1 history of radiocarbon dating origins: willard f. libby (1908-1980) 1. 1927-1940 libby at uc...

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HISTORY OF RADIOCARBON DATINGHISTORY OF RADIOCARBON DATING

ORIGINS: Willard F. Libby (1908-1980)ORIGINS: Willard F. Libby (1908-1980)

1. 1927-1940 Libby at UC Berkeley: In the Beginning1. 1927-1940 Libby at UC Berkeley: In the Beginning

2. 1940-1945 Libby at Columbia: The War Years2. 1940-1945 Libby at Columbia: The War Years

3. 1945-1952 Libby at Chicago: Three Critical Experiments3. 1945-1952 Libby at Chicago: Three Critical Experiments

DEVELOPMENTDEVELOPMENT

4. 1952-1960 First Radiocarbon Revolution4. 1952-1960 First Radiocarbon Revolution

5. 1960-1980 Second Radiocarbon Revolution: Calibration5. 1960-1980 Second Radiocarbon Revolution: Calibration

6. 1980- Third Radiocarbon Revolution: AMS 6. 1980- Third Radiocarbon Revolution: AMS

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1927-19401927-1940Libby at BerkeleyLibby at Berkeley

In the Beginning . . .In the Beginning . . . Undergraduate (Chemistry): 1927-1931 »

Graduate (Physical Chemistry): 1931-1933

Early 1930s: Early 1930s: 1414C = a “minor radioisotope”C = a “minor radioisotope” assumed short half life (< 1 year)assumed short half life (< 1 year) artificially produced before detected in natureartificially produced before detected in nature recoil tracks used to calibrate cloud chamber recoil tracks used to calibrate cloud chamber

experimentsexperiments favored production mechanism: deuterons [nuclei of favored production mechanism: deuterons [nuclei of

deuterium, an isotope of hydrogen] on deuterium, an isotope of hydrogen] on 1313CC

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Ernest O. LawrenceErnest O. Lawrence 1939 Nobel Prize in Physics1939 Nobel Prize in Physics

1414C: “A radioisotope C: “A radioisotope with biomedical with biomedical promise”promise”

long half life (>1000 long half life (>1000 years)years)

favored production favored production mechanism: neutrons mechanism: neutrons on on 1414NN

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Serge A. Korff (New York Serge A. Korff (New York University) cosmic ray University) cosmic ray physics experimentsphysics experiments

increase in neutrons with increase in neutrons with increasing altitudeincreasing altitude

neutrons created by neutrons created by cosmic rayscosmic rays

natural atmospheric natural atmospheric 1414C C production by neutron production by neutron secondariessecondaries

Korff and Danforth (1939) Korff and Danforth (1939) Physical ReviewPhysical Review

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UCB Ph.D. (1933) nuclear UCB Ph.D. (1933) nuclear chemistrychemistry

Built first Geiger counter Built first Geiger counter » in U.S. in U.S.

Dissertation: Weak beta Dissertation: Weak beta » activity in rare earth activity in rare earth elementselements

Known at UCB as "Wild Bill Known at UCB as "Wild Bill Libby" for pushing "far Libby" for pushing "far out" ideasout" ideas

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Screen-wall counter design: problem of Screen-wall counter design: problem of detecting betas close to background detecting betas close to background »

counter envelope glasscounter envelope glass wire grid (“screen-wall”) cathode: define wire grid (“screen-wall”) cathode: define

sensitive volumesensitive volume sample applied to inside surface of glass sleevesample applied to inside surface of glass sleeve glass sleeve moved in and out of sensitive glass sleeve moved in and out of sensitive

volumevolume mechanical mechanism for alteration of mechanical mechanism for alteration of

» background and sample countingbackground and sample counting Basic design of detector used in post Basic design of detector used in post

World War II World War II 14CC experimentsexperiments

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Late 1930s:Late 1930s: 1414C half life >1000 C half life >1000

years (10years (1033-10-105 5 years)years) Favored production: Favored production:

neutrons on neutrons on 1414NN Libby reads Korff and Libby reads Korff and

Danforth (1939)Danforth (1939) Libby: “That’s Libby: “That’s »

Radiocarbon Radiocarbon Dating!”Dating!”

