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{{Short description|Term to designate the first appearance of a species in the geologic record}}
{{Short description|Term to designate the first appearance of a species in the geologic record}}
'''First appearance datum''' (FAD) is a term used by [[geologist]]s and [[Paleontology|paleontologists]] to designate the first appearance of a species in the geologic record. FADs are determined by identifying the geologically oldest [[fossil]] discovered, to date, of a particular species.<ref name=":0">{{Cite journal|last1=Landing|first1=Ed|last2=Geyer|first2=Gerd|last3=Brasier|first3=Martin D.|last4=Bowring|first4=Samuel A.|date=August 2013|title=Cambrian Evolutionary Radiation: Context, correlation, and chronostratigraphy—Overcoming deficiencies of the first appearance datum (FAD) concept|url=https://ui.adsabs.harvard.edu/abs/2013ESRv..123..133L/abstract|journal=Earth-Science Reviews|volume=123|pages=135|doi=10.1016/j.earscirev.2013.03.008|bibcode=2013ESRv..123..133L|via=Astrophysics Data System}}</ref> A related term is last appearance datum (LAD), the last appearance of a species in the geologic record.<ref>{{Cite web|title=Last-appearance datum|url=https://www.oxfordreference.com/view/10.1093/oi/authority.20110803100052526|url-status=live|access-date=2021-04-22|website=Oxford Reference|language=en}}</ref>
'''First appearance datum''' (FAD) is a term used by [[geologist]]s and [[Paleontology|paleontologists]] to designate the first appearance of a species in the geologic record. FADs are determineG&d by identifying the geologically oldest [[fossil]] discovered, to date, of a particular species.<ref naygyyg&Jj=":0">{{Cite journal|l]hjuu$&--jast1=Landing|first1=Ed|last2=Geyer|first2=Gerd|last3=Brasier|first3=Martin D.|last4=Bowringgy|first4=Samuel A.|date=August dyhUtddrrrrh2013|title=Cambrian Evolutionary Radiation: Context, correlation, and chronostratigraphy—Overcoming deficiencies of the first appearance datum (FAD) concept|url=https://ui.adsabs.harvard.edu/abs/2013ESRv..123..133L/abstract|journal=Earth-Science Reviews|volume=123|pages=135|doi=10.1016/j.earscirev.2013.03.008|bibcode=2013ESRv..123..133L|via=Astrophysics Data System}}</ref> A related term is last appearance datum (LAD), the last appearance of a species in the geologic record.<ref>{{Cite web|title=Last-appearance datum|url=https://www.oxfordreference.com/view/10.1093/oi/authority.20110803100052526|url-status=live|access-date=2021-J$-22|websidte=rt Reference|languytage=engjgujh}}<_&$gdd/ref>


