Rubuce-rubucen bayyanar ƙasa

Ranar bayyanar farfajiyar tarin dabarun geochronological ne don kimanta tsawon lokacin da aka 6" href="./Exposure_(geology)" "Exposure (geology)">fallasa dutse a ko kusa da farfajilar Duniya. Ana amfani da kwanan wata na bayyanar ƙasa don kwanan wata ci gaban glacial da koma baya, tarihin rushewa, kwararar dutse, tasirin meteorite, slides na dutse, ɓarkewar kuskure, ci gaban kogo, da sauran abubuwan da suka faru na ƙasa. Yana da amfani sosai ga duwatsu waɗanda aka fallasa tsakanin shekaru 103 zuwa 106.

## Rubuce-rubucen radionuclide na sararin samaniya
Mafi yawan waɗannan dabarun soyayya shine soyayya ta radionuclide. Duniya tana ci gaba da bombarded tare da primary cosmic rays, high makamashi caji barbashi - mafi yawa protons da alpha barbashi. Wadannan barbashi suna hulɗa tare da atoms a cikin iskar gas, suna samar da tarin barbashi na biyu wanda zai iya hulɗa da rage kuzari a cikin halayen da yawa yayin da suke wucewa cikin yanayi. Wannan cascade ya haɗa da ƙaramin ɓangaren hadrons, gami da neutrons. Lokacin da ɗaya daga cikin waɗannan barbashi ya buge atom zai iya cire ɗaya ko fiye da protons da / ko neutrons daga wannan atom, yana samar da wani abu daban ko kuma isotope daban na asalin asali. A cikin dutse da sauran kayan da ke da irin wannan yawa, yawancin Hasken sararin samaniya yana shawo kan mita na farko na kayan da aka fallasa a cikin halayen da ke samar da sabbin isotopes da ake kira cosmogenic nuclides. A farfajiyar Duniya yawancin waɗannan ƙwayoyin suna samuwa ne ta hanyar fashewa neutron. Yin amfani da wasu cosmogenic radionuclides, masana kimiyya na iya nuna tsawon lokacin da aka fallasa wani yanki, tsawon lokacin da an binne wani abu, ko kuma yadda wuri ko kwandon ruwa ke lalacewa. Ka'idar ta asali ita ce ana samar da waɗannan radionuclides a sanannen adadin, kuma suna lalacewa a sanannen canji. Dangane da haka, ta hanyar auna maida hankali ga waɗannan ƙwayoyin cosmogenic a cikin samfurin dutse, da lissafin ƙwayoyin hasken sararin samaniya da rabin rayuwar ƙwayoyin, yana yiwuwa a kiyasta tsawon lokacin da aka fallasa samfurin ga hasken sarkin sararin samaniya. Rashin hasken sararin samaniya a wani wuri na iya shafar abubuwa da yawa, gami da tsawo, latitude na geomagnetic, bambancin ƙarfin filin magnetic na Duniya, iskar rana, da kariya ta yanayi saboda bambancin matsin iska. Dole ne a kiyasta yawan samar da nucleid don kwanan wata samfurin dutse. Wadannan ƙididdigar yawanci ana kimanta su ta hanyar kwatanta maida hankali ga ƙwayoyin da aka samar a cikin samfurori waɗanda aka ƙayyade shekarunsu ta wasu hanyoyi, kamar su kwanan wata na radiocarbon, thermoluminescence, ko luminescence mai motsawa.