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Radiocarbon dating: Basic Radiocarbon dating: Basic physical model (1939)physical model (1939) production in atmosphere as production in atmosphere as

1414COCO22

photosynthetic fixing in photosynthetic fixing in biospherebiosphere

living biosphere living biosphere 1414C C equilibriumequilibrium

death withdrawal from death withdrawal from exchangeexchange

time since death function of time since death function of residual residual 1414C concentrationC concentration

No experimental No experimental confirmationconfirmation

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1940-19451940-1945Libby at Columbia: The War YearsLibby at Columbia: The War Years

Research on hold during esearch on hold during World War II.World War II.

1940-1945: Manhattan 1940-1945: Manhattan ProjectProject With Harold Urey [1934 Nobel With Harold Urey [1934 Nobel

Prize in chemistry] at Prize in chemistry] at Columbia UniversityColumbia University

developing a thermal diffusion developing a thermal diffusion method to separate method to separate 235235U from U from 238238UU

later thought this research as later thought this research as the high point of his scientific the high point of his scientific careercareer

Requested Requested 1414C half-life C half-life measurement at Argonne: measurement at Argonne: 26,00026,000±± 13,000 and 21,000 13,000 and 21,000±± 4000 years4000 years

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1414C: A dating isotope? C: A dating isotope? Testing implications of Testing implications of modelmodel

1946-1952: University of Chicago1946-1952: University of ChicagoWith Harold Urey in the With Harold Urey in the Institute of Nuclear StudiesInstitute of Nuclear Studies Libby (1946) Libby (1946) Physical ReviewPhysical Review: : first published description of first published description of concept: coined term concept: coined term "radiocarbon""radiocarbon"

With first Chicago graduate With first Chicago graduate student Ernest C. Anderson: student Ernest C. Anderson: First Critical Experiment: First Critical Experiment: isotopic enrichment documented isotopic enrichment documented difference in difference in 1414C activity between C activity between modern biomethane and fossil modern biomethane and fossil petromethanepetromethane

1945-19521945-1952Libby at Chicago: Three Critical ExperimentsLibby at Chicago: Three Critical Experiments

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1945-19521945-1952Libby at Chicago: The Critical ExperimentsLibby at Chicago: The Critical Experiments

1414C: A dating isotope?C: A dating isotope? Testing implications of modelTesting implications of model

James Arnold joins group as James Arnold joins group as » Postdoctoral FellowPostdoctoral Fellow

Decay counting using solid Decay counting using solid » carbon in a modified Geiger carbon in a modified Geiger counter of Libby's Berkeley counter of Libby's Berkeley designdesign

Critical technical developmentCritical technical development: : Electronic anticoincidence Electronic anticoincidence » shielding for low level counting shielding for low level counting close to backgroundclose to background Made decay counting Made decay counting 1414C C

dating practical dating practical Second Critical ExperimentSecond Critical Experiment: :

Anderson dissertation: Anderson dissertation: 1414C C activities in living samples from activities in living samples from various latitudes were various latitudes were » essentially equal (exception: essentially equal (exception: marine shell)marine shell)

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1947-48: 1947-48: Third Critical Third Critical experimentexperiment

First First 1414C date: wood from tomb of C date: wood from tomb of Zoser (Djoser), 3rd Dynasty Zoser (Djoser), 3rd Dynasty Egyptian king (July 12, 1948).Egyptian king (July 12, 1948). Historic age: 4650±75 BPHistoric age: 4650±75 BP Radiocarbon age: (C-1) Radiocarbon age: (C-1)

3979±350 BP [average of 3 3979±350 BP [average of 3 determinations 3699±770, determinations 3699±770, 4234±600, 3991±500]4234±600, 3991±500]

Second Second 1414C date: wood from C date: wood from Hellenistic coffin Hellenistic coffin Historic age: 2300±200 BPHistoric age: 2300±200 BP Radiocarbon age: (C-?) Radiocarbon age: (C-?)

