|
Moeraki Boulders
The Moeraki Boulders (officially Moeraki Boulders / Kaihinaki) are unusually large spherical boulders lying along a stretch of Koekohe Beach on the wave-cut Otago coast of New Zealand between Moeraki and Hampden. They occur scattered either as isolated or clusters of boulders within a stretch of beach where they have been protected in a scientific reserve. These boulders are grey-coloured septarian concretions, which have been exhumed from the mudstone and bedrock enclosing them and concentrated on the beach by coastal erosion.Boles, J. R., C. A. Landis, and P. Dale, 1985''The Moeraki Boulders; anatomy of some septarian concretions'' Journal of Sedimentary Petrology, vol. 55, n. 3, p. 398-406.Fordyce, E., and P. Maxwell, 2003, ''Canterbury Basin Paleontology and Stratigraphy, Geological Society of New Zealand Annual Field Conference 2003 Field Trip 8'', Miscellaneous Publication 116B, Geological Society of New Zealand, Dunedin, New Zealand. Forsyth, P.J., and G. Coates, 1992, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mosasaur
Mosasaurs (from Latin ''Mosa'' meaning the 'Meuse', and Ancient Greek, Greek ' meaning 'lizard') are an extinct group of large aquatic reptiles within the family Mosasauridae that lived during the Late Cretaceous. Their first fossil remains were discovered in a limestone quarry at Maastricht on the Meuse in 1764. They belong to the order Squamata, which includes lizards and snakes. During the last 20 million years of the Cretaceous period (Turonian–Maastrichtian ages), with the extinction of the ichthyosaurs and Pliosauridae, pliosaurs, mosasaurids became the dominant marine predators. They themselves became extinct as a result of the Cretaceous–Paleogene extinction event, K-Pg event at the end of the Cretaceous period, about 66 million years ago. Description Mosasaurs breathed air, were powerful swimmers, and were well-adapted to living in the warm, shallow Inland sea (geology), inland seas prevalent during the Late Cretaceous period. Mosasaurs were so well adapted to thi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kimmeridge Clay
The Kimmeridge Clay is a sedimentary rock, sedimentary deposit of fossiliferous marine clay which is of Late Jurassic to lowermost Cretaceous age and occurs in southern and eastern England and in the North Sea. This rock formation (geology), formation is the major source rock for North Sea oil. The fossil fauna of the Kimmeridge Clay includes turtles, crocodiles, Sauropoda, sauropods, Plesiosauria, plesiosaurs, Pliosauroidea, pliosaurs and ichthyosaurs, as well as a number of invertebrate species. Description Kimmeridge Clay is named after the village of Kimmeridge on the Dorset coast of England, where it is well exposed and forms part of the Jurassic Coast World Heritage Site. Onshore, it is of Late Jurassic (Kimmeridgian) age and outcrops across England, in a band stretching from Dorset in the south-west, north-east to North Yorkshire. Offshore, it extends into the Lower Cretaceous (Berriasian Stage) and it is found throughout the Southern, Central and Northern North Sea. Th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sedimentary
Sedimentary rocks are types of rock formed by the cementation of sediments—i.e. particles made of minerals (geological detritus) or organic matter (biological detritus)—that have been accumulated or deposited at Earth's surface. Sedimentation is any process that causes these particles to settle in place. Geological detritus originates from weathering and erosion of existing rocks, or from the solidification of molten lava blobs erupted by volcanoes. The geological detritus is transported to the place of deposition by water, wind, ice or mass movement, which are called agents of denudation. Biological detritus is formed by bodies and parts (mainly shells) of dead aquatic organisms, as well as their fecal mass, suspended in water and slowly piling up on the floor of water bodies ( marine snow). Sedimentation may also occur when dissolved minerals precipitate from water solution. The sedimentary rock cover of the continents of the Earth's crust is extensive (73% of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Concretions
A concretion is a hard and compact mass formed by the precipitation of mineral cement within the spaces between particles, and is found in sedimentary rock or soil. Concretions are often ovoid or spherical in shape, although irregular shapes also occur. The word ''concretion'' is borrowed from Latin , itself derived from ''concrescere'' , from ''con-'' and ''crescere'' . Concretions form within layers of sedimentary Stratum, strata that have already been deposited. They usually form early in the burial history of the sediment, before the rest of the sediment is hardened into rock. This concretionary cement often makes the concretion harder and more resistant to weathering than the host stratum. There is an important distinction to draw between concretions and Nodule (geology), nodules. Concretions are formed from mineral precipitation around some kind of nucleus while a nodule is a replacement body. Descriptions dating from the 18th century attest to the fact that concreti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quartz
Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The Atom, atoms are linked in a continuous framework of SiO4 silicon–oxygen Tetrahedral molecular geometry, tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical formula of Silicon dioxide, SiO2. Quartz is, therefore, classified structurally as a Silicate mineral#Tectosilicates, framework silicate mineral and compositionally as an oxide mineral. Quartz is the second most abundant mineral in Earth's continental crust, behind feldspar. Quartz exists in two forms, the normal α-quartz and the high-temperature β-quartz, both of which are chiral. The transformation from α-quartz to β-quartz takes place abruptly at . Since the transformation is accompanied by a significant change in volume, it can easily induce microfracturing of ceramics or rocks passing through this temperature threshold. There are many different varieties of quartz, several of which are classifi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dolomite (mineral)
