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Before Present

January 19, 2024

"YBP" and "ybp" redirect here. For other uses, see YBP (disambiguation).

Before Present (BP) years, also known as "time before present" or "years before present (YBP)", is a time scale used mainly in archaeology, geology, and other scientific disciplines to specify when events occurred relative to the origin of practical radiocarbon dating in the 1950s. Because the "present" time changes, standard practice is to use 1 January 1950 as the commencement date (epoch) of the age scale. The abbreviation "BP" has been interpreted retrospectively as "Before Physics",[1] which refers to the time before nuclear weapons testing artificially altered the proportion of the carbon isotopes in the atmosphere, which scientists must now account for.[2][3]

In a convention that is not always observed, many sources restrict the use of BP dates to those produced with radiocarbon dating; the alternative notation RCYBP stands for the explicit "radio carbon years before present".

Usage edit

The BP scale is sometimes used for dates established by means other than radiocarbon dating, such as stratigraphy.[4][5] This usage differs from the recommendation by van der Plicht & Hogg,[6] followed by the Quaternary Science Reviews,[7][8] both of which requested that publications should use the unit "a" (for "annum", Latin for "year") and reserve the term "BP" for radiocarbon estimations.

Some archaeologists use the lowercase letters bp, bc and ad as terminology for uncalibrated dates for these eras.[9]

The Centre for Ice and Climate at the University of Copenhagen instead uses the unambiguous "b2k", for "years before 2000 CE", not necessarily, however, often in combination with the Greenland Ice Core Chronology 2005 (GICC05) time scale.[10]

Some authors who use the YBP dating format also use YAP (years after present) to denote years after 1950.[11]

SI prefixes edit

SI prefix multipliers may be used to express larger periods of time, e.g. ka BP (thousand years BP), Ma BP (million years BP) and many others.[12]

Radiocarbon dating edit

Radiocarbon dating was first used in 1949.[13][14] Beginning in 1954, metrologists established 1950 as the origin year for the BP scale for use with radiocarbon dating, using a 1950-based reference sample of oxalic acid. According to scientist A. Currie Lloyd:

The problem was tackled by the international radiocarbon community in the late 1950s, in cooperation with the U.S. National Bureau of Standards. A large quantity of contemporary oxalic acid dihydrate was prepared as NBS Standard Reference Material (SRM) 4990B. Its 14C concentration was about 5% above what was believed to be the natural level, so the standard for radiocarbon dating was defined as 0.95 times the 14C concentration of this material, adjusted to a 13C reference value of −19 per mil (PDB). This value is defined as "modern carbon" referenced to AD 1950. Radiocarbon measurements are compared to this modern carbon value, and expressed as "fraction of modern" (fM). "Radiocarbon ages" are calculated from fM using the exponential decay relation and the "Libby half-life" 5568 a. The ages are expressed in years before present (BP) where "present" is defined as AD 1950.[15]

The year 1950 was chosen because it was the standard astronomical epoch at that time.[citation needed] It also marked[2] the publication of the first radiocarbon dates in December 1949,[16] and 1950 also antedates large-scale atmospheric testing of nuclear weapons, which altered the global ratio of carbon-14 to carbon-12.[17]

Radiocarbon calibration edit

Main article: Radiocarbon dating § Calibration

Dates determined using radiocarbon dating come as two kinds: uncalibrated (also called Libby or raw) and calibrated (also called Cambridge) dates.[18] Uncalibrated radiocarbon dates should be clearly noted as such by "uncalibrated years BP", because they are not identical to calendar dates. This has to do with the fact that the level of atmospheric radiocarbon (carbon-14 or 14C) has not been strictly constant during the span of time that can be radiocarbon-dated. Uncalibrated radiocarbon ages can be converted to calendar dates by calibration curves based on comparison of raw radiocarbon dates of samples independently dated by other methods, such as dendrochronology (dating based on tree growth-rings) and stratigraphy (dating based on sediment layers in mud or sedimentary rock). Such calibrated dates are expressed as cal BP, where "cal" indicates "calibrated years", or "calendar years", before 1950.

Many scholarly and scientific journals require that published calibrated results be accompanied by the name (standard codes are used) of the laboratory concerned, and other information such as confidence levels, because of differences between the methods used by different laboratories and changes in calibrating methods.

Conversion edit

Conversion from Gregorian calendar years to Before Present years is by starting with the 1950-01-01 epoch of the Gregorian calendar and increasing the BP year count with each year into the past from that Gregorian date.