Modern! Fake!Modern! Fake! First “Curve of Knowns”:First “Curve of Knowns”:

6 data points (using seven 6 data points (using seven samples) spanning AD 600 to samples) spanning AD 600 to 2700 BC.2700 BC.

Half life used: 5720±Half life used: 5720± 47 years47 years

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1948: Adaption of screen-wall counter design using elemental (solid) carbon

CO2 from combustion/acidification reduced by reaction with magnesium at high temperature and separation of MgO ("ash") from elemental carbon ("lamp black") by treating with concentrated HCl.

Inside surface of sleeve of screen-wall counter coated with elemental carbon: The Procedure from Hell!

Construction of large scale (3 story high) thermal diffusion column in case routine screen-wall counter operation not achieved; column never used

Destruction of set of counters when crushed under weight of magnets of new accelerator being installed

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1949: Critical Experiments Successful “The agreement between prediction and

observation is seen to be satisfactory." Average overall errors on ages = ±10%

Foundation 14C paper: Arnold and Libby "Age determinations by radiocarbon content: checks with samples of known age." Science, December 23, 1949.

Birthday of Radiocarbon Dating

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1945-1952 1945-1952

Libby at ChicagoLibby at Chicago

Chicago Radiocarbon Laboratory operational: 1949-1952

554 samples measured and published in a series of “date lists.”

First Chicago list (September 1, 1950): 148 14C dates. » Published with minor modifications in Science in February 1951 (Arnold and Libby 1951) using new “Libby half life” = 5568±30 yrs.

First Revised "Curve of Knowns" substituted Libby t1/2

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1952-1960 1952-1960 First Generation Labs First Generation Labs

Libby appointed to Atomic Energy Commission (1952)Libby appointed to Atomic Energy Commission (1952)

1st International Radiocarbon Conferences: Copenhagen and 1st International Radiocarbon Conferences: Copenhagen and Andover (1954). [No proceedings published until 6th in Andover (1954). [No proceedings published until 6th in Pullman 1965]Pullman 1965]

Second Revised "Curve of Knowns" had eleven data points Second Revised "Curve of Knowns" had eleven data points » included "Bible" [(wrappings from Dead Sea Scrolls] (Libby, included "Bible" [(wrappings from Dead Sea Scrolls] (Libby, Radiocarbon DatingRadiocarbon Dating, 2nd edition, 1955), 2nd edition, 1955)

First Generation (solid carbon) Labs: Arizona*, Michigan*, First Generation (solid carbon) Labs: Arizona*, Michigan*, Pennsylvania,* Yale, Lamont (Columbia), New Zealand, Pennsylvania,* Yale, Lamont (Columbia), New Zealand, Copenhagen, Saskatchewan. [* archaeologists instrumental in Copenhagen, Saskatchewan. [* archaeologists instrumental in establishing] establishing]

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1952-1960 1952-1960 First Generation LabsFirst Generation Labs

Obsolescence of solid carbon: nuclear fallout. » Conversion to or development of gas proportional and » liquid scintillation counting labs: e.g., U.S.G.S., Scripps (UC San Diego), Groningen, British Museum, Cambridge, Stockholm, Uppsala

1959: Journal Radiocarbon begins publication as annual Radiocarbon Supplement to American Journal of Science publishing date lists, separate standing as Radiocarbon from 1963. From 1989, Radiocarbon: An International Journal of Cosmogenic Isotope Research

1960: Nobel Prize in Chemistry: "for his method to use Carbon-14 for age determinations in archaeology, geology, geophysics, and other sciences." Libby had arrived at UCLA in late 1959, established Isotope Laboratory in Institute of Geophysics and Planetary Physics

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1960 Nobel Prize in Chemistry1960 Nobel Prize in Chemistry

