Metamorphic core complexes.
Metamorphic rock is also exposed in metamorphic core complexes, which form in region of crustal extension. They are characterized by low-angle faulting that exposes domes of middle or lower crust metamorphic rock. These were first recognized and studied in the Basin and Range Province of southwestern North America, but are also found in southern Aegean Sea, in the D'Entrecasteaux Islands, and in other areas of extension.
Granite-greenstone belts.
Continental shields are regions of exposed ancient rock that make up the stable cores of continents. The rock exposed in the oldest regions of shields, which is of Archean age (over 2500 million years old), mostly belong to granite-greenstone belts. The greenstone belts contain metavolcanic and metasedimentary rock that has undergone a relatively mild grade of metamorphism, at temperatures of and pressures of . They can be divided into a lower group of metabasalts, including rare metakomatiites; a middle group of meta-intermediate-rock and meta-felsic-rock; and an upper group of metasedimentary rock.
The greenstone belts are surrounded by high-grade gneiss terrains showing highly deformed low-pressure, high-temperature (over ) metamorphism to the amphibolite or granulite facies. These form most of the exposed rock in Archean cratons.
The granite-greenstone belts are intruded by a distinctive group of granitic rocks called the tonalite-trondhjemite-granodiorite or TTG suite. These are the most voluminous rocks in the craton and may represent an important early phase in the formation of continental crust.
Mid-ocean ridges.
Mid-ocean ridges are where new oceanic crust is formed as tectonic plates move apart. Hydrothermal metamorphism is extensive here. This is characterized by metasomatism by hot fluids circulating through the rock. This produces metamorphic rock of the greenschist facies. The metamorphic rock, serpentinite, is particularly characteristic of these settings, and represents chemical transformation of olivine and pyroxene in ultramafic rock to serpentine group minerals.
Contact aureoles.
Contact metamorphism takes place when magma is injected into the surrounding solid rock (country rock). The changes that occur are greatest wherever the magma comes into contact with the rock because the temperatures are highest at this boundary and decrease with distance from it. Around the igneous rock that forms from the cooling magma is a metamorphosed zone called a "contact aureole". Aureoles may show all degrees of metamorphism from the contact area to unmetamorphosed (unchanged) country rock some distance away. The formation of important ore minerals may occur by the process of metasomatism at or near the contact zone. Contact aureoles around large plutons may be as much as several kilometers wide.
The term "hornfels" is often used by geologists to signify those fine grained, compact, non-foliated products of contact metamorphism. The contact aureole typically shows little deformation, and so hornfels is usually devoid of schistosity and forms a tough, equigranular rock. If the rock was originally banded or foliated (as, for example, a laminated sandstone or a foliated calc-schist) this character may not be obliterated, and a banded hornfels is the product. Contact metamorphism close to the surface produces distinctive low-pressure metamorphic minerals, such as spinel, andalusite, vesuvianite, or wollastonite.
Similar changes may be induced in shales by the burning of coal seams. This produces a rock type named "clinker".
There is also a tendency for metasomatism between the igneous magma and sedimentary country rock, whereby the chemicals in each are exchanged or introduced into the other. In that case, hybrid rocks called skarn arise.
Other occurrences.
Dyamic (cataclastic) metamorphism takes place locally along faults. Here intense shearing of the rock typically forms mylonites.
Impact metamorphism is unlike other forms of metamorphism in that it takes place during impact events by extraterrestrial bodies. It produces rare ultrahigh pressure metamorphic minerals, such as coesite and stishovite. Coesite is rarely found in eclogite brought to the surface in kimberlite pipes, but the presence of stishovite is unique to impact structures.
Uses.
Slate tiles are used in construction, particularly as roof shingle.
Quartzite is sufficiently hard and dense that it is difficult to quarry. However, some quartzite is used as dimension stone, often as slabs for flooring, walls, or stair steps. About 6% of crushed stone, used mostly for road aggregate, is quartzite.
Marble is also prized for building construction and as a medium for sculpture.
Hazards.
Schistose bedrock can pose a challenge for civil engineering because of its pronounced planes of weakness. A hazard may exist even in undisturbed terrain. On August 17, 1959, a magnitude 7.2 earthquake destabilized a mountain slope near Hebgen Lake, Montana, composed of schist. This caused a massive landslide that killed 26 people camping in the area.
Metamorphosed ultramafic rock contains serpentine group minerals, which includes varieties of asbestos that pose a hazard to human health.


Corpulentapus

Corpulentapus is an ichnogenus of Early Cretaceous theropod tracks uncovered at the Zhucheng tracksite in Shandong, PR China.


Marnes de Dormans

The Marnes de Dormans is a geologic formation in France. It preserves fossils dating back to the Paleogene period.


