A concretion is a volume of sedimentary rock in which a mineral cement fills the porosity (i. Sedimentary rock is one of the three main rock types (the others being igneous and Metamorphic rock) A mineral is a naturally occurring substance formed through geological processes that has a characteristic chemical composition a highly ordered atomic structure and specific e. the spaces between the sediment grains). Concretions are often ovoid or spherical in shape, although irregular shapes also occur. The word 'concretion' is derived from the Latin con meaning 'together' and cresco meaning 'to grow'. Latin ( lingua Latīna, laˈtiːna is an Italic language, historically spoken in Latium and Ancient Rome. Concretions form within layers of sedimentary strata that have already been deposited. In Geology and related fields a stratum (plural strata) is a layer of rock or Soil with internally consistent characteristics that distinguishes 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. Weathering is the decomposition of earth rocks, Soils and their Minerals through direct contact with the planet's Atmosphere. In Geology and related fields a stratum (plural strata) is a layer of rock or Soil with internally consistent characteristics that distinguishes
Descriptions dating from the 18th century attest to the fact that concretions have long been regarded as geological curiosities. The 18th century lasted from 1701 to 1800 in the Gregorian calendar, in accordance with the Anno Domini / Common Era numbering system Because of the variety of unusual shapes, sizes and compositions, concretions have been interpreted to be dinosaur eggs, animal and plant fossils (called pseudofossils), extraterrestrial debris or human artifacts. FOSSIL is a standard protocol for allowing serial communication for Telecommunications programs under the DOS Operating system. Pseudofossils are Inorganic objects markings or impressions that might be mistaken for Fossils Pseudofossils may be misleading as some types of mineral deposits In Archaeology, an artifact or artefact is any object made or modified by a human culture, and often one later recovered by some archaeological
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Origins
Detailed studies (i. e. , Boles et al. , 1985; Thyne and Boles, 1989; Scotchman, 1991; Mozley and Burns, 1993; McBride et al. , 2003; Chan et al. , 2005; Mozley and Davis, 2005) published in peer-reviewed journals, have demonstrated that they form subsequent to burial during diagenesis. In Geology and Oceanography, diagenesis is any chemical physical or biological change undergone by a Sediment after its initial deposition and during They quite often form by the precipitation of a considerable amount of cementing material around a nucleus, often organic, such as a leaf, tooth, piece of shell or fossil. FOSSIL is a standard protocol for allowing serial communication for Telecommunications programs under the DOS Operating system. For this reason, fossil collectors commonly break open concretions in their search for fossil animal and plant specimens. One of the most unusual concretion nuclei, as documented by Al-Agha et al. (1995), are World War II military shells, bombs, and shrapnel, which are found inside siderite concretions found in an English coastal salt marsh. World War II, or the Second World War, (often abbreviated WWII) was a global military conflict which involved a majority of the world's nations, including A shell is a payload-carrying Projectile, which as opposed to shot, contains an explosive or other filling though modern usage includes large solid projectiles A bomb is any of a range of devices that typically rely on the Exothermic Chemical reaction of an Explosive material to produce an extremely Shrapnel is the term originally applied to an anti-personnel artillery shell which carried a large number of individual bullets to the target and then ejected them forwards relying A salt marsh is a type of Marsh that is a transitional intertidal between land and salty or Brackish water (e
Depending on the environmental conditions present at the time of their formation, concretions can be created by either concentric or pervasive growth (Mozley, 1996; Raiswell and Fisher, 2000). In concentric growth, the concretion grows as successive layers of mineral accrete to its surface. This process results in the radius of the concretion growing with time. In case of pervasive growth, cementation of the host sediments, by infilling of its pore space by precipitated minerals, occurs simultaneously throughout the volume of the area, which in time becomes a concretion. Sediment is any particulate matter that can be transported by fluid flow and which eventually is deposited as a layer of solid particles on the bed or bottom of a body of
Appearance
Concretions vary in shape, hardness and size, ranging from objects that require a magnifying lens to be clearly visible to huge bodies three meters in diameter and weighing several thousand pounds. History The Quroste Ohlone Native Americans were the first people known to inhabit the Año Nuevo area The giant, red concretions occurring in Theodore Roosevelt National Park, in North Dakota, are almost 3 m (10 feet) in diameter. Established in 1978 Theodore Roosevelt National Park is a United States National Park comprising three geographically separated areas of Badlands in western North Dakota ( is a state located in the Midwestern and Western regions of the United States of America. Spheroidal concretions, as large as 9 m (30 feet) in diameter, have been found eroding out of the Qasr El Sagha Formation within the Faiyum depression of Egypt. Concretions are usually similar in color to the rock in which they are found. Concretions occur in a wide variety of shapes, including spheres, disks, tubes, and grape-like or soap bubble-like aggregates.