““At its meeting of November 3, At its meeting of November 3, 1960, the Royal Swedish Academy 1960, the Royal Swedish Academy of Science has decided, in of Science has decided, in conformity with the terms of the conformity with the terms of the November 27, 1895 will of Alfred November 27, 1895 will of Alfred Nobel, to award the prize to be Nobel, to award the prize to be given this year for the most given this year for the most important chemical discovery or important chemical discovery or improvement to Willard F. Libby improvement to Willard F. Libby for his method to use Carbon-14 for his method to use Carbon-14 for age determinations in for age determinations in archaeology, geology, geophysics archaeology, geology, geophysics and other sciences.” and other sciences.”

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1960-1980 1960-1980

“Second Radiocarbon Revolution:” Calibration“Second Radiocarbon Revolution:” Calibration

Calibration: Violation of assumption of constant biospheric "zero age" 14C activity First test: 1949: First “Curve of Knowns”: "satisfactory

agreement" to 5000 BP with overall precision of ±10% Increased counting sensitivities: 1960: additional

Egyptian Old Kingdom (ca. 3000-2100 BC) samples "too young" by 500-600 yrs at 3000 BC. Libby (1963) suggested that conventional reconstruction of ancient Egyptian chronology by contemporary Egyptologists was in error rather than 14C-inferred ages.

First detailed study: 1960: Using tree ring series and » proportional gas counters with ±1% (±80 yrs) counting variances. Existence of systematic offsets of up to about 160 years over last 1300 years.

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1960-1980 1960-1980

“Second Radiocarbon Revolution:” Calibration “Second Radiocarbon Revolution:” Calibration Calibration of 14C time scale: Distinguishing “real (solar, sidereal)

time" and "14C time” Bristlecone pine / 14C data: First detailed continuous tree ring- »

based data set documenting 14C offsets over last 7000 yrs. (Sues » 1970). Documents: (1) major or long-term trend (apparent sine- wave function) and (2) complex set of shorter-term/higher- frequency variations.

Long-term anomaly: maximum Holocene offset about 10% or » 800 years at about 7000 BP

Shorter-term anomalies: “De Vries effects” multi-millennial » and multi-century oscillations in 14C time spectrum ("wiggles," "kinks," "warps") = accordion-like characteristics of 14C time scale. At some time periods in Holocene, 14C time resolution is inherently temporally "blinded" for various intervals irrespective of counting variance on sample measurement.

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1977

Conventional Radiocarbon Age: Definition

Stuiver and Polach (1977) Reporting of 14C Data. Radiocarbon

1. Use Libby half-life (5568 years) 2. Use 0.95 NBS Oxalic Acid I [or standards with known

relationship] to define “zero” age 14C count rate 3. Use A.D. 1950 as 0 BP. [BP = “Before Physics”] 4. Normalize 14C activity to common δ13C value = -25.0 ‰ 5. Uncalibrated

Defines “radiocarbon time” expressed in “14C years”

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1980-present 1980-present Third Radiocarbon Revolution: AMSThird Radiocarbon Revolution: AMS

Pre-AMSPre-AMS

1970: Late Hans Oeschger (Bern) first noted great 1970: Late Hans Oeschger (Bern) first noted great » increase in sensitivity that would be possible from ion increase in sensitivity that would be possible from ion counting using isotopic enrichment and mass counting using isotopic enrichment and mass spectrometry.spectrometry.

1974-77: Michael Anbar [SUNY Buffalo] (1978) reports an 1974-77: Michael Anbar [SUNY Buffalo] (1978) reports an effort undertaken earlier at Stanford Research Institute to effort undertaken earlier at Stanford Research Institute to use conventional mass spectrometry to measure CNuse conventional mass spectrometry to measure CN-- for for natural level natural level 1414C detection. C detection.

Backgrounds from mass 29 trace impurities prevented the Backgrounds from mass 29 trace impurities prevented the approach from becoming feasible for routine work. Ran approach from becoming feasible for routine work. Ran out of funds. out of funds.