For example, 1000 BP corresponds to 950 CE, 1949 BP corresponds to 1 CE, 1950 BP corresponds to 1 BCE, 2000 BP corresponds to 51 BCE.

Example milestone years in the BP time scale
Gregorian year BP year Event
9701 BC 11650 BP End of the Pleistocene and beginning of the Holocene epoch[19]
4714 BC 6663 BP Epoch of the Julian day system: Julian day 0 starts at Greenwich noon on January 1, 4713 BC of the proleptic Julian calendar, which is November 24, 4714 BC in the proleptic Gregorian calendar[20]: 10 
2251 BC 4200 BP Beginning of the Meghalayan age, the current and latest of the three stages in the Holocene era.[21][22]
45 BC 1994 BP Introduction of the Julian calendar
1 BC 1950 BP Year zero at ISO 8601
AD 1 1949 BP Beginning of the Common Era and Anno Domini, from the estimate by Dionysius of the Incarnation of Jesus
1582 368 BP Introduction of the Gregorian calendar[20]: 47 
1950 – Epoch of the Before Present dating scheme[23]: 190 
2024 74 YAP Current year

See also edit

Citations edit

  1. ^ Flint, Richard Foster; Deevey, Edward S (1962). "Volume 4 – 1962". Radiocarbon. 4 (1): i.
  2. ^ a b Taylor RE (1985). "The beginnings of radiocarbon dating in American Antiquity: a historical perspective". American Antiquity. 50 (2): 309–325. doi:10.2307/280489. JSTOR 280489. S2CID 163900461.
  3. ^ Dincauze, Dena (2000). "Measuring time with isotopes and magnetism". Environmental Archaeology: Principles and Practice. Cambridge, England: Cambridge University Press. p. 110. ISBN 978-0-5213-1077-2.
  4. ^ . American Geophysical Union. 21 September 2007. Archived from the original on 2008-07-14. Retrieved 2009-01-09.
  5. ^ North American Commission on Stratigraphic Nomenclature (November 2005). . The American Association of Petroleum Geologists Bulletin. 89 (11): 1547–1591. doi:10.1306/07050504129. Archived from the original on 2014-02-02. Retrieved 2009-06-29.
  6. ^ van der Plicht, Johannes; Hogg, Alan (2006). "A note on reporting radiocarbon" (PDF). Quaternary Geochronology. 1 (4): 237–240. doi:10.1016/j.quageo.2006.07.001. S2CID 128628228.
  7. ^ "The use of time units in Quaternary Science Reviews". Quaternary Science Reviews. 26 (9–10): 1193. May 2007. Bibcode:2007QSRv...26.1193.. doi:10.1016/j.quascirev.2007.04.002.
  8. ^ Wolff, Eric W. (December 2007). "When is the "present"?". Quaternary Science Reviews. 26 (25–28): 3023–3024. Bibcode:2007QSRv...26.3023W. doi:10.1016/j.quascirev.2007.10.008. S2CID 131227900.
  9. ^ Edward J. Huth (25 November 1994). Scientific Style and Format: The CBE Manual for Authors, Editors, and Publishers. Cambridge University Press. pp. 495–. ISBN 978-0-521-47154-1. Retrieved 4 October 2012.
  10. ^ . Centre for Ice and Climate – University of Copenhagen. 3 September 2009. Archived from the original on 18 September 2018. Retrieved September 17, 2018.
