concretions definition


Minerals & Geology Index Page By signing in, you agree to our Terms and Conditions Although often rounded, concretions can be lumpy, long, oval, disk-shaped, or irregular. of the gel and infilling of shrinkage cracks (Franks, 1969). Sandstone "logs" are elongate sand bodies that have been They often form an erosion-resistant The outer part of the Moeraki boulders erodes to reveal the inner septarian veins of calcite, which grew outward from a hollow core. Concretions in beds of conglomeratic sediment (sediment containing gravel or cobbles) look like a conglomerate, but they may be in loose lithified surroundings. Last 300 years. paleocurrent directions in associated channel sand bodies, Parsons (1980) In mineralogy, a concretion is a mineral mass formed by precipitation. Another major concretion outcrop occurs along 500 feet of Lake Huron at Kettle Point in southern Ontario. Large spherical concretions erode from mudstone cliffs at Moeraki, on New Zealand's South Island. in the Cannonball and Fox Hills Formations in Morton and Sioux counties How to use a word that (literally) drives some pe Editor Emily Brewster clarifies the difference. Over time, a concretionmay weather out when the softer rock surrounding it erodes away. The word "concretion" is derived from the Latin "con"-- meaning "together" -- and "cresco" -- meaning "to grow." This large concretion in Montana has protected the softer material beneath it from erosion, resulting in a classic hoodoo. These Montana concretions eroded from the sand beds behind them. Subscribe to America's largest dictionary and get thousands more definitions and advanced searchad free! mendhak, by sa 3.0, 2001-2022 Futura-Sciences, all rights reserved - MadeInFutura - Futura-Sciences en franais. variety in North Dakota. of iron oxides are common on clay particles. that the nodules formed contemporaneously with sedimentation (Frye, of the buttes of southwestern North Dakota. Bedding They vary in color, hardness, and sizefrom smaller than the head of a pin to several hundred poundsand are sometimes misidentified as fossils, dinosaur eggs, or meteorites. part of a regressive, marginal marine sequence. Being more firmly cemented than the enclosing sandstone, concretions weather out in myriad shapes, that have been fancifully described as cannonballs, pumpkins, dinosaur limbs or bric-a-brac. by Penguin Random House LLC and HarperCollins Publishers Ltd, Example sentences from the Collins Corpus. Descriptions dating from the 18th century attest to the fact that concretions have long been regarded as fascinating geologic curiosities.

sediments often have more clay, chert, and volcanic materials. In addition, conditions of photic zone euxinia are often found to occur during concretion 84 p. Jacob, Arthur F., 1973, Elongate Concretions as Paleochannel Indicators, (2020, August 27). lagoons, perhaps as a gel. These can range from sand crystals or barite roses to spheroidal or discoidal concretions tens of metres across. The outer surfaces of these concretions may also be covered by shallow indentations similar to the surface of a golf ball. A daily challenge for crossword fanatics. Most often the cementing mineral is calcite, but the brown, iron-bearing carbonate mineral siderite is also common. bedding around the nodules, and soft sediment deformation -indicates Concretions from the Marcellus Shale near Bethany, New York. Sign up to make the most of YourDictionary. That is, 2022 LoveToKnow Media. though of different composition than the sediments that contain them. In a detailed study of elongate concretions in Adams County, The bumps on the right-hand one are fossil shells; planes on the left-hand one are fissure fillings. Concretions are masses of mineral matter embedded within rock layers, including limestone, sandstone, and shale. and an important ore of iron in many parts of the world. This appears to have grown as a soft mineral gel. Fossiliferous Concretions relative sea level rise, and finally continued progradation of deltaic They are common though not abundant Examples include fossiliferous concretions of the underlying Fox Hills . Read our series of blogs to find out more. Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. We look at some of the ways in which the language is changing. different than what surrounds them. suggests that they have been partially or totally replaced by cementation, Siderite or "ironstone" nodules are heavy, dark brownish Like Amaze your friends with your new-found knowledge! . soft, complex mixtures of iron oxides and hydroxides. , 'Fossilised Biomolecules and Biomarkers in Carbonate Concretions from Konservat-Lagersttten', He fell through the window, causing the glass to, https://creativecommons.org/licenses/by-sa/4.0/legalcode. of America Bulletin, v.84, p. 2127-2132. Large ironstone (ferruginous) concretions in Jurassic rocks of Laig Bay in Isle of Eigg, Scotland. The cementing agent in these concretions is a combination of carbonate and silica. weathered rind, nodules are dark purplish black in color, probably due Sign up below or read more about the DesertUSA newsletter here. be just an intermediate stage of complete lithification of an entire They are especially common and Interior of a pod-shaped ferruginous concretion that formed in shale of Eocene age in Oakland, California. Large, irregular concretions in the Scalby Formation (Middle Jurassic age) at Burniston Bay near Scarborough, U.K. The knife handle is 8 centimeters long. cemented, principally by calcium carbonate, to form log-like concretions Oil Comes from Dinosaurs - Fact or Fiction? Last 50 years large, spherical sandstone concretions.

sediments and bedrock formations that occur in the eastern half of the

Updates? such as would be the case for more flattened or irregularly shaped concretions. Concretions are universal, yet every one is different, especially when they depart from spheroid forms. This locality is near Point Arena, part of Schooner Gulch State Beach. Fossiliferous, carbonate-cemented concretions of the Upper Cretaceous Send us feedback. They vary widely in shape and size, with the huge spherical concretions at Rock City in Ottawa County and Mushroom Rock State Park in Ellsworth County measuring up to 27 feet in diameter. A concretion is a solid foreign body that forms in tissue or in an organ, such as gallstones or kidney stones, and sodium urate tophus. But they can also be composed of other sedimentary minerals that include dolomite, ankerite, siderite, pyrite, barite and gypsum, to name a few. Concretions may be quite fragile. rounded forms, to thin beds tens of feet long. They create white water rapids in the Athabasca River.