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1970-19801970-1980Third Radiocarbon Revolution: AMSThird Radiocarbon Revolution: AMS

Cyclotron AMS

1976-1977: Richard Muller [UC Berkeley] (1977) examined a cyclotron-based AMS technique, principle of using particle accelerator charge-to-mass filter first demonstrated by Luis Alvarez in 1939 in detecting 3He.

Berkeley "high energy mass spectrometry" (HEMS) » combined cyclotron for mass resolution and range » separation of 14N from 14C using a xenon cell.

Suggested extension of 14C time frame to 106 years with AMS if contamination free sample could be prepared.

First published AMS-based 14C date. » 1980's: Muller's group unsuccessful attempt to develop a 40 »

keV "cyclotrino" for routine 14C measurements using external ion source. (Shanghai group successful in 1990s)

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1977-19801977-1980Third Radiocarbon Revolution:Third Radiocarbon Revolution: AMS AMS

Tandem AMS

1977: Rochester-Toronto-General Ionex (Purser et al.) ° and Simon Frazer-McMaster (Nelson et al.) groups essentially simultaneously employed tandem accelerators using negative ions to detect natural level 14C.

History of science footnote: Harry Gove (Rochester group) argues that "Rochester Tandem experiment produced the first ever carbon-14 date by accelerator mass spectrometry, since we made a background measurement on graphite. The work at Rochester had been carried out two weeks before that at McMaster but they beat us by one day in getting their manuscript to the publisher [Science].”

1978: First Conference on Radiocarbon Dating with Accelerators, University of Rochester.

Initial AMS spectrometers previously used for nuclear » structure, refitted for AMS work. First dedicated AMS » instrument: University of Arizona. »

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Radiocarbon Dating Impact: ArchaeologyRadiocarbon Dating Impact: Archaeology

1948-1970 “First Radiocarbon Revolution” 1948-1970 “First Radiocarbon Revolution” °°

1414C dating constitutes the “great revolution in C dating constitutes the “great revolution in 2020thth century prehistoric studies” Glyn Daniel century prehistoric studies” Glyn Daniel

Development of Development of 1414C dating in 20C dating in 20thth century century comparable to discovery of antiquity of the comparable to discovery of antiquity of the human species in the 19human species in the 19thth century century

Made a world-wide chronometric framework for Made a world-wide chronometric framework for prehistory possible prehistory possible

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Chronology of the Peopling of the New WorldChronology of the Peopling of the New World Advent of Advent of 1414C dating transformed C dating transformed

approaches to the dating frameworks for approaches to the dating frameworks for Paleoindian and Paleoamerican studiesPaleoindian and Paleoamerican studies

History of the application of History of the application of 1414C data in C data in Paleoindian / Paleoamerican contexts Paleoindian / Paleoamerican contexts provide classic case studies of some of the provide classic case studies of some of the issues and problems encountered in the issues and problems encountered in the critical application of the critical application of the 1414C methodC method

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Chronology of the Peopling of the New WorldChronology of the Peopling of the New World

Folsom sites 14C age BP

_____________________________

Hanson (4)Hanson (4) 10,290 10,290±±9090 Carter/Kerr McGeeCarter/Kerr McGee 10,400 10,400±±600600

Lubbock LakeLubbock Lake 10,540 10,540±±100100 Indian Creek/1Indian Creek/1 10,630 10,630±±280280 Owl Cave Owl Cave 10,640 10,640±±8585

Lindenmeier (3) Lindenmeier (3) 10,660 10,660±±60 60 Agate Basin (2) Agate Basin (2) 10,700 10,700±±70 70 Folsom (6)Folsom (6) 10,890 10,890±±5050 Indian Creek/2 Indian Creek/2 10,980 10,980±±150150

[20 [20 1414C values from 8 sites]C values from 8 sites]

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Chronology of the Peopling of the New WorldChronology of the Peopling of the New World

