Editing Hadean (section)

==Rock dating==
{{further|Oldest dated rocks}}

Prior to the 1980s and the discovery of [[Oldest dated rocks|Hadean lithic fragments]], scientific narratives of the early Earth explanations were almost entirely in the hands of [[Geodynamics|geodynamic]] modelers.<ref>{{cite book |last1=Harrison |first1=T. Mark |title=Hadean earth |date=2020 |publisher=Springer |location=Cham |isbn=978-3030466862 |page=4}}</ref>

[[File:Jack Hills detrital zircons BSE micrographs.jpg|thumb|left|Backscatter electron micrograph of detrital zircons from the Hadean (4.404 ± 0.008 Ga) [[metasediment]]s of the [[Jack Hills]], [[Narryer Gneiss terrane]], [[Western Australia]]]]

In the last decades of the 20th century, geologists identified a few Hadean rocks from western [[Greenland]], northwestern [[Canada]], and [[Western Australia]]. In 2015, traces of carbon minerals interpreted as "remains of [[Biotic material|biotic life]]" were found in 4.1-billion-year-old rocks in Western Australia.<ref>{{cite news |agency=[[Associated Press]] |last=Borenstein |first=Seth |date=19 October 2015 |title=Hints of life on what was thought to be desolate early Earth |work=[[Excite (web portal)|Excite]] |publisher=[[Mindspark Interactive Network]] |location=Yonkers, NY |url=http://apnews.excite.com/article/20151019/us-sci--earliest_life-a400435d0d.html |access-date=2015-10-20}}</ref><ref>{{cite journal |last1=Bell |first1=Elizabeth A. |last2=Boehnike |first2=Patrick |last3=Harrison |first3=T. Mark |last4=Mao |first4=Wendy L. |display-authors=3 |date=19 October 2015 |title=Potentially biogenic carbon preserved in a 4.1 billion-year-old zircon |journal=Proc. Natl. Acad. Sci. U.S.A. |issn=1091-6490 |publisher=[[National Academy of Sciences]] |location=Washington, D.C. |doi=10.1073/pnas.1517557112 |doi-access=free |pmid=26483481 |pmc=4664351 |bibcode=2015PNAS..11214518B |volume=112 |issue=47 |pages=14518–21}}</ref>

The oldest dated [[zircon]] crystals, enclosed in a [[Metamorphism|metamorphosed]] [[sandstone]] [[Conglomerate (geology)|conglomerate]] in the [[Jack Hills]] of the [[Narryer Gneiss terrane]] of Western Australia, date to 4.404 ± 0.008 [[Giga-annum|Ga]].<ref name=Wilde2001>{{cite journal |last1=Wilde |first1=Simon A. |last2=Valley |first2=John W. |last3=Peck |first3=William H. |last4=Graham |first4=Colin M. |date=2001 |title=Evidence from detrital zircons for the existence of continental crust and oceans on the Earth 4.4 Gyr ago |journal=Nature |pmid=11196637 |bibcode=2001Natur.409..175W |s2cid=4319774 |doi=10.1038/35051550 |volume=409 |issue=6817 |pages=175–178}}</ref> This zircon is a slight outlier, with the oldest consistently dated zircon falling closer to 4.35 Ga<ref name=Wilde2001/>—around 200 million years after the hypothesized time of [[History of Earth#Origin of life|Earth's formation]].

In many other areas, [[xenocryst]] (or relict) [[Hadean zircon]]s enclosed in older rocks indicate that younger rocks have formed on older [[terrane]]s and have incorporated some of the older material. One example occurs in the [[Guiana Shield|Guiana shield]] from the Iwokrama Formation of southern Guyana where zircon cores have been dated at 4.22 Ga.<ref>{{cite journal |last1=Nadeau |first1=Serge |last2=Chen |first2=Wei |last3=Reece |first3=Jimmy |last4=Lachhman |first4=Deokumar |last5=Ault |first5=Randy |last6=Faraco |first6=Maria |last7=Fraga |first7=Leda |last8=Reis |first8=Nelson |last9=Betiollo |first9=Leandro |date=2013-12-01 |title=Guyana: the Lost Hadean crust of South America? |journal=Brazilian Journal of Geology |doi=10.5327/Z2317-48892013000400002 |doi-access=free |volume=43 |issue=4 |pages=601–606|bibcode=2013BrJG...43..601N }}</ref>