Purbeckopus

Purbeckopus is an ichnotaxon of pterosaur of the family Pteraichnidae. Considered as a "nomen dubium", it lived in southern England during the Berriasian, in the Upper Cretaceous. According to the fossil remains found, it is expected that it was a large pterosaur, with 6 m (19.7 ft) in wingspan.


The Storr

The Storr () is a rocky hill on the Trotternish peninsula of the Isle of Skye in Scotland. The hill presents a steep rocky eastern face overlooking the Sound of Raasay, contrasting with gentler grassy slopes to the west.
Geology.
The Storr is a prime example of the Trotternish landslip, the longest such feature in Great Britain. It is the type locality for the mineral gyrolite.
The area in front of the cliffs of the Storr is known as the Sanctuary. This has a number of weirdly shaped rock pinnacles, the remnants of ancient landslips.
Ascent routes.
A well-constructed path, used by many sightseers, leaves the A855 just north of Loch Leathan. It heads up through a clearfell area that was formerly a conifer plantation. Most day-trippers are content simply to wander around the Sanctuary, admiring the pinnacles and gazing up at the Storr's eastern cliffs. Walkers can easily ascend to the summit, however, by skirting below the cliffs whilst heading north from the north end of the Sanctuary. After passing over a fence at a makeshift stile and climbing a brief steep section of loose rock, the recommended route for walkers heads north-west as far as Coire Scamadal, 1 km north of the summit, then doubles back and heads southwards along the north side, climbing towards the summit. From this route, visible breaks in the cliffs offer tempting short cuts, but these are steep, may not save time and may not be safe. An alternative route, involving some mild scrambling, follows the rim of the south-east-facing cliffs from the top of the aforementioned steep section.
Another route to or from the summit starts south-west of the car park and heads north-west to Bealach Beag, about south-west of the summit, following the course of a stream which breaches the cliffs. A steep section of this course is slippery and requires care.
The Storr is often climbed as part of a much longer expedition, following the full length of the Trotternish landslip.
Media and the arts.
From 1 August to 17 September 2005 one of Britain's single largest environmental artworks was staged on the walk up to Coire Faoin at the base of the Old Man of Storr and the Storr cliffs. Created by NVA, a Scottish environmental arts company, directed by Angus Farquhar (formerly of Test Dept) and designed by a team including "<slight>" and David Bryant from Midnight Design, the work contained music by Geir Jenssen, Paul Mounsey, live performance by Gaelic singer Anne Martin and recordings of the works of Gaelic poet Somhairle MacGill-Eain (Sorley MacLean). This was David Bryant's last major environmental creative work as he died from cancer in 2007. He won a Plasa Lighting Design award in 2006 for his work lighting the Storr.
In October 2009, a photograph taken of the pinnacles looking towards Raasay and South Rona won the "Take a view: Landscape photo of the year 2009".
In January 2012, production of the science-fiction film "Prometheus" moved to the Isle of Skye, with filming taking place at the Old Man of Storr.
British composer Matthew Taylor composed the orchestral piece "Storr", which takes its name and inspiration from the rock formation, which the composer found awe-inspiring on a visit there. "Storr" was commissioned and premièred by the Essex Symphony Orchestra conducted by Tom Hammond, and given its London première by the Kensington Symphony Orchestra and Russell Keable on 24 June 2013.


Doberg Formation

The Doberg Formation is a geologic formation in Germany. It preserves fossils dating back to the Paleogene period.


Clemville Formation

The Clemville Formation is a geologic formation in Quebec. It preserves fossils dating back to the Silurian period.


Harper Ranch Formation

The Harper Ranch Formation is a geologic formation in British Columbia. It preserves fossils dating back to the Permian period.