Composition
They are commonly composed of a carbonate mineral such as calcite; an amorphous or microcrystalline form of silica such as chert, flint, or jasper; or an iron oxide or hydroxide such as goethite and hematite. In Chemistry, a carbonate is a salt or Ester of Carbonic acid. Calcite is a carbonate mineral and the most stable polymorph of Calcium carbonate ( Ca[[carbon C]] O 3 The Chemical compound silicon dioxide, also known as silica or silox (from the Latin " Silex " is an Oxide Chert (ˈtʃɝt is a fine-grained Silica -rich Microcrystalline, Cryptocrystalline or Microfibrous Sedimentary rock that may contain Flint (or flintstone) is a hard sedimentary Cryptocrystalline form of the Mineral Quartz, categorized as a variety of Chert JasPer is a project to create a reference implementation of the codec specified in the JPEG-2000 Part-1 standard (ie Goethite, named after the German Polymath Johann Wolfgang von Goethe, is an iron bearing oxide mineral found in soil and other low temperature environments Hematite, also spelt hæmatite, is the Mineral form of Iron(III oxide (Fe2O3 one of several Iron oxides They can also be composed of other minerals that include dolomite, ankerite, siderite, pyrite, marcasite, barite and gypsum. Dolomite (ˈdɒləmaɪt is the name of a Sedimentary Carbonate rock and a Mineral, both composed Ankerite is a Calcium, Iron, Magnesium, Manganese carbonate mineral of the group of rhombohedral carbonates with formula Ca Siderite is also the name of a type of Iron Meteorite. ---- Siderite is a Mineral composed of Iron Carbonate Fe[[carbon The Mineral marcasite, sometimes called white iron pyrite, is Iron Sulfide (FeS2 Baryte ( Ba[[Sulfur S]] O 4 is a Mineral consisting of Barium sulfate. Gypsum is a very soft Mineral composed of Calcium sulfate dihydrate with the Chemical formula Ca[[sulfur S]] O 4·2
Although concretions often consist of a single dominant mineral, other minerals can be present depending on the environmental conditions which created them. For example, carbonate concretions, which form in response to the reduction of sulfates by bacteria, often contain minor, percentages of pyrite. The Bacteria ( singular: bacterium) are a large group of unicellular Microorganisms Typically a few Micrometres in length bacteria have Other concretions, which formed as a result of microbial sulfate reduction, consist of a mixture of calcite, barite, and pyrite.
Occurrence
Concretions are found in a variety of rocks, but are particularly common in shales, siltstones, and sandstones. Emery is a town in Emery County, Utah, United States. The population was 308 at the 2000 census. Shale (also called mudstone) is a fine-grained Sedimentary rock whose original constituents were Clay minerals or Muds It is characterized by Siltstone is a Sedimentary rock which has a composition intermediate in grain size between the coarser Sandstones and the finer Mudstones and Sandstone is a Sedimentary rock composed mainly of Sand -size Mineral or rock grains. They often outwardly resemble fossils or rocks that look as if they do not belong to the stratum in which they were found. Occasionally, concretions contain a fossil, either as its nucleus or as a component that was incorporated during its growth but concretions are not fossils themselves. They appear in nodular patches, concentrated along bedding planes, protruding from weathered cliffsides, randomly distributed over mudhills or perched on soft pedestals.
Small hematite concretions ("blueberries") have been observed on Mars. See Martian spherules. Martian spherules (also known as blueberries due to their blue hue in false-color images released by NASA are the abundant spherical hematite inclusions discovered by the
Types of concretions
Some of the names of concretions are septarian concretions, cannonball concretions, Moqui (Moki) marbles, and pop rocks.