These concretions are typically spheres to oblate spheroids, ranging in size from 1 to 5 feet in diameter. Franks, P.C., 1969, Synaeresis features and genesis of siderite concretions, These concretions vary from realistic rounded, flattened, or cylindrical forms to imaginative shapes with imposing names like botryoidal (bunch of grapes), fusiform (like a spindle), and ameboid (of the microscopic creature). Concretions often assume organic shapes, which catch people's eyes. This photo was posted in the Geology Forum. changes in trace element and isotopiccompositions between successive Periods and systems? cholelithiasis definition Study guides for every stage of your learning journey. in the Cretaceous Hell Creek Formation.

Formation, south-western North Dakota: Unpublished UND M.S. borrowed from Latin concrtin-, concrti "formation into something solid," from concr-, stem of concrscere "to coalesce, condense, solidify, harden" + -tin-,-ti, suffix of verbal action more at concrescence. Many geologists, for example, Groenewold (1971) and Jacob (1973), have Improve your English with Collins. Get the latest news and gain access to exclusive updates and offers. concretion (countable and uncountable, plural concretions), Definition from Wiktionary, the free dictionary, process of aggregating or coalescing into a mass, action of making something concrete or the result of such an action, Of the three beds, the central one is the most compact, and more like ordinary sandstone: it includes numerous flattened spherical, "My new statue!" and can be found in badland areas farther west, (Perhaps cannonballs resulted from solidification of an iron-carbonate gel. All rights reserved. sand bed. A concretion is a compact mass of mineral matter, usually spherical or disk-shaped, embedded in a host rock of a different composition. . Concretions weather out of steeply tilted mudstone of Cenozoic age. Good examples can be seen in the upper reaches of Arroyo Tapiado (Spanish word for "Concretion Wash"), in the depths of Arroyo Seco del Diablo, Cannonball Wash and the famous Pumpkin Patch. and associated channels. of many siderite nodules may have resulted from the solidification (dewatering) Kiowas Formation (Early Cretaceous), north-central Kansas: Journal of They are most easily seen in areas of badland variety of concretions and nodules found in North Dakota, such a scheme to dark brown limonite, a "catch-all" name for relatively Concretions in Kansas are formed from any of a number of minerals, including calcite, limonite, barite, pyrite, and silica.

Because of the variety of unusual shapes, sizes and compositions, concretions have been variously interpreted to be dinosaur eggs, animal and plant fossils (called pseudofossils), extra-terrestrial debris or human artifacts. Area 51, Starship, and Harvest Moon: Septembers Words in the News. Concretions at Bowling Ball Beach erode out of their sedimentary matrix. Mineral mass formed by precipitation around a fragment of material. The term comes from Accessed 22 Jul. I find concretions and nodules interesting precisely because they are The iron cement includes the amorphous oxide mixture limonite. North Dakota, Parsons (1980) found that sandstone "logs" may black nodules that occur as small isolated spheres, through complex This pattern of ridges and raised welts may have Im sure a lot of people would agree that we live in strange times. Alden, Andrew. Test your vocabulary with our 10-question quiz! Cannonballs Concretions most often form in sediment before or as the sediment is compacted into rock, but they also can form in hardened sedimentary rock when minerals in groundwater are deposited in rock pores and cavities. The raised welts at the center of some polygons Although there is no comprehensive classification scheme for the great understand the configuration of ancient streams and landscapes). noted that the long axis of the "logs" lies parallel to bedding Most are oval in cross-section, growth parallel to the direction of paleo-groundwater flow. When the concretion is exposed to weathering, the softer parts between the calcite-filled cracks erode. Copyright 2002 North Dakota Geological Survey and to the axis of the channel sands in which they are found. And whats this about fish the look like aliens. Thesaurus: All synonyms and antonyms for concretion, Britannica.com: Encyclopedia article about concretion. responsible for concretion formation, Carpenter et al. Photo courtesy Ken Turnbull, Denver, Colorado. Let us know if you have suggestions to improve this article (requires login). Concretion is a term used in the fields of biology and mineralogy. Photo courtesy Ken Turnbull, Denver, Colorado, Courtesy Terry Wright, all rights reserved, Eroded Concretions at Moeraki, New Zealand. Eons and eonothems? Concretions and nodules are found in all of the geologic formations

They are commonly composed of a carbonate mineral such as calcite, but sometimes an iron oxide or hydroxide such as goethite or sometimes an amorphous or microcrystalline form of silica about a nucleus. Formation and even older Pierre Formation, marcasite or pyrite nodules Last modified: This small cylindrical concretion formed around the trace of a plant root in shale of Miocene age from Sonoma County, California. Since Exist The source Underneath the formations and are typically 1 to 3 meters (3 to 9 feet) in diameter They are seldom greater than two to three feet in diameter. They often take shapewhen minerals precipitating (settling) out of water collect around a nucleus, such as a pebble, leaf, shell, bone, or fossil. Concretions can be shaped like cylinders, sheets, nearly perfect spheres, and everything in between.
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