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Travertines Travertines occur as accumulations of Calcium Concretions essay produced from flowing water, often, hot springs, they are also formed from incrustation.
When chemical and biological processes, act together, they are responsible for the precipitation of freshwater calcium carbonate as travertines. Travertines often start by nucleating on top plants and covering them, or filling cavities in preexisting karst systems.
The controls of travertines can very extremely from tectonic to Concretions essay. Formation occurs in two basic fashions, invasive, via introduction of meteoric CO2, and evasive, via hydrothermal fluids rich in CO2 degassing.
Depending on the environment of deposition and the controls there are differing fabrics and micro textures as a result of the organisms that can thrive in those environments. Introduction Travetine deposits are accumulations of limestone formed in multiple freshwater environments.
They form primarily by the incrustation of other objects or organisms by biochemical precipitation. Travertines can encrust upper and lower plants, depending on how the water flows over the organism, it is more common for them to encrust algae,and mosses.
In somecases due to the shape and characteristics they posses they can be considered to be stromatalites. Travertine deposits have also been called tufa, calcareous tufa, plant-tufa, carbonate concretions, petrified moss, vaucheria tufa, chironomid tufa, spring-sinter, calcic-sinter, sinter crust, and many more names.
Some researchers suggest that the term sinter should be restricted to deposits of an abiotic formation that are typically more dense and compact than tufa; most sinter-crust includes flowstones and other types of speleothems underground karst features.
The definition of a travertine can be difficult to specify. Many of the current definitions neglect to mention temperature, or process of deposition; Concretions essay most comprehensive definition comes from Pentecost In order for precipitation of calcium carbonate to occur it is necessary for the level of CO2 in water to go down Ramon, Because of the way they precipitate travertines hold similat characteristics to that of traditional carbonates, to physio-chemical precipitation of carbonate; in streams, rivers, or flow channels, they are usually shaped by these natural rimstone dams and rimstone pools.
The dams are mainly formed by incrustation of vegetation the flowing water encounters, and also by interruption of the flowforming pools.
In these pools detritic sedimentation processes coexist with incrustation processes, sometimes choking out the frormation of carbonate or forcing the formation to occur further downstream over a larger area Ramon, Geochemistry Only a couple chemical processes are responsible for most travertine formation worlwide.
Almost all travertines form from the degassing of metogene carbon dioxide-rich groundwaters containing calcium. Groundwater that is capable of depositing travertine is produced when carbonic acid dissolves the carbonate rocks to form a solution containing calcium and bicarbonate ions.
Carbon dioxide is lost from the solution when it contacts the atmosphere, where the CO2 concentration is lower than that in equilibrium with the dissolving solution. The evasion of carbon dioxide occurs to the epigean atmosphere, additional CO2 loss is forced through photosynthesis of aquatic plants and evaporation Pentecost, These carbonates do not form through as a transfer of carbon dioxide to atmosphere and are not strictly travertines either Pentecost, As a result of the combination of the geochemisty induced by physiographic regions that the travertines formed in, they can be defined as meteogene or thermogene deposits.
Thermogene Travertines Soil and atmospheric carbon dioxide may be regarded as meteoric in origin, since the terrestrial vegetation and associated soil contains carbon obtained from the atmosphere. They form typically in cold-water springs in regions underlain by carbonates. Occasionally, such waters circulate deep beneath the ground where they become heated and rise as hot springs, but contain only the meteoric carrier.
Invasive meteogenes include those formed through the reaction of atmospheric CO2 with groundwater as described in Eq. The soil atmosphere is the largest contributor of carbonic acid causing limestone dissolution and the CO2 enrichment of groundwaters, a large portion is dissolved by percolating rainwater.
Meteogene travertines are divided into two categories; the evasive meteogenes where carbon dioxide evasion leads to travertine deposition, and invasive meteogenes where the reverse process leads to deposition. Thermogene Travertines usually contain some meteoric carrier, but most of the carbon dioxide originates from thermal process within and below the crust Branner, Thermally generated carbon dioxide dissolves in groundwater, often under considerable pressure and the resulting high concentrations of CO2 are capable of dissolving large volumes of rock, the solutions rising as hot, bubbling springs, forming a hydrothermal circuit.
Typical dissolved inorganic carbon DIC and Ca levels respectively, are two to ten times higher than most meteogene sources Pentecost, Rates of degassing and precipitation are correspondingly higher, providing distinctive fabrics and the travertine stable carbon isotope composition is generally heavier than meteogene waters.
Thermogene deposits have a more localized distribution than meteogenes, they are often associated with regions that have a recent volcanic or tectonic history. It is important to note that thermogene source waters are not necessarily hot, although this is frequently the case, the term applying to the source, rather than the exit temperature of the water.
Fabrics There are a multitude of fabrics related to the different organisms involved in the processes of travertine formation.The free Geology research paper (Concretions essay) presented on this page should not be viewed as a sample of our on-line writing service.
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There are a number of things that any good conclusion should do: Wrap up your essay without leaving anything out. Inform the reader that you have achieved the purpose of the essay. See her essay ‘Concretions’, in Hans Ar, View all notes Albert Elsen's remarks were also typical in this respect.
He proposed that we regard Arp as a modeller, on the grounds that ‘his forms are expansive and his beings pulsate rather than hold their breath’.
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Essay UK is a trading name of Student Academic Services Limited, a company registered in England . Concretions are the most varied-shaped rocks of the sedimentary world. The way concretions come to be is the mineral matter concentrates around the nucleus of a host rock.
The nucleus is often organic such as a tooth or leaf or shell or fossil. An Essay on the Diseases of the Bile, More Particularly Its Calculous Concretions, Called Gall-Stones (Classic Reprint) [William White] on kaja-net.com *FREE* shipping on qualifying offers. Excerpt from An Essay on the Diseases of the Bile, More Particularly Its Calculous Concretions, Called Gall Author: William White.