Dolomite () is an anhydrous carbonate mineral composed of calcium magnesium carbonate, ideally The term is also used for a sedimentary carbonate rock composed mostly of the mineral dolomite (see Dolomite (rock)). An alternative name sometimes used for the dolomitic rock type is dolostone. History As stated by Nicolas-Théodore de Saussure the mineral dolomite was probably first described by Carl Linnaeus in 1768. In 1791, it was described as a rock by the French natural history, naturalist and geologist Déodat Gratet de Dolomieu (1750–1801), first in buildings of the old city of Rome, and later as samples collected in the County_of_Tyrol, Tyrolean Alps. Nicolas-Théodore de Saussure first named the mineral (after Dolomieu) in March 1792. Properties The mineral dolomite crystallizes in the trigonal, trigonal-rhombohedral system. It forms white, tan, gray, or pink crystals. Dolomite is a double carbonate, having an alternating structural arrangement of calcium and magnesium ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Scalenohedron
In geometry, a bipyramid, dipyramid, or double pyramid is a polyhedron formed by fusing two pyramids together base-to-base. The polygonal base of each pyramid must therefore be the same, and unless otherwise specified the base vertices are usually coplanar and a bipyramid is usually ''symmetric'', meaning the two pyramids are mirror images across their common base plane. When each apex (, the off-base vertices) of the bipyramid is on a line perpendicular to the base and passing through its center, it is a ''right'' bipyramid; otherwise it is ''oblique''. When the base is a regular polygon, the bipyramid is also called ''regular''. Definition and properties A bipyramid is a polyhedron constructed by fusing two pyramids which share the same polygonal base; a pyramid is in turn constructed by connecting each vertex of its base to a single new vertex (the apex) not lying in the plane of the base, for an gonal base forming triangular faces in addition to the base face. An gona ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Calcite
Calcite is a Carbonate minerals, carbonate mineral and the most stable Polymorphism (materials science), polymorph of calcium carbonate (CaCO3). It is a very common mineral, particularly as a component of limestone. Calcite defines hardness 3 on the Mohs scale of mineral hardness, based on Scratch hardness, scratch hardness comparison. Large calcite crystals are used in optical equipment, and limestone composed mostly of calcite has numerous uses. Other polymorphs of calcium carbonate are the minerals aragonite and vaterite. Aragonite will change to calcite over timescales of days or less at temperatures exceeding 300 °C, and vaterite is even less stable. Etymology Calcite is derived from the German , a term from the 19th century that came from the Latin word for Lime (material), lime, (genitive ) with the suffix ''-ite'' used to name minerals. It is thus a Doublet (linguistics), doublet of the word ''wikt:chalk, chalk''. When applied by archaeology, archaeologists and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electron Microprobe
An electron microprobe (EMP), also known as an electron probe microanalyzer (EPMA) or electron micro probe analyzer (EMPA), is an analytical tool used to non-destructively determine the chemical composition of small volumes of solid materials. It works similarly to a scanning electron microscope: the sample is bombarded with an electron beam, emitting x-rays at wavelengths characteristic to the elements being analyzed. This enables the abundances of elements present within small sample volumes (typically 10-30 cubic micrometers or less) to be determined,Wittry, David B. (1958). "Electron Probe Microanalyzer"US Patent No 2916621 Washington, DC: U.S. Patent and Trademark Office when a conventional accelerating voltage of 15-20 kV is used. The concentrations of elements from lithium to plutonium may be measured at levels as low as 100 parts per million (ppm), material dependent, although with care, levels below 10 ppm are possible. The ability to quantify lithium by EPMA became a re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
X-ray Crystallography
X-ray crystallography is the experimental science of determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to Diffraction, diffract in specific directions. By measuring the angles and intensities of the X-ray diffraction, a crystallography, crystallographer can produce a three-dimensional picture of the density of electrons within the crystal and the positions of the atoms, as well as their chemical bonds, crystallographic disorder, and other information. X-ray crystallography has been fundamental in the development of many scientific fields. In its first decades of use, this method determined the size of atoms, the lengths and types of chemical bonds, and the atomic-scale differences between various materials, especially minerals and alloys. The method has also revealed the structure and function of many biological molecules, including vitamins, drugs, proteins and nucleic acids such as DNA. X-ray crystall ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Optical Mineralogy
Optical mineralogy is the study of minerals and Rock (geology), rocks by measuring their optics, optical properties. Most commonly, rock and mineral samples are prepared as thin sections or grain mounts for study in the laboratory with a petrographic microscope. Optical mineralogy is used to identify the mineralogical composition of geological materials in order to help reveal their origin and evolution. Some of the properties and techniques used include: * Refractive index * Birefringence * Auguste Michel-Lévy, Michel-Lévy Interference colour chart * Pleochroism * Extinction angle * Conoscopic interference pattern (Interference figure) * Becke line test * Optical relief * Sign of elongation (Length fast vs. length slow) * Wave plate History William Nicol (inventor), William Nicol, whose name is associated with the creation of the Nicol prism, is likely the first to prepare thin slices of mineral substances, and his methods were applied by Henry Thronton Maire Witham (1831) t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