  11. ^ Berger, André (1988). "Milankovitch Theory and Climate". Reviews of Geophysics. 26 (4): 624–657. doi:10.1029/RG026i004p00624. ISSN 8755-1209.
  12. ^ Martin Kölling (2015). "Numerous ways to say "thousand years" in a scientific paper". Universität Bremen: Marine Geochemistry - Laboratory Methods. Retrieved 2023-03-24.
  13. ^ Arnold, J.R.; Libby, W.F. (1949). "Age determinations by radiocarbon content: checks with samples of known age". Science. 110 (2869): 678–680. Bibcode:1949Sci...110..678A. doi:10.1126/science.110.2869.678. JSTOR 1677049. PMID 15407879.
  14. ^ Aitken (1990), pp. 60–61.
  15. ^ Currie, Lloyd A (March–April 2004). (PDF). Journal of Research of the National Institute of Standards and Technology. 109 (2): 185–217. doi:10.6028/jres.109.013. PMC 4853109. PMID 27366605. Archived from the original (PDF) on 2010-12-06. Retrieved 30 October 2019. "The Remarkable Metrological History of Radiocarbon Dating [II]" 2023-01-01 at the Wayback Machine at Google Books (accessed 30 October 2019).
  16. ^ Arnold JR, Libby WF (1949-03-04). "Age determinations by radiocarbon content: Checks with samples of known age". Science. 109 (2827): 227–228. Bibcode:1949Sci...109..227L. doi:10.1126/science.109.2827.227. PMID 17818054.
  17. ^ "Nuclear Bombs Made It Possible to Carbon Date Human Tissue". Smithsonian Magazine. 2013-02-19. Retrieved 2020-01-09.
  18. ^ Greene, Kevin (2002). Archaeology: An Introduction. Philadelphia: University of Pennsylvania Press. pp. 165–167. ISBN 0-8122-1828-0.
  19. ^ Walker, Mike; Jonsen, Sigfus; Rasmussen, Sune Olander; Popp, Trevor; Steffensen, Jørgen-Peder; Gibbard, Phil; Hoek, Wim; Lowe, John; Andrews, John; Björck, Svante; Cwynar, Les C.; Hughen, Konrad; Kershaw, Peter; Kromer, Bernd; Litt, Thomas; Lowe, David J.; Nakagawa, Takeshi; Newnham, Rewi; Schwander, Jacob (2009). "Formal definition and dating of the GSSP (Global Stratotype Section and Point) for the base of the Holocene using the Greenland NGRIP ice core, and selected auxiliary records" (PDF). Journal of Quaternary Science. 24 (1): 3–17. Bibcode:2009JQS....24....3W. doi:10.1002/jqs.1227. (PDF) from the original on 2013-11-04.
  20. ^ a b Dershowitz, Nachum; Reingold, Edward M. (2008). Calendrical Calculations (3rd ed.). Cambridge University Press. ISBN 978-0-521-70238-6.
  21. ^ "ICS chart containing the Quaternary and Cambrian GSSPs and new stages (v 2018/07) is now released!". Retrieved February 6, 2019.
  22. ^ Conners, Deanna (September 18, 2018). "Welcome to the Meghalayan age". Retrieved February 6, 2019.
  23. ^ Currie Lloyd A (2004). (PDF). Journal of Research of the National Institute of Standards and Technology. 109 (2): 185–217. doi:10.6028/jres.109.013. PMC 4853109. PMID 27366605. Archived from the original (PDF) on 2010-12-06. Retrieved 2018-06-24.