Septarian concretions
Septarian concretions or septarian nodules, are concretions containing angular cavities or cracks, which are called "septaria". The word comes from the Latin word septum; "partition", and refers to the cracks/separations in this kind of rock[1]. Latin ( lingua Latīna, laˈtiːna is an Italic language, historically spoken in Latium and Ancient Rome. There is an incorrect explanation that it comes from the Latin word for "seven", septem[2], referring to the number of cracks that commonly occur.
The process which created the septaria, which characterize septarian concretions, remains a mystery. A number of mechanisms, i. e. the dehydration of clay-rich, gel-rich, or organic-rich cores; shrinkage of the concretion's center; expansion of gases produced by the decay of organic matter; brittle fracturing of the concentration by either earthquakes or compaction; and others, have been proposed for the formation of septaria. At this time, it is uncertain, which, if any, of these and other proposed mechanisms is responsible for the formation of septaria in septarian concretions (McBride et al. 2003). Septaria usually contain crystals precipitated from circulating solutions, usually of calcite. Siderite or pyrite coatings are also occasionally observed on the wall of the cavities present in the septaria, giving rise respectively to a panoply of bright reddish and golden colors. Some septaria may also contain small calcite stalagtites and well-shaped millimetric pyrite single crystals.
A spectacular example of septarian concretions, which are as much as 3 meters (9 feet) in diameter, is the Moeraki Boulders. The Moeraki Boulders are unusually large and spherical boulders lying along a stretch of Koekohe Beach on the wave cut Otago coast of New Zealand between These concretions are found eroding out of Paleocene mudstone of the Moeraki Formation exposed along the coast near Moeraki, South Island, New Zealand. The Paleocene or Palaeocene, "early dawn of the recent" is a geologic epoch that lasted from 65 Moeraki is a small fishing village on the east coast of the South Island of New Zealand. The South Island is the larger of the two major islands of New Zealand, the other being the more populous North Island. New Zealand is an Island country in the south-western Pacific Ocean comprising two main landmasses (the North Island and the South Island They are composed of calcite-cemented mud with septarian veins of calcite and rare late-stage quartz and ferrous dolomite (Boles et al. 1985, Thyne and Boles 1989). Very similar concretions, which are as much as 3 meter (9 feet) in diameter and called "Koutu Boulders", litter the beach between Koutu and Kauwhare points along the south shore of the Hokianga Harbour of Hokianga, North Island, New Zealand. The Hokianga Harbour, also known as The Hokianga River or more frequently simply as The Hokianga is a long estuarine drowned valley and its surrounding area on the The North Island is one of the two main islands of New Zealand, the other being the South Island. The much smaller septarian concretions found in the Kimmeridge Clay exposed in cliffs along the Wessex Coast of England are more typical examples of septarian concretions (Scotchman 1991). The Kimmeridge Clay Formation is arguably the most economically important unit of rocks in the whole of Europe being the major Source rock for oil fields in the North England is a Country which is part of the United Kingdom. Its inhabitants account for more than 83% of the total UK population whilst its mainland
Cannonball concretions
Cannonball concretions are large spherical concretions, which resemble cannonballs. These are found along the Cannonball River within Morton and Sioux Counties, North Dakota, and can reach 3 m (10 feet) in diameter. The Cannonball River is a tributary of the Missouri River, approximately 135 mi (217 km long in southwestern North Dakota in the United States. North Dakota ( is a state located in the Midwestern and Western regions of the United States of America. They were created by early cementation of sand and silt by calcite. Calcite is a carbonate mineral and the most stable polymorph of Calcium carbonate ( Ca[[carbon C]] O 3 Similar cannonball concretions, which are as much as 4 to 6 m (12 to 18 feet) in diameter, are found associated with sandstone outcrops of the Frontier Formation in northeast Utah and central Wyoming. The State of Utah (ˈjuːtɔː or) is a western state of the United States. The State of Wyoming ( is a sparsely populated state in the western region of the United States. They formed by the early cementation of sand by calcite (McBride et al. 2003). Somewhat weathered and eroded giant cannonball concretions, as large as 6 meters (18 feet) in diameter, occur