Array ( [0] => {{Short description|Science of determining the age of rocks, sediments and fossils}} [1] => [[Image:Geological time spiral.png|thumb|right|300px|An artistic depiction of the major events in the history of Earth]] [2] => [3] => '''Geochronology''' is the [[science]] of [[Chronological dating|determining the age]] of [[rock (geology)|rocks]], [[fossil]]s, and [[sediment]]s using signatures inherent in the rocks themselves. Absolute geochronology can be accomplished through [[radioactive isotopes]], whereas relative geochronology is provided by tools such as [[paleomagnetism]] and [[stable isotope ratio]]s. By combining multiple geochronological (and [[biostratigraphic]]) indicators the precision of the recovered age can be improved. [4] => [5] => Geochronology is different in application from biostratigraphy, which is the science of assigning sedimentary rocks to a known geological period via describing, cataloging and comparing fossil floral and faunal assemblages. Biostratigraphy does not ''directly'' provide an absolute age determination of a rock, but merely places it within an ''interval'' of time at which that fossil assemblage is known to have coexisted. Both disciplines work together hand in hand, however, to the point where they share the same system of naming [[strata]] (rock layers) and the time spans utilized to classify sublayers within a stratum. [6] => [7] => The science of geochronology is the prime tool used in the discipline of [[chronostratigraphy]], which attempts to derive absolute age dates for all fossil assemblages and determine the geologic [[history of the Earth]] and [[List of Solar System objects by size|extraterrestrial bodies]]. [8] => [9] => == Dating methods == [10] => {{Geology to Paleobiology}} [11] => [12] => === Radiometric dating === [13] => {{main|Radiometric dating}} [14] => By measuring the amount of [[radioactive decay]] of a [[radioactive isotope]] with a known [[half-life]], geologists can establish the absolute age of the parent material. A number of radioactive isotopes are used for this purpose, and depending on the rate of decay, are used for dating different geological periods. More slowly decaying isotopes are useful for longer periods of time, but less accurate in absolute years. With the exception of the [[Radiocarbon dating|radiocarbon method]], most of these techniques are actually based on measuring an increase in the abundance of a [[radiogenic]] isotope, which is the decay-product of the radioactive parent isotope.Dickin, A. P. 1995. ''Radiogenic Isotope Geology''. Cambridge, Cambridge University Press. {{ISBN|0-521-59891-5}}Faure, G. 1986. ''Principles of isotope geology''. Cambridge, Cambridge University Press. {{ISBN|0-471-86412-9}}Faure, G., and Mensing, D. 2005. "Isotopes - Principles and applications". 3rd Edition. J. Wiley & Sons. {{ISBN|0-471-38437-2}} Two or more radiometric methods can be used in concert to achieve more robust results.{{cite journal | last1 = Dalrymple | first1 = G. B. | last2 = Grove | first2 = M. | last3 = Lovera | first3 = O. M. | last4 = Harrison | first4 = T. M. | last5 = Hulen | first5 = J. B. | last6 = Lanphere | first6 = M. A. | year = 1999 | title = Age and thermal history of the Geysers plutonic complex (felsite unit), Geysers geothermal field, California: a 40Ar/39Ar and U–Pb study | journal = Earth and Planetary Science Letters | volume = 173 | issue = 3| pages = 285–298 | doi = 10.1016/S0012-821X(99)00223-X | bibcode = 1999E&PSL.173..285D }} Most radiometric methods are suitable for geological time only, but some such as the radiocarbon method and the 40Ar/39Ar dating method can be extended into the time of early human life{{cite journal | last1 = Ludwig | first1 = K. R. | last2 = Renne | first2 = P. R. | year = 2000 | title = Geochronology on the Paleoanthropological Time Scale | url = http://www3.interscience.wiley.com/journal/72000094/abstract?CRETRY=1&SRETRY=0 | archive-url = https://archive.today/20130105085933/http://www3.interscience.wiley.com/journal/72000094/abstract?CRETRY=1&SRETRY=0 | url-status = dead | archive-date = 2013-01-05 | journal = Evolutionary Anthropology | volume = 9 | issue = 2| pages = 101–110 | doi = 10.1002/(sici)1520-6505(2000)9:2<101::aid-evan4>3.0.co;2-w | s2cid = 83948790 }} and into recorded history.Renne, P. R., Sharp, W. D., Deino. A. L., Orsi, G., and Civetta, L. 1997. ''Science'', '''277''', 1279-1280 {{cite web |url=http://www.pereplet.ru/gorm/dating/vesuvius.pdf |title=40Ar/39Ar dating into the historical realm: Calibration against Pliny the Younger |access-date=2008-10-25 |url-status=dead |archive-url=https://web.archive.org/web/20081030142813/http://www.pereplet.ru/gorm/dating/vesuvius.pdf |archive-date=2008-10-30 }} [15] => [16] => Some of the commonly used techniques are: [17] => * [[Radiocarbon dating]]. This technique measures the decay of [[carbon-14]] in organic material and can be best applied to samples younger than about 60,000 years.