Sources edit

January 19, 2024
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YBP and ybp redirect here For other uses see YBP disambiguation Before Present BP years also known as time before present or years before present YBP is a time scale used mainly in archaeology geology and other scientific disciplines to specify when events occurred relative to the origin of practical radiocarbon dating in the 1950s Because the present time changes standard practice is to use 1 January 1950 as the commencement date epoch of the age scale The abbreviation BP has been interpreted retrospectively as Before Physics 1 which refers to the time before nuclear weapons testing artificially altered the proportion of the carbon isotopes in the atmosphere which scientists must now account for 2 3 In a convention that is not always observed many sources restrict the use of BP dates to those produced with radiocarbon dating the alternative notation RCYBP stands for the explicit radio carbon years before present Contents 1 Usage 1 1 SI prefixes 2 Radiocarbon dating 3 Radiocarbon calibration 4 Conversion 5 See also 6 Citations 7 SourcesUsage editThe BP scale is sometimes used for dates established by means other than radiocarbon dating such as stratigraphy 4 5 This usage differs from the recommendation by van der Plicht amp Hogg 6 followed by the Quaternary Science Reviews 7 8 both of which requested that publications should use the unit a for annum Latin for year and reserve the term BP for radiocarbon estimations Some archaeologists use the lowercase letters bp bc and ad as terminology for uncalibrated dates for these eras 9 The Centre for Ice and Climate at the University of Copenhagen instead uses the unambiguous b2k for years before 2000 CE not necessarily however often in combination with the Greenland Ice Core Chronology 2005 GICC05 time scale 10 Some authors who use the YBP dating format also use YAP years after present to denote years after 1950 11 SI prefixes edit SI prefix multipliers may be used to express larger periods of time e g ka BP thousand years BP Ma BP million years BP and many others 12 Radiocarbon dating editRadiocarbon dating was first used in 1949 13 14 Beginning in 1954 metrologists established 1950 as the origin year for the BP scale for use with radiocarbon dating using a 1950 based reference sample of oxalic acid According to scientist A Currie Lloyd The problem was tackled by the international radiocarbon community in the late 1950s in cooperation with the U S National Bureau of Standards A large quantity of contemporary oxalic acid dihydrate was prepared as NBS Standard Reference Material SRM 4990B Its 14C concentration was about 5 above what was believed to be the natural level so the standard for radiocarbon dating was defined as 0 95 times the 14C concentration of this material adjusted to a 13C reference value of 19 per mil PDB This value is defined as modern carbon referenced to AD 1950 Radiocarbon measurements are compared to this modern carbon value and expressed as fraction of modern fM Radiocarbon ages are calculated from fM using the exponential decay relation and the Libby half life 5568 a The ages are expressed in years before present BP where present is defined as AD 1950 15 The year 1950 was chosen because it was the standard astronomical epoch at that time citation needed It also marked 2 the publication of the first radiocarbon dates in December 1949 16 and 1950 also antedates large scale atmospheric testing of nuclear weapons which altered the global ratio of carbon 14 to carbon 12 17 Radiocarbon calibration editMain article Radiocarbon dating Calibration Dates determined using radiocarbon dating come as two kinds uncalibrated also called Libby or raw and calibrated also called Cambridge dates 18 Uncalibrated radiocarbon dates should be clearly noted as such by uncalibrated years BP because they are not identical to calendar dates This has to do with the fact that the level of atmospheric radiocarbon carbon 14 or 14C has not been strictly constant during the span of time that can be radiocarbon dated Uncalibrated radiocarbon ages can be converted to calendar dates by calibration curves based on comparison of raw radiocarbon dates of samples independently dated by other methods such as dendrochronology dating based on tree growth rings and stratigraphy dating based on sediment layers in mud or sedimentary rock Such calibrated dates are expressed as cal BP where cal indicates calibrated years or calendar years before 1950 Many scholarly and scientific journals require that published calibrated results be accompanied by the name standard codes are used of the laboratory concerned and other information such as confidence levels because of differences between the methods used by different laboratories and changes in calibrating methods Conversion editConversion from Gregorian calendar years to Before Present years is by starting with the 1950 01 01 epoch of the Gregorian calendar and increasing the BP year count with each year into the past from that Gregorian date For example 1000 BP corresponds to 950 CE 1949 BP corresponds to 1 CE 1950 BP corresponds to 1 BCE 2000 BP corresponds to 51 BCE Example milestone years in the BP time scale Gregorian year BP year Event9701 BC 11650 BP End of the Pleistocene and beginning