in abundance at "Rock City" in Ottawa County, Kansas. Rock City is a park located on hillsides overlooking the Solomon River in Ottawa County Kansas. Ottawa County (standard abbreviation OT) is a county located in the U The Moeraki and Koutu boulders of New Zealand are example of septarian concretions, which are also cannonball concretions. Large spherical rocks, which are found on the shore of Lake Huron near Kettle Point, Ontario, and locally known as "kettles", are typical cannonball concretions. Lake Huron, bounded on the west by the US state of Michigan, and on the east by the province of Ontario, Canada, is one of the five Great Kettle Point 44 is an Indian reserve 35 km northeast of Sarnia Ontario on the southern shore of Lake Huron Cannonball concretions have also been reported from Van Mijenfjorden, Spitsbergen; near Haines Junction, Yukon Territory, Canada; Jameson Land, East Greenland; near Mecevici, Ozimici, and Zavidovici in Bosnia-Herzegovina; and many other places. Spitsbergen (formerly known as West Spitsbergen, and sometimes misspelled Spitzbergen) is a Norwegian island the largest Island of the Country to "Dominion of Canada" or "Canadian Federation" or anything else please read the Talk Page Greenland (Kalaallit Nunaat meaning "Land of the Greenlanders" Grønland is a self-governing Danish Province located between the Reports of cannonball concretions have also come from Bandeng and Zhanlong hills near Gongxi Town, Hunan Province, China. China ( Wade-Giles ( Mandarin) Chung¹kuo² is a cultural region, an ancient Civilization, and depending on perspective a National [3]
Elongate concretions
Elongate concretions form parallel to sedimentary strata and have been studied extensively due to the inferred influence of phreatic (saturated) zone groundwater flow direction on the orientation of the axis of elongation (e. g. , Johnson, 1989; McBride et al. , 1994; Mozley and Goodwin, 1995; Mozley and Davis, 2005). In addition to providing information about the orientation of past fluid flow in the host rock, elongate concretions can provide insight into local permeability trends (i. e. , permeability correlation structure; Mozley and Davis, 1996), variation in groundwater velocity (Davis, 1999), and the types of geological features that influence flow.
Moqui Marbles
Moqui Marbles also called Moqui balls, and "Moki marbles", are iron oxide concretions, which can found eroding in great abundance out of outcrops of the Navajo Sandstone within south-central and southeastern Utah. Navajo Sandstone is a geologic formation in the Glen Canyon Group that is spread across the U Navajo Sandstone is a geologic formation in the Glen Canyon Group that is spread across the U These concretions range in shape from spheres to discs, buttons, spiked balls, cylindrical forms, and other odd shapes. They range from pea-size to baseball-size. They were created by the precipitation of iron, which was dissolved in groundwater. These concretions are argued to be a terrestrial analogue of the Martian hematite spherules, called "blueberries" (Chan and Parry 2002, Chan et al. 2005).
Kansas Pop rocks
Kansas Pop rocks are concretions of either iron sulfide, i. e. pyrite and marcasite, or in some cases jarosite, which are found in outcrops of the Smoky Hill Chalk Member of the Niobrara Formation within Gove County, Kansas. The Mineral marcasite, sometimes called white iron pyrite, is Iron Sulfide (FeS2 Jarosite is a basic hydrous Sulfate of Potassium and Iron with a chemical formula of KFe(III3(OH6(SO42 Kansas ( is a Midwestern state in the central region of the United States of America, an area often referred to as the American " They are typically associated with thin layers of altered volcanic ash, called bentonite, which occur within the chalk comprising the Smoky Hill Chalk Member. Bentonite is an absorbent Aluminium phyllosilicate generally impure Clay consisting mostly of Montmorillonite. Chalk (ʧɔːk is a soft white porous Sedimentary rock, a form of Limestone composed of the Mineral Calcite. A few of these concretions enclose, at least in part, large flattened valves of inoceramid bivalves. Bivalves are Molluscs belonging to the class Bivalvia. They have two-part shells and typically both valves are symmetrical along the hinge line These concretions range in size from a few millimeters to as much as 0. 7 m (2. 3 ft) in length and 12 cm (0. 4 ft) in thickness. Most of these concretions are oblate spheroids shape. Other "pop rocks" are small polycuboidal pyrite concretions, which are as much as 7 cm (0. 23-foot) in diameter (Hattin 1982). These concretions are called "pop rocks" because they explode if thrown in a fire. Also, when they are either cut or hammered, they produce sparks and a burning sulfur smell.