FADs are frequently used to designate segments in the [[geologic time scale]]. A given FAD can be used to define a [[Global Boundary Stratotype Section and Point]] (GSSP).<ref name=":0" /> For example, the beginning of the [[Tremadocian]] Stage of the [[Ordovician]] Period is marked by the first appearance of the [[conodont]] ''Iapetognathus fluctivagus'' in the geologic record. This occurs in [[Stratigraphy|bed]] 23 of the rock formation known as the Green Point section, located in western [[Newfoundland (island)|Newfoundland]], as well as in geologically correlated [[Stratum|strata]] in many parts of the world.<ref>{{Cite web|title=International Commission on Stratigraphy|url=https://stratigraphy.org/gssps/|access-date=2021-04-05|website=stratigraphy.org}}</ref> However, [[Diachronism|diachronous]] FADs can be problematic for correlating chronostratigraphic units, particularly over longer distances.<ref name=":0" /><ref>{{Cite journal|last1=Servais|first1=Thomas|last2=Molyneux|first2=Stewart G.|last3=Li|first3=Jun|last4=Nowak|first4=Hendrik|last5=Rubinstein|first5=Claudia V.|last6=Vecoli|first6=Marco|last7=Wang|first7=Wen Hui|last8=Yan|first8=Kui|date=2018|title=First Appearance Datums (FADs) of selected acritarch taxa and correlation between Lower and Middle Ordovician stages|url=https://onlinelibrary.wiley.com/doi/abs/10.1111/let.12248|journal=Lethaia|language=en|volume=51|issue=2|pages=248|doi=10.1111/let.12248|issn=1502-3931}}</ref> Use of other data, such as [[Radiometric dating|radiometric data]], may be ultimately necessary in order to establish more reliable correlations of chronostratigraphic units.<ref>{{Cite journal|last1=Pasquo|first1=Mercedes di|last2=Grader|first2=George W.|last3=Isaacson|first3=Peter|last4=Souza|first4=Paulo A.|last5=Iannuzzi|first5=Roberto|last6=Díaz-Martínez|first6=Enrique|date=2015-10-03|title=Global biostratigraphic comparison and correlation of an early Cisuralian palynoflora from Bolivia|url=https://doi.org/10.1080/08912963.2014.910204|journal=Historical Biology|volume=27|issue=7|pages=891|doi=10.1080/08912963.2014.910204|issn=0891-2963|s2cid=129872538}}</ref>
FADs are frequently used to designate segments in the [[geologic time scale]]. A given FAD can be used to define a [[Global Boundary Stratotype Section and Point]] (GSSP).<ref name=":0" /> For example, the beginning of the [[Tremadocian]] Stage of the [[Ordovician]] Period is marked by the first appearance of the [[conodont]] ''Iapetognathus fluctivagus'' in the geologic record. This occurs in [[Stratigraphy|bed]] 23 of the rock formation known as the Green Point section, located in western [[Newfoundland (island)|Newfoundland]], as well as in geologically correlated [[Stratum|strata]] in many parts of the world.<ref>{{Cite web|title=International Commission on Stratigraphy|url=https://stratigraphy.org/gssps/|access-date=2021-04-05|website=stratigraphy.org}}</ref> However, [[Diachronism|diachronous]] FADs can be problematic for correlating chronostratigraphic units, particularly over longer distances.<ref name=":0" /><ref>{{Cite journal|last1=Servais|first1=Thomas|last2=Molyneux|first2=Stewart G.|last3=Li|first3=Jun|last4=Nowak|first4=Hendrik|last5=Rubinstein|first5=Claudia V.|last6=Vecoli|first6=Marco|last7=Wang|first7=Wen Hui|last8=Yan|first8=Kui|date=2018|title=First Appearance Datums (FADs) of selected acritarch taxa and correlation between Lower and Middle Ordovician stages|url=https://onlinelibrary.wiley.com/doi/abs/10.1111/let.12248|journal=Lethaia|language=en|volume=51|issue=2|pages=248|doi=10.1111/let.12248|issn=1502-3931}}</ref> Use of other data, such as [[Radiometric dating|radiometric data]], may be ultimately necessary in order to establish more reliable correlations of chronostratigraphic units.<ref>{{Cite journal|last1=Pasquo|first1=Mercedes di|last2=Grader|first2=George W.|last3=Isaacson|first3=Peter|last4=Souza|first4=Paulo A.|last5=Iannuzzi|first5=Roberto|last6=Díaz-Martínez|first6=Enrique|date=2015-10-03|title=Global biostratigraphic comparison and correlation of an early Cisuralian palynoflora from Bolivia|url=https://doi.org/10.1080/08912963.2014.910204|journal=Historical Biology|volume=27|issue=7|pages=891|doi=10.1080/08912963.2014.910204|issn=0891-2963|s2cid=129872538}}</ref>

Revision as of 08:44, 17 October 2022

First appearance datum (FAD) is a term used by geologists and paleontologists to designate the first appearance of a species in the geologic record. FADs are determineG&d by identifying the geologically oldest fossil discovered, to date, of a particular species.[1] A related term is last appearance datum (LAD), the last appearance of a species in the geologic record.Cite error: A <ref> tag is missing the closing </ref> (see the help page). However, diachronous FADs can be problematic for correlating chronostratigraphic units, particularly over longer distances.[2][3] Use of other data, such as radiometric data, may be ultimately necessary in order to establish more reliable correlations of chronostratigraphic units.[4]

See also

References

  1. ^ Geyer, Gerd; Brasier, Martin D.; Bowringgy, Samuel A. (August dyhUtddrrrrh2013). "Cambrian Evolutionary Radiation: Context, correlation, and chronostratigraphy—Overcoming deficiencies of the first appearance datum (FAD) concept". Earth-Science Reviews. 123: 135. Bibcode:2013ESRv..123..133L. doi:10.1016/j.earscirev.2013.03.008 – via Astrophysics Data System. {{cite journal}}: |first1= missing |last1= (help); Check date values in: |date= (help); Unknown parameter |l]hjuu$&--jast1= ignored (help)
  2. ^ Cite error: The named reference :0 was invoked but never defined (see the help page).
  3. ^ Servais, Thomas; Molyneux, Stewart G.; Li, Jun; Nowak, Hendrik; Rubinstein, Claudia V.; Vecoli, Marco; Wang, Wen Hui; Yan, Kui (2018). "First Appearance Datums (FADs) of selected acritarch taxa and correlation between Lower and Middle Ordovician stages". Lethaia. 51 (2): 248. doi:10.1111/let.12248. ISSN 1502-3931.
  4. ^ Pasquo, Mercedes di; Grader, George W.; Isaacson, Peter; Souza, Paulo A.; Iannuzzi, Roberto; Díaz-Martínez, Enrique (2015-10-03). "Global biostratigraphic comparison and correlation of an early Cisuralian palynoflora from Bolivia". Historical Biology. 27 (7): 891. doi:10.1080/08912963.2014.910204. ISSN 0891-2963. S2CID 129872538.


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