Yawan dangi 2" href="./Natural_abundance" id="mwMw" rel="mw:WikiLink" title="Natural abundance">da yawa na halitta na cosmogenic nuclides a cikin samfurin dutse yawanci ana auna shi ta hanyar hanzari mass spectrometry. Cosmogenic nuclides irin su ana samar da su ta hanyar sarƙoƙi na halayen spallation. Yawan samarwa don wani nau'i shine aikin latitude na geomagnetic, adadin sararin samaniya wanda za'a iya gani daga ma'anar da aka samo, tsawo, zurfin samfurin, da kuma yawan kayan da aka saka samfurin. Ana ba da ƙimar lalacewa ta hanyar ƙwayoyin lalacewa na nuclides. Wadannan daidaitattun za a iya haɗawa don ba da jimlar maida hankali ga cosmogenic radionuclides a cikin samfurin a matsayin aikin shekaru. Abubuwa biyu da aka fi auna su akai-akai sune [./Beryllium-&#x3C;sup&#x20;id= 10" id="mwLw" rel="mw:WikiLink" title="Beryllium-10">beryllium-10] da [./Aluminum-&#x3C;sup&#x20;id= 26" id="mwMA" rel="mw:WikiLink" title="Aluminum-26">aluminum-26]. Wadannan nuclides suna da amfani sosai ga masu ilimin ƙasa saboda ana samar da su lokacin da hasken sararin samaniya ya buge oxygen-16 da silicon-28, bi da bi. Iyaye isotopes sune mafi yawan waɗannan abubuwa, kuma sun zama ruwan dare a cikin kayan ɓawon burodi, yayin da ƙwayoyin 'yar rediyo ba a yawan samar da su ta wasu matakai. Kamar yadda Iskar oxygen-16 ta zama ruwan dare a cikin yanayi, dole ne a yi la'akari da gudummawar da aka ba da ita ga beryllium-10 daga kayan da aka ajiye maimakon ƙirƙirar *a wurin*. 10Be da 26Al ana samar da su ne lokacin da wani ɓangare na lu'ulu'u na Quartz (SiO2) ya bombarded da wani spallation samfurin: oxygen na quartz ya canza zuwa 10Be kuma silicon ya canza zuwa 26Al. Kowane ɗayan waɗannan ƙwayoyin suna samar da su a wani nau'i daban. Dukansu za a iya amfani da su daban-daban don kwanan wata yadda aka fallasa kayan a farfajiya. Saboda akwai radionuclides guda biyu da ke lalacewa, ana iya amfani da rabo na maida hankali ga waɗannan nuclides guda biyu ba tare da wani ilmi ba don tantance shekarun da aka binne samfurin bayan zurfin samarwa (yawanci mita 2-10).

Ana kuma auna ƙwayoyin Chlorine-36 zuwa kwanan wata dutsen ƙasa. Wannan isotope na iya samarwa ta hanyar hasken sararin samaniya na calcium ko potassium.

## Manazarta

* Geomorphology and in situ cosmogenic isotopes. Cerling, T.E. and Craig, H. Annual Review of Earth and Planetary Sciences, 22, 273-317, 1994.
* Terrestrial in situ cosmogenic nuclides: theory and application. Gosse, J.C. and Phillips, F.M. Quaternary Science Reviews, 20, 1475–1560, 2001. https://web.archive.org/web/20170905191044/https://pdfs.semanticscholar.org/5071/2bf05fcf4d7092623ac93cd05ff38d971d2a.pdf
* A complete and easily accessible means of calculating surface exposure ages or erosion rates from 10Be and 26Al measurements. Balco, Greg; Stone, John O.j Lifton, Nathaniel A.; Dunaic, Tibor J.; Quaternary Geochronology Volume 3, Issue 3, August 2008, Pages 174-195.https://www.researchgate.net/profile/Nathaniel_Lifton/publication/228372219_A_complete_and_easily_accessible_means_of_calculating_surface_exposure_ages_or_erosion_rates_from_10Be_and_26Al_measurements/links/00b7d5298c4eb84e86000000.pdf
* Geological calibration of spallation production rates in the CRONUS-Earth project.  Borchers, Brian; Marrero, Shasta; Balco, Greg; Caffee, Marc; Goehring, Brent; Lifton, Nathaniel; Nishiizumi, Kunihiko; Phillips, Fred; Schaefer, Joerg; Stone, John. Quaternary Geochronology Volume 31, February 2016, Pages 188–198.