{{cite journal |last=Plastino |first=W. |author2=Kaihola, L. |author3=Bartolomei, P. |author4=Bella, F. |year=2001 |title=Cosmic Background Reduction In The Radiocarbon Measurement By Scintillation Spectrometry At The Underground Laboratory Of Gran Sasso |journal=Radiocarbon |volume=43 |issue=2A |pages=157–161 |doi=10.1017/S0033822200037954 |doi-access=free }}{{Cite journal |last1=Hajdas |first1=Irka |last2=Ascough |first2=Philippa |last3=Garnett |first3=Mark H. |last4=Fallon |first4=Stewart J. |last5=Pearson |first5=Charlotte L. |last6=Quarta |first6=Gianluca |last7=Spalding |first7=Kirsty L. |last8=Yamaguchi |first8=Haruka |last9=Yoneda |first9=Minoru |date=2021-09-09 |title=Radiocarbon dating |journal=Nature Reviews Methods Primers |language=en |volume=1 |issue=1 |pages=1–26 |doi=10.1038/s43586-021-00058-7 |issn=2662-8449|doi-access=free }} [18] => * [[Uranium–lead dating]]. This technique measures the ratio of two lead [[isotope]]s (lead-206 and lead-207) to the amount of uranium in a mineral or rock. Often applied to the trace mineral [[zircon]] in [[igneous rock]]s, this method is one of the two most commonly used (along with [[argon–argon dating]]) for geologic dating. [[Monazite geochronology]] is another example of U–Pb dating, employed for dating metamorphism in particular. Uranium–lead dating is applied to samples older than about 1 million years. [19] => * [[Uranium–thorium dating]]. This technique is used to date [[speleothem]]s, [[coral]]s, [[carbonate]]s, and fossil [[bone]]s. Its range is from a few years to about 700,000 years. [20] => * [[Potassium–argon dating]] and [[argon–argon dating]]. These techniques date [[Metamorphic rock|metamorphic]], [[igneous rock|igneous]] and [[volcanic rock|volcanic]] rocks. They are also used to date [[volcanic ash]] layers within or overlying [[paleoanthropology|paleoanthropologic]] sites. The younger limit of the argon–argon method is a few thousand years. [21] => * [[Electron spin resonance]] (ESR) dating [22] => [23] => === Fission-track dating === [24] => {{main|Fission track dating}} [25] => [26] => === Cosmogenic nuclide geochronology === [27] => {{Main|Cosmogenic radionuclide dating}} [28] => A series of related techniques for determining the age at which a geomorphic surface was created ([[Cosmogenic dating|exposure dating]]), or at which formerly [[Surficial deposit|surficial materials]] were buried (burial dating).{{Cite journal |last1=Schaefer |first1=Joerg M. |last2=Codilean |first2=Alexandru T. |last3=Willenbring |first3=Jane K. |last4=Lu |first4=Zheng-Tian |last5=Keisling |first5=Benjamin |last6=Fülöp |first6=Réka-H. |last7=Val |first7=Pedro |date=2022-03-10 |title=Cosmogenic nuclide techniques |url=https://www.nature.com/articles/s43586-022-00096-9 |journal=Nature Reviews Methods Primers |language=en |volume=2 |issue=1 |pages=1–22 |doi=10.1038/s43586-022-00096-9 |s2cid=247396585 |issn=2662-8449}} Exposure dating uses the concentration of exotic nuclides (e.g. 10Be, 26Al, 36Cl) produced by cosmic rays interacting with Earth materials as a proxy for the age at which a surface, such as an alluvial fan, was created. Burial dating uses the differential radioactive decay of 2 cosmogenic elements as a proxy for the age at which a sediment was screened by burial from further cosmic rays exposure. [29] => [30] => === Luminescence dating === [31] => Luminescence dating techniques observe 'light' emitted from materials such as quartz, diamond, feldspar, and calcite. Many types of luminescence techniques are utilized in geology, including [[optically stimulated luminescence]] (OSL), [[cathodoluminescence]] (CL), and [[thermoluminescence]] (TL).