Clovis sites 14C age BP__________________________________

Murray Springs (8)Murray Springs (8) 10,89010,890±±5050Lehner (12)Lehner (12) 10,94010,940±±4040Anzick Anzick 10,94010,940±±9090DentDent 10,98010,980±±9090UP MammothUP Mammoth 11,28011,280±±350350Lange/FergusonLange/Ferguson 11,14011,140±±140140ColbyColby 11,20011,200±±220220DomeboDomebo 11,48011,480±±450 450 Blackwater Draw(3)Blackwater Draw(3) 11,30011,300±±240240Aubrey (2)Aubrey (2) 11,57011,570±±7070

[31 [31 1414C values from 10 sites]C values from 10 sites]

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Radiocarbon Dating Impact: ArchaeologyRadiocarbon Dating Impact: ArchaeologyChronology of the Peopling of the New WorldChronology of the Peopling of the New World

Initial DataInitial Data

Tule Springs, NevadaTule Springs, Nevada: >23,800 : >23,800 1414C years BP (C-914) C years BP (C-914) on what was characterized as charcoal recovered on what was characterized as charcoal recovered from what had been identified as a "hearth-like from what had been identified as a "hearth-like feature" by excavators who associated its feature" by excavators who associated its occurrence with sediments containing the bones of occurrence with sediments containing the bones of extinct Pleistocene fauna [1953]extinct Pleistocene fauna [1953]

Old Crow, Yukon Territory, CanadaOld Crow, Yukon Territory, Canada: 27,000: 27,000+3000+3000//-2000-2000 1414C years BP (GX-1640) on an inorganic fraction C years BP (GX-1640) on an inorganic fraction ("bone mineral apatite") of a bone artifact [1973]("bone mineral apatite") of a bone artifact [1973]

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Revised DataRevised Data

Tule SpringsTule Springs: "charcoal" determined to be decayed : "charcoal" determined to be decayed plant remains and "hearths" determined to be plant remains and "hearths" determined to be water channel or spring deposit structures. Oldest water channel or spring deposit structures. Oldest artifact(s): 10,000-11,000 artifact(s): 10,000-11,000 1414C years BP based on C years BP based on over 100 over 100 1414C dates from site [1974]C dates from site [1974]

Old CrowOld Crow: an organic fraction of the bone artifact : an organic fraction of the bone artifact yielded an age of 1350±150 yielded an age of 1350±150 1414C years BP (RIDDL-C years BP (RIDDL-145) [1986]145) [1986]

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New World human skeletonsNew World human skeletonsoriginal age assignmentoriginal age assignment

skeleton basis ageskeleton basis age__________________________________________________________

Sunnyvale AARSunnyvale AAR** 70,000 70,000

Del MarDel Mar AAR AAR** 41,000-48,000 41,000-48,000

Los Angeles Los Angeles 1414C >23,000C >23,000

AARAAR** 26,000 26,000

TaberTaber geologic 22,000-60,000 geologic 22,000-60,000

YuhaYuha 1414CC 22,00022,000

AARAAR* * 23,000 23,000

Laguna Laguna 14 14C 17,150 C 17,150

__________________**amino acid racemizationamino acid racemization

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New World human skeletons:New World human skeletons:original age assignmentoriginal age assignment

skeleton basis ageskeleton basis age__________________________________________________________

Sunnyvale AARSunnyvale AAR** 70,000 70,000

Del MarDel Mar AAR AAR** 41,000-48,000 41,000-48,000

Los Angeles Los Angeles 1414C >23,000C >23,000

AARAAR** 26,000 26,000

TaberTaber geologic 22,000-60,000 geologic 22,000-60,000

YuhaYuha 1414CC 22,00022,000

AARAAR* * 23,000 23,000

Laguna Laguna 14 14C 17,150 C 17,150

__________________**amino acid racemizationamino acid racemization

New World human skeletons: New World human skeletons: revised age assignmentrevised age assignment

basisbasis age age ______________________________________________________

1414CC** 3600-63003600-6300

1414CC** 49004900 1414CC** 35603560

1414CC** 35503550

1414CC** 1650-38501650-3850

1414CC** 51005100

____________________

** AMS-based on organic fraction AMS-based on organic fraction

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skeletonskeleton 1414C values (BP) referenceC values (BP) reference __________