of the Holocene epoch 19 4714 BC 6663 BP Epoch of the Julian day system Julian day 0 starts at Greenwich noon on January 1 4713 BC of the proleptic Julian calendar which is November 24 4714 BC in the proleptic Gregorian calendar 20 10 2251 BC 4200 BP Beginning of the Meghalayan age the current and latest of the three stages in the Holocene era 21 22 45 BC 1994 BP Introduction of the Julian calendar1 BC 1950 BP Year zero at ISO 8601AD 1 1949 BP Beginning of the Common Era and Anno Domini from the estimate by Dionysius of the Incarnation of Jesus1582 368 BP Introduction of the Gregorian calendar 20 47 1950 Epoch of the Before Present dating scheme 23 190 2024 74 YAP Current yearSee also editAnthropoceneCitations edit Flint Richard Foster Deevey Edward S 1962 Volume 4 1962 Radiocarbon 4 1 i a b Taylor RE 1985 The beginnings of radiocarbon dating in American Antiquity a historical perspective American Antiquity 50 2 309 325 doi 10 2307 280489 JSTOR 280489 S2CID 163900461 Dincauze Dena 2000 Measuring time with isotopes and magnetism Environmental Archaeology Principles and Practice Cambridge England Cambridge University Press p 110 ISBN 978 0 5213 1077 2 AGU Editorial Style Guide for Authors American Geophysical Union 21 September 2007 Archived from the original on 2008 07 14 Retrieved 2009 01 09 North American Commission on Stratigraphic Nomenclature November 2005 North American Stratigraphic Code Article 13 c The American Association of Petroleum Geologists Bulletin 89 11 1547 1591 doi 10 1306 07050504129 Archived from the original on 2014 02 02 Retrieved 2009 06 29 van der Plicht Johannes Hogg Alan 2006 A note on reporting radiocarbon PDF Quaternary Geochronology 1 4 237 240 doi 10 1016 j quageo 2006 07 001 S2CID 128628228 The use of time units in Quaternary Science Reviews Quaternary Science Reviews 26 9 10 1193 May 2007 Bibcode 2007QSRv 26 1193 doi 10 1016 j quascirev 2007 04 002 Wolff Eric W December 2007 When is the present Quaternary Science Reviews 26 25 28 3023 3024 Bibcode 2007QSRv 26 3023W doi 10 1016 j quascirev 2007 10 008 S2CID 131227900 Edward J Huth 25 November 1994 Scientific Style and Format The CBE Manual for Authors Editors and Publishers Cambridge University Press pp 495 ISBN 978 0 521 47154 1 Retrieved 4 October 2012 The GICC05 time scale Centre for Ice and Climate University of Copenhagen 3 September 2009 Archived from the original on 18 September 2018 Retrieved September 17 2018 Berger Andre 1988 Milankovitch Theory and Climate Reviews of Geophysics 26 4 624 657 doi 10 1029 RG026i004p00624 ISSN 8755 1209 Martin Kolling 2015 Numerous ways to say thousand years in a scientific paper Universitat Bremen Marine Geochemistry Laboratory Methods Retrieved 2023 03 24 Arnold J R Libby W F 1949 Age determinations by radiocarbon content checks with samples of known age Science 110 2869 678 680 Bibcode 1949Sci 110 678A doi 10 1126 science 110 2869 678 JSTOR 1677049 PMID 15407879 Aitken 1990 pp 60 61 Currie Lloyd A March April 2004 The Remarkable Metrological History of Radiocarbon Dating II PDF Journal of Research of the National Institute of Standards and Technology 109 2 185 217 doi 10 6028 jres 109 013 PMC 4853109 PMID 27366605 Archived from the original PDF on 2010 12 06 Retrieved 30 October 2019 The Remarkable Metrological History of Radiocarbon Dating II Archived 2023 01 01 at the Wayback Machine at Google Books accessed 30 October 2019 Arnold JR Libby WF 1949 03 04 Age determinations by radiocarbon content Checks with samples of known age Science 109 2827 227 228 Bibcode 1949Sci 109 227L doi 10 1126 science 109 2827 227 PMID 17818054 Nuclear Bombs Made It Possible to Carbon Date Human Tissue Smithsonian Magazine 2013 02 19 Retrieved 2020 01 09 Greene Kevin 2002 Archaeology An Introduction Philadelphia University of Pennsylvania Press pp 165 167 ISBN 0 8122 1828 0 Walker Mike Jonsen Sigfus Rasmussen Sune Olander Popp Trevor Steffensen Jorgen Peder Gibbard Phil Hoek Wim Lowe John Andrews John Bjorck Svante Cwynar Les C Hughen Konrad Kershaw Peter Kromer Bernd Litt Thomas Lowe David J Nakagawa Takeshi Newnham Rewi Schwander Jacob 2009 Formal definition and dating of the GSSP Global Stratotype Section and Point for the base of the Holocene using the Greenland NGRIP ice core and selected auxiliary records PDF Journal of Quaternary Science 24 1 3 17 Bibcode 2009JQS 24 3W doi 10 1002 jqs 1227 Archived PDF from the original on 2013 11 04 a b Dershowitz Nachum Reingold Edward M 2008 Calendrical Calculations 3rd ed Cambridge University Press ISBN 978 0 521 70238 6 ICS chart containing the Quaternary and Cambrian GSSPs and new stages v 2018 07 is now released Retrieved February 6 2019 Conners Deanna September 18 2018 Welcome to the Meghalayan age Retrieved February 6 2019 Currie Lloyd A 2004 The Remarkable Metrological History of Radiocarbon Dating II PDF Journal of Research of the National Institute of Standards and Technology 109 2 185 217 doi 10 6028 jres 109 013 PMC 4853109 PMID 27366605 Archived from the original PDF on 2010 12 06 Retrieved 2018 06 24 Sources editAitken M J 1990 Science based Dating in Archaeology London Longman ISBN 978 0 582 49309 4 Retrieved from https en wikipedia org w index php title Before Present amp oldid 1195270222, wikipedia, wiki, book, books, library,

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