Contrary to what has published on the Internet, none of the iron sulfide concretions, which are found in the Smoky Hill Chalk Member, were created by either the replacement of fossils or by metamorphic processes. In fact, metamorphic rocks are completely absent from the Smoky Hill Chalk Member (Hattin 1982). Metamorphic rock is the result of the transformation of an existing rock type the protolith, in a process called Metamorphism, which means "change Instead, all of these the iron sulfide concretions were created by the precipitation of iron sulfides within anoxic marine calcareous ooze after it had accumulated and before it had lithified into chalk. Pelagic sediments, also known as marine sediments, are those that accumulate in the Abyssal plain of the deep ocean far away from terrestrial sources that provide
Iron sulfide concretions, such as the Kansas Pop rocks, consisting of either pyrite and marcasite, are nonmagnetic (Hobbs and Hafner 1999). The Mineral marcasite, sometimes called white iron pyrite, is Iron Sulfide (FeS2 On the other hand, iron sulfide concretions, which either are composed of or contain either pyrrhotite or symthite, will be magnetic to varying degrees (Hoffmann, 1993). Pyrrhotite is an unusual Iron Sulfide mineral with a variable iron content Fe(1-xS (x = 0 to 0 Prolonged heating of either a pyrite or marcasite concretion will convert portions of either mineral into pyrrhotite causing the concretion to become slightly magnetic.
References
- Al-Agha, M. R. , S. D. Burley, C. D. Curtis, and J. Esson, 1995, Complex cementation textures and authigenic mineral assemblages in Recent concretions from the Linconshire Wash (east coast, UK) driven by Fe(0) Fe(II) oxidation: Journal of the Geological Society, London, v. 152, pp. 157-171.
- Boles, J. R. , C. A. Landis, and P. Dale, 1985, The Moeraki Boulders; anatomy of some septarian concretions:, Journal of Sedimentary Petrology. v. 55, n. 3, pp. 398-406.
- Chan, M. A. and W. T. Parry, 2002, 'Mysteries of Sandstone Colors and Concretions in Colorado Plateau Canyon Country PDF version, 468 KB : Utah Geological Survey Public Information Series. n. 77, pp. 1-19.
- Chan, M. A. , B. B. Beitler, W. T. Parry, J. Ormo, and G. Komatsu, 2005. Red Rock and Red Planet Diagenesis: Comparison of Earth and Mars Concretions PDF version, 3.4 MB : GSA Today, v. 15, n. 8, pp. 4-10.
- Davis, J. M. , 1999, Oriented carbonate concretions in a paleoaquifer: Insights into geologic controls on fluid flow: Water Resources Research, v. 35, p. 1705-1712.
- Hattin, D. E. , 1982, Stratigraphy and depositional environment of the Smoky Hill Chalk Member, Niobrara Chalk (Upper Cretaceous) of the type area, western Kansas: Kansas Geological Survey Bulletin 225:1-108.
- Hobbs, D. , and J. Hafnaer, 1999, Magnetism and magneto-structural effects in transition-metal sulphides: Journal of Physics: Condensed Matter, v. 11, pp. 8197-8222.
- Hoffmann, V. , H. Stanjek, and E. Murad, 1993, Mineralogical, magnetic and mössbauer data of symthite (Fe9S11) : Studia Geophysica et Geodaetica, v. 37, pp. 366-381.
- Johnson, M. R. , 1989, Paleogeographic significance of oriented calcareous concretions in the Triassic Katberg Formation, South Africa: Journal of Sedimentary Petrology, v. 59, p. 1008-1010.
- McBride, E. F. , M. D. Picard, and R. L. Folk, 1994, Oriented concretions, Ionian Coast, Italy: evidence of groundwater flow direction: Journal of Sedimentary Research, v. 64, p. 535-540.
- McBride, E. F. , M. D. Picard, and K. L. Milliken, 2003, Calcite-Cemented Concretions in Cretaceous Sandstone, Wyoming and Utah, U.S.A.: Journal of Sedimentary Research. v. 73, n. 3, p. 462-483.