Tlapacoya I, Mexico 10,200Tlapacoya I, Mexico 10,200±±65 Gonzalez et al. 2003 65 Gonzalez et al. 2003

Arroyo Frias, Argentina 10,300Arroyo Frias, Argentina 10,300±±60 Hicks, per. comm. 199560 Hicks, per. comm. 1995

Buhl, Idaho 10,675Buhl, Idaho 10,675±±95 Green 95 Green et alet al. 1998. 1998

PePeñoñon III, Mexico 10,775n III, Mexico 10,775±±75 Gonzalez et al. 200375 Gonzalez et al. 2003

Anzick, Montana 10,940Anzick, Montana 10,940±±90 Stafford 90 Stafford et alet al. 1991. 1991

Arlington Springs, California 10,960Arlington Springs, California 10,960±±8080 Johnson Johnson et alet al. 2000 . 2000 Naharon I, Mexico 11,670Naharon I, Mexico 11,670±±6060* * unpublishedunpublished____________________________________________________________________________________________________________________________

** 1414C measurement on non-collagen-like amino acids; minimum age (?)C measurement on non-collagen-like amino acids; minimum age (?)

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Kennewick, Washington human skeletonKennewick, Washington human skeleton

Sample boneSample bone bone bone fraction fraction 1414C age (BP) C age (BP) δδ1313C(C(‰)‰) preservationpreservation

______________________________________________________________________________________________________________________________________________

55thth left metcarpal 68.8%(C) left metcarpal 68.8%(C)11 TAA TAA33 84108410±±606055 -14.9 -14.911stst right metacarpal 0.3% right metacarpal 0.3%22 BETAI BETAI44 84108410±±404066 -12.6 -12.6 11stst right metacarpal 14.3%(NC) right metacarpal 14.3%(NC)11 TAA TAA33 81308130±±404055 -10.8 -10.8Left tibial crestLeft tibial crest 2.3%(NC) 2.3%(NC)11 TAA TAA33 69406940±±303055 -10.3 -10.3Left tibial crestLeft tibial crest 0.05% 0.05%22 gelatin gelatin 57505750±±10010077 -21.9 -21.9______________________________________________________________________________________________________________________________________________11% of modern bone standard amino acid content, C= collagen-like amino acid % of modern bone standard amino acid content, C= collagen-like amino acid composition. composition. 22percent carbon yield. percent carbon yield. 3 3 TAA = total amino acid. TAA = total amino acid. 4 4 Base extracted acid Base extracted acid insoluble. insoluble. 5 5 UC Riverside sample prep/Lawrence Livermore National Laboratory UC Riverside sample prep/Lawrence Livermore National Laboratory AMS measurement. AMS measurement. 66 Beta Analytic. Beta Analytic. 77 University of Arizona accelerator University of Arizona accelerator

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Radiocarbon dating continues to be the “gold Radiocarbon dating continues to be the “gold standard” for assigning age to Holocene and late standard” for assigning age to Holocene and late Pleistocene archaeological, geological, and Pleistocene archaeological, geological, and paleontological contextspaleontological contexts

Late UCB Prehistorian J. Desmond Clark: Without Late UCB Prehistorian J. Desmond Clark: Without the the 1414C time scale, prehistorians would be C time scale, prehistorians would be “foundering in a sea of imprecisions sometimes bred “foundering in a sea of imprecisions sometimes bred of inspired guesswork but more often of imaginative of inspired guesswork but more often of imaginative speculation.”speculation.”

endend

1 history of radiocarbon dating origins: willard f. libby (1908-1980) 1. 1927-1940 libby at uc...

Documents

c production

c slide

n libby

c favored production

c half life

berkeley radiocarbon

wild bill libby

radiocarbon revolution