Melanie Leng

Melanie Jane Leng is a Professor of Isotope Geosciences at the University of Nottingham working on isotopes, palaeoclimate and geochemistry. She also serves as the Chief Scientist for Environmental Change Adaptation and Resilience at the British Geological Survey and Director of the Centre for Environmental Geochemistry, a collaboration between the University of Nottingham and the British Geological Survey. For many years (till 2019) she has been the UK convenor and representative of the UK geoscience community on the International Continental Scientific Drilling Program.
Early life and education.
Leng grew up in Scarborough, North Yorkshire. She spent her childhood on the cliffs and beaches of the Lower Jurassic. Leng studied geology for GCSE and A Level. At Sixth Form College she took a field trip to Ravenscar and described finding an ammonite which hooked her into geology. She studied for a BSc in Earth Science at Oxford Polytechnic, gained her PhD at Aberystwyth University in 1990, then moved to the British Geological Survey to work in the isotope laboratory.
Research and career.
Leng has several roles, her most current is Chief Scientist for Environmental Change Adaptation and Resilience at the British Geological Survey. She is also Director of the Centre for Environmental Geochemistry, a collaboration between the British Geological Survey and the University of Nottingham, Leng leads research around environmental change, human impact, food security, and resource management. Leng has been involved in deep drilling as part of the International Continental Scientific Drilling Program, and worked in Lake Ohrid in Macedonia and Lake Chala in East Africa. She also heads the Stable Isotope Facility at the British Geological Survey, which is part of the National Environmental Isotope Facility. Stable isotopes can be used to better understand climate change and human-landscape interactions, with increasing importance on the Anthropocene and the modern calibration period; tracers of modern pollution; and understanding the hydrological cycle especially in areas suffering human impact. Leng takes part in expeditions, most recently the Natural Environment Research Council (NERC) mission called Ocean Regulation of Climate by Heat and Carbon Sequestration and Transports (ORCHESTRA). She actively blogs about her research.
Leng serves on the editorial board of the journals "Quaternary Research", "Quaternary Science Reviews", "Scientific Reports" and the "Journal of Paleolimnology".
She has written several articles about successfully undertaking a PhD.
Awards and honours.
Leng was appointed a Member of the Order of the British Empire (MBE) in the 2019 Birthday Honours.


Bedrock Spring Formation

The Bedrock Spring Formation is a geologic formation in California. It preserves fossils dating back to the Neogene period.


Patrick Cordier (mineralogist)

Patrick Cordier (born February 1, 1961) is a mineralogist who uses experimental and numerical approaches to study the plasticity of geological materials. He has authored or co-authored over 200 articles in international scientific journals. He received the Dana Medal from the Mineralogical Society of America in 2016, and is currently a chief editor of the "European Journal of Mineralogy". and a member of"Institut Universitaire de France".
Education.
Cordier obtained a master's degree in materials science in 1985 from the School of Engineers of Lille (EUDIL), and a DEA from the University of Lille 1 in materials science. He completed a doctoral thesis on the plasticity of quartz, directed by Professor Jean-Claude Doukhan, at the University of Lille 1 in 1989.
Early career.
In 1989, Cordier worked as post-doctoral scientist with Professor Arthur Heuer (Department of Materials Science and Engineering, Case School of Engineering, Cleveland, USA). The same year, he joined the University of Lille 1 as an assistant professor. He passed his habilitation to lead scientific research in 1995 at Lille, and became an associate professor of physics in 1996. At the 'Unité Materiaux Transformations' research institute of the University of Lille, he led the research group for Mineral Physics from 1999 to 2017, and the research group for Plasticity from 2017 to 2020.
Current research.
Cordier is a specialist in transmission electron microscopy and has devoted himself particularly to the study of crystal defects such as dislocations and the plasticity of minerals. In particular, he studies the plasticity of the high-pressure mineral phases of the Earth's mantle. With Philippe Carrez, he is currently developing an approach to this problem based on multi-scale numerical modelling.
He has regularly visited at the Bayerisches Geoinstitut (Bayreuth, Germany) at the University of Bayreuth since 1998 to carry out deformation experiments at very high pressures and is presently a visiting professor at the Institute of Mechanics, Materials and Civil Engineering of the Université Catholique de Louvain, Belgium.
Honors.
Cordier has received French recognition for distinguished service in education (Ordre des Palmes Académiques, Chevalier in 2008; Officier in 2013), and the Grand Prix Frédéric Kuhlmann of the Société des Sciences, de l’Agriculture et des Arts de Lille (SSAAL) in 2015.
He has also been a fellow of the Mineralogical Society of America since 2008 and received the Dana Medal from them in 2016.
In 2019, he became the first French fellow of the American Geophysical Union in the focus group 'Mineral and Rock Physics'. The same year he was elected at Institut Universitaire de France as a senior member.
He is the current president (2018–2020) of the International Mineralogical Association (IMA). He has also served as the first vice-president (2016–2018) of the IMA, and the vice-president (2004–2007) and president (2008–2009) of the French Mineralogical Society (Société Française de Minéralogie et Cristallographie).
He has twice received ERC-Adv grants, for the projects RheoMan (2011–2017) and TimeMan (2018–2022).


Roca Formation (United States)

The Roca Formation (or Roca Shale) is an early Permian geologic formation (Wolfcampian) with its exposure running north and south through Kansas and extending into Nebraska and Oklahoma, notably comprising varicolored black, brown, gray, green, red, and blue shales, mudstones, and limestone, some of which representing Permian paleosols.


Pendeloque

A pendeloque is a pear-shaped modification of the round brilliant cut used for diamonds and other gemstones.