- Mozley, P. S. , 1996, The internal structure of carbonate concretions: A critical evaluation of the concentric model of concretion growth: Sedimentary Geology: v. 103, p. 85-91.
- Mozley, P. S. , and Goodwin, L. , 1995, Patterns of cementation along a Cenozoic normal fault: A record of paleoflow orientations: Geology: v. 23, p 539-542.
- Mozley, P. S. , and Burns, S. J. , 1993, Oxygen and carbon isotopic composition of marine carbonate concretions: an overview: Journal of Sedimentary Petrology, v. 63, p. 73-83.
- Mozley, P. S. , and Davis, J. M. , 2005, Internal structure and mode of growth of elongate calcite concretions: Evidence for small-scale microbially induced, chemical heterogeneity in groundwater: Geological Society of America Bulletin, v. 117, 1400-1412.
- Raiswell, R. , and Q. J. Fisher, 2000, Mudrock-hosted carbonate concretions: a review of growth mechanisms and their influence on chemical and isotopic composition: Journal of Geological Society of London. v. 157, p. 239-251
- Scotchman, I. C. , 1991, The geochemistry of concretions from the Kimmeridge Clay Formation of southern and eastern England: Sedimentology. v. 38, pp. 79-106.
- Thyne, G. D. , and J. R. Boles, 1989, Isotopic evidence for origin of the Moeraki septarian concretions, New Zealand: Journal of Sedimentary Petrology. v. 59, n. 2, pp. 272-279.
See also
External links
- Dietrich, R. Martian spherules (also known as blueberries due to their blue hue in false-color images released by NASA are the abundant spherical hematite inclusions discovered by the Navajo Sandstone is a geologic formation in the Glen Canyon Group that is spread across the U The Moeraki Boulders are unusually large and spherical boulders lying along a stretch of Koekohe Beach on the wave cut Otago coast of New Zealand between Rock City is a park located on hillsides overlooking the Solomon River in Ottawa County Kansas. V. , 2002, Carbonate Concretions--A Bibliography
- Biek, B. , 2002, Concretions and Nodules in North Dakota North Dakota Geological Survey, Bismark, North Dakota.
- Epoch Times Staff, 2007, Mysterious Huge Stone Eggs Discovered in Hunan Province Epoch Times International. Photographs of large cannonball concretions recently found in Hunan Province, China.
- Everhart, M. , 2004, A Field Guide to Fossils of the Smoky Hill ChalkPart 5: Coprolites, Pearls, Fossilized Wood and other Remains Part of the Oceans of Kansas web site.
- Hansen, M. C. , 1994, Ohio Shale Concretions PDF version, 270 KB Ohio Division of Geological Survey GeoFacts n. 4, pp. 1-2.
- Hanson, W. D. , and J. M. Howard, 2005, Spherical Boulders in North-Central Arkansas PDF version, 2.8 MB Arkansas Geological Commission Miscellaneous Publication n. 22, pp. 1-23.
- Heinrich, P. V. , 2007, The Giant Concretions of Rock City Kansas PDF version, 836 KB BackBender's Gazette. vol. 38, no. 8, pp. 6-12.
- Hokianga Tourism Association, nd, Koutu boulders Really nice pictures of cannonball concretions.
- Irna, 2007a, Stone balls : in France too!
- Irna, 2007b, Stone balls in Slovakia, Czech Republic and Poland
- Katz, B. , 1998, Concretions Digital West Media, Inc.
- McCollum, A. , nd, Sand Concretions from Imperial Valley, a collection of articles maintained by an American artist.
- Mozley, P. S. , Concretions, bombs, and groundwater, on-line version of an overview paper originally published by the New Mexico Bureau of Geology and Mineral Resources.
- United States Geological Survey, nd, cannonball concretion
- University of Utah, 2004, Earth Has 'Blueberries' Like Mars 'Moqui Marbles' Formed in Groundwater in Utah's National Parks press release about iron oxide and Martian concretions
Dictionary
concretion
-noun
- The process of aggregating or coalescing into a mass.
- A solid, hard mass formed by a process of aggregation or coalescence.
- (geology) A rounded mass of a mineral, sometimes found in sedimentary rock or on the ocean floor.
- The action of making something concrete or the result of such an action.
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