{{Cite journal |last1=Murray |first1=Andrew |last2=Arnold |first2=Lee J. |last3=Buylaert |first3=Jan-Pieter |last4=Guérin |first4=Guillaume |last5=Qin |first5=Jintang |last6=Singhvi |first6=Ashok K. |last7=Smedley |first7=Rachel |last8=Thomsen |first8=Kristina J. |date=2021-10-28 |title=Optically stimulated luminescence dating using quartz |url=https://www.nature.com/articles/s43586-021-00068-5 |journal=Nature Reviews Methods Primers |language=en |volume=1 |issue=1 |pages=1–31 |doi=10.1038/s43586-021-00068-5 |s2cid=240186965 |issn=2662-8449}} Thermoluminescence and optically stimulated luminescence are used in archaeology to date 'fired' objects such as pottery or cooking stones and can be used to observe sand migration. [32] => [33] => === Incremental dating === [34] => {{Main|Incremental dating}} [35] => [[Incremental dating]] techniques allow the construction of year-by-year annual chronologies, which can be fixed (''i.e.'' linked to the present day and thus [[calendar]] or [[sidereal time]]) or floating. [36] => * [[Dendrochronology]] [37] => * [[Ice core]]s [38] => * [[Lichenometry]] [39] => * [[Varve]]s [40] => [41] => === Paleomagnetic dating === [42] => A sequence of [[paleomagnetic pole]]s (usually called virtual geomagnetic poles), which are already well defined in age, constitutes an [[apparent polar wander]] path (APWP). Such a path is constructed for a large continental block. APWPs for different continents can be used as a reference for newly obtained poles for the rocks with unknown age. For paleomagnetic dating, it is suggested to use the APWP in order to date a pole obtained from rocks or sediments of unknown age by linking the paleopole to the nearest point on the APWP. Two methods of paleomagnetic dating have been suggested: (1) the angular method and (2) the rotation method.Hnatyshin, D., and Kravchinsky, V.A., 2014. Paleomagnetic dating: Methods, MATLAB software, example. Tectonophysics, doi: 10.1016/j.tecto.2014.05.013 [https://dx.doi.org/10.1016/j.tecto.2014.05.013] The first method is used for paleomagnetic dating of rocks inside of the same continental block. The second method is used for the folded areas where tectonic rotations are possible. [43] => [44] => === Magnetostratigraphy === [45] => {{Main|Magnetostratigraphy}} [46] => [[Magnetostratigraphy]] determines age from the pattern of magnetic polarity zones in a series of bedded sedimentary and/or volcanic rocks by comparison to the magnetic polarity timescale. The polarity timescale has been previously determined by dating of seafloor magnetic anomalies, radiometrically dating volcanic rocks within magnetostratigraphic sections, and astronomically dating magnetostratigraphic sections. [47] => [48] => === Chemostratigraphy === [49] => Global trends in isotope compositions, particularly carbon-13 and strontium isotopes, can be used to correlate strata.{{cite journal|title=The falling amplitude of carbon isotopic oscillations through the Lower to Middle Cambrian: northern Siberia data|first1=M D|last1=Brasier|first2=S S|last2=Sukhov|date=1 April 1998|journal=Canadian Journal of Earth Sciences|volume=35|issue=4|pages=353–373|doi=10.1139/e97-122|bibcode=1998CaJES..35..353B}} [50] => [51] => === Correlation of marker horizons === [52] => [[File:Icelandic tephra.JPG|250px|thumb|right|Tephra horizons in south-central [[Iceland]]. The thick and light-to-dark coloured layer at the height of the [[volcanologist]]'s hands is a marker horizon of [[rhyolitic]]-to-[[basalt]]ic [[tephra]] from [[Hekla]].]] [53] => [[Marker horizon]]s are stratigraphic units of the same age and of such distinctive composition and appearance that, despite their presence in different geographic sites, there is certainty about their age-equivalence. Fossil faunal and floral [[fossil|assemblage]]s, both marine and terrestrial, make for distinctive marker horizons.{{cite journal | last1 = Demidov | first1 = I.N. | year = 2006 | title = Identification of marker horizon in bottom sediments of the Onega Periglacial Lake | journal = Doklady Earth Sciences | volume = 407 | issue = 1| pages = 213–216 | doi = 10.1134/S1028334X06020127 | bibcode = 2006DokES.407..213D | s2cid = 140634223 }} [[Tephrochronology]] is a method for geochemical correlation of unknown volcanic ash (tephra) to geochemically fingerprinted, dated [[tephra]]. Tephra is also often used as a dating tool in archaeology, since the dates of some eruptions are well-established. [54] => [55] => == Geological hierarchy of chronological periodization == [56] => Geochronology, from largest to smallest: [57] => # [[Supereon]] [58] => # [[Eon (geology)|Eon]] [59] => # [[Era (geology)|Era]] [60] => # [[Period (geology)|Period]] [61] => # [[Epoch (geology)|Epoch]] [62] => # [[Age (geology)|Age]] [63] => # [[Polarity chron|Chron]] [64] => [65] => == Differences from chronostratigraphy == [66] => It is important not to confuse geochronologic and chronostratigraphic units.David Weishampel: ''The Evolution and Extinction of the Dinosaurs'', 1996, Cambridge Press, {{ISBN|0-521-44496-9}} Geochronological units are periods of time, thus it is correct to say that ''[[Tyrannosaurus]] rex'' lived during the Late [[Cretaceous]] Epoch.Julia Jackson: ''Glossary of Geology'', 1987, American Geological Institute, {{ISBN|0-922152-34-9}} Chronostratigraphic units are geological material, so it is also correct to say that fossils of the genus ''Tyrannosaurus'' have been found in the Upper Cretaceous Series.{{cite journal | last1 = Smith | first1 = J.B. | last2 = Lamanna | first2 = M.C. | last3 = Lacovara | first3 = K.J. | last4 = Dodson | first4 = Poole | last5 = Jnr | first5 = P. | last6 = Giegengack | first6 = R. | year = 2001 | title = A Giant Sauropod Dinosaur from an Upper Cretaceous Mangrove Deposit in Egypt | journal = Science | volume = 292 | issue = 5522| pages = 1704–1707 | doi = 10.1126/science.1060561 | pmid = 11387472 | bibcode = 2001Sci...292.1704S | s2cid = 33454060 | url = http://doc.rero.ch/record/14792/files/PAL_E1924.pdf }} In the same way, it is entirely possible to go and visit an Upper Cretaceous Series deposit – such as the [[Hell Creek]] deposit where the ''Tyrannosaurus'' fossils were found – but it is naturally impossible to visit the Late Cretaceous Epoch as that is a period of time. [67] => [68] => == See also == [69] => * [[Astronomical chronology]] [70] => ** [[Age of Earth]] [71] => ** [[Age of the universe]] [72] => * [[Chronological dating]], archaeological chronology [73] => ** [[Absolute dating]] [74] => ** [[Relative dating]] [75] => ** [[Phase (archaeology)]] [76] => ** [[Archaeological association]] [77] => * Geochronology [78] => ** [[Closure temperature]] [79] => ** [[Geologic time scale]] [80] => ** [[Geological history of Earth]] [81] => ** [[Thermochronology]] [82] => ** [[List of geochronologic names]] [83] => * General [84] => ** [[Consilience]], evidence from independent, unrelated sources can "converge" on strong conclusions [85] => [86] => == References == [87] => {{Reflist}} [88] => [89] => == Further reading == [90] => * Smart, P.L., and Frances, P.D. (1991), ''Quaternary dating methods - a user's guide''. Quaternary Research Association Technical Guide No.4 {{ISBN|0-907780-08-3}} [91] => * Lowe, J.J., and Walker, M.J.C. (1997), ''Reconstructing Quaternary Environments'' (2nd edition). Longman publishing {{ISBN|0-582-10166-2}} [92] => * Mattinson, J. M. (2013), ''Revolution and evolution: 100 years of U-Pb geochronology''. Elements 9, 53–57. [93] => * ''Geochronology bibliography'' [http://www.talkorigins.org/origins/biblio/geochronology.html Talk:Origins Archive] [94] => [95] => ==External links== [96] => * [https://portal.ga.gov.au/persona/geochronology Geochronology and Isotopes Data Portal ] [97] => * [http://stratigraphy.org/ International Commission on Stratigraphy ] [98] => * [http://data.bgs.ac.uk/home.html BGS Open Data ] [http://trimc-nlp.blogspot.com/2013/09/ontology-models-for-geochronology-and.html Geochronological Ontologies] [99] => [100] => {{Geology}} [101] => {{Time Topics}} [102] => {{Chronology}} [103] => {{Authority control}} [104] => [105] => [[Category:Geochronology| ]] [106] => [[Category:Radiometric dating]] [] => )
good wiki

Geochronology

Geochronology is the science of determining the age of rocks, fossils, and sediments using signatures inherent in the rocks themselves. Absolute geochronology can be accomplished through radioactive isotopes, whereas relative geochronology is provided by tools such as paleomagnetism and stable isotope ratios.

More about us

About

Expert Team

Vivamus eget neque lacus. Pellentesque egauris ex.

Award winning agency

Lorem ipsum, dolor sit amet consectetur elitorceat .

10 Year Exp.

Pellen tesque eget, mauris lorem iupsum neque lacus.

You might be interested in

Calendar

A calendar is a system used to organize and measure time.

Carbon-14

Carbon-14 is a radioactive isotope of carbon that is commonly used to determine the age of ancient artifacts and archaeological remains.

Coral

Coral is a type of marine invertebrate that belongs to the phylum Cnidaria.

Dendrochronology

Dendrochronology (or tree-ring dating) is the scientific method of dating tree rings (also called growth rings) to the exact year they were formed in a tree.

Isotope

An isotope is a variant form of a chemical element that has the same number of protons but a different number of neutrons, giving it a different atomic mass.

Science

Science is a systematic and empirical approach to acquiring knowledge through observation, experimentation, and explanation of natural phenomena.