Radiocarbon dating

Elisabetta Boaretto

Radiocarbon Dating and Cosmogenic Isotopes Laboratory

The Martin (Szusz) Department of Land of Israel Studies and Archaeology

Bar Ilan University

and

Kimmel Center for Archaeological Science

Weizmann Institute of Science

Walter KutscheraVienna Environmental Research Accelerator (VERA) Laboratory

Faculty of Physics – Isotope Research

University of Vienna

Synchronizing Clocks at ArmageddonWorkshop on Archaeological Dating

Megiddo, Israel, 20-22 June 2010

General Introduction to Radiocarbon

Standard Radiocarbon Dating

14Ct = 14CO e-λλλλt

t = 1/λλλλ x ln(14CO/ 14Ct)

t = t1 /2 /ln2 x ln(14CO/ 14Ct)

Conditions:

• 14CO must be known for all times. Because material of known age

(tree rings) is available back to about 12,500 years B.P., 14CO is well

calibrated for this period. Beyond this, the calibration has larger

uncertainties, but does exist now back to 50,000 years.

[Reimer et al., INTCAL09, Radiocarbon, 51/4 (2009) 1111-1150]

• t1 /2 need not to be known accurately, because the14C determination

– the uncalibrated, so-called ‘radiocarbon age‘ – is performed with

exactly the same procedure in unknown samples as in the tree-ring samples. The latter delivers the translation of the uncalibrated

radiocarbon age into a calendar date.

Absolute Radiocarbon Dating14Ct →→→→ 14N* + e- + ννννe

Total energy release: 156 keV

Maximum recoil energy of 14N*: 7.3 eV

_________________________________

14Ct = 14CO e-λλλλt = (14Ct + 14N* ) e-λλλλt

t = 1/λλλλ x ln(1 + 14N*/14Ct)

t = t1/2/ln2 x ln(1 + 14N*/14Ct)

Conditions:

• 14Ct and 14N* must be measured

• t1/2 must be accurately known

• 14CO need not to be known

12C12C 14C

12C 12C

12C

12C12C 14N*

12C 12C

12C

Benzene Pyridine

Change of chemical compound by in-situ decay of 14C

Reference: “An attempt at absolute 14C dating“, Jacob Szabo and

Israel Carmi (Weizmann Institute), Dror Segal and Eugenia Mintz

(Israel Antiquities Authority), Radiocarbon 40/1 (1998) 77-83.

O3 + hνννν →→→→ O2 + O(1D)

O(1D) + H2O →→→→ 2OH•

OH•/O2 ~ 10-13!

12,000 10,000 7500 5000 2500 0

Years before present

Reference value: 14C/12C = 1.2x10-12

Subfossil pine out of a gravel pit near Tapfheim, Danube river, grown11,200 years before present (BP).(B. Kromer, Universityof Heidelberg)

Natural 14C variations

14C Bomb Peak

Variation of the 14C content in atmospheric CO2

during the last 4000 Years

Long-term observations of ∆∆∆∆14C in atmospheric CO2

in the northern and in the southern hemisphereLevin and Hesshaimer, Univ. Heidelberg, Radiocarbon 42/1 (2000) 69

Natural 14C level

NTBT 1963

14C decay (t1/2 = 5740 a)

The Iceman “Ötzi“ two days after his discovery (Sept. 1991), emerging from an ice patch at 3120 m a.s.l. in the Ötztal Alps at the Austrian/Italian border

Bow

14C dating of bone and tissuefrom the Iceman Ötzi at theAMS labs of Oxford and Zürich in 1992

Uncalibrated (radiocarbon) age:4550 ± 19 yr BP (before present)

Calibrated age range:5300 to 5050 BP

Direct dating of Early Upper Paleolithic human remains from the Mladeč Caves in Moravia (Czech Republic)

Eva Maria Wild et al., Nature 435 (2005) 322

Sampled areas for 14C measurements at VERA

Radiocarbon ages determined for the human remains from the Mladeč site in Moravia (Czech Republic)

_____________________________________________________________________________

Lab Number Sample Name Sample material 14C-age(years BP)

_____________________________________________________________________________

VERA-2736 Mladeč 25c Ulna 26,330 ± 170

VERA-3073 Mladeč 1 Right molar M2 31,190 ± 400distal half of the crown

VERA-3074 Mladeč 2 Left molar M3 31,320 ± 400distal half of the crown

VERA-3075 Mladeč 8 Left molar M2 30,680 ± 380mesial-buccal root

VERA-3076A Mladeč 9a Right maxillary canine, Lingual half 31,500 ± 410of the root (white-coloured collagen)

VERA-3076B Mladeč 9a Right maxillary canine, Lingual half 27,370 ± 230of the root (brown-coulored collagen)

_____________________________________________________________________________

Radiocarbon calibration from 23,000 to 47,000 years BP (before present)E. Bard et al., A Better Radiocarbon Clock, Science 303 (2004) 178

Radiocarbon-Based Chronology for Dynastic Egypt

C. Bronk Ramsey, M. W. Dee, J. M. Rowland, T. F. G. Higham, F. Brock

Research Laboratory for Archaeology and the History of Art, University of Oxford, UK

S. A. Harris

Department of Plant Sciences, University of Oxford, UK

A. Quiles

Laboratoire de Mesure du Carbone 14, CEA, Saclay, France

E. M. Wild

Vienna Environmental Research Accelerator, University of Vienna, Austria

E. S. Marcus

The Recanati Institute for Maritime Studies, University of Haifa, Israel

A. J. Shortland

Centre for Archaeological and Forensic Analysis, Cranfield University, UK

SCIENCE, 328 (18 June 2010) 1554-1557

Comparison of Pharao accession dates from the Historical Chronology of Egypt(marked in red, blue and green) for the Old Kingdom (A), the Middle Kingdom (B)

and the New Kingdom with sequenced radiocarbon dates.

Distribution of uncalibrated radiocarbon dates against the modeled age,together with the calibration curve. Outliers are indicated in light gray.Total of 211 14C measurements, 188 accepted (23 outliers).

Investigating the likelihood of a reservoir offset in theradiocarbon record for ancient Egypt

M. W. Dee, F. Brock, C. Bronk Ramsey, T. F. G. Higham, J. M. Rowland,

Research Laboratory for Archaeology and the History of Art, University of Oxford, UK

S. A. Harris

Department of Plant Sciences, University of Oxford, UK

A. J. Shortland

Centre for Archaeological and Forensic Analysis, Cranfield University, UK

AMS radiocarbon measurements were made on 66 known-age samples of

short-lived plant species collected in Egypt between 1700 and 1900 AD.

Journal of Archaeological Science, 37 (2010) 687-693

Comparison between yearly averages and calibration curve values. An average offset of 19 ± 5 years was obtained.

Investigating the likelyhood of a reservoir offset in the radiocarbon record for ancient Egypt, Dee et al., J. Archaeol. Sci 37 (2009) 687-693

14C AMS measurements at Oxford of 66 short-

lived plants grown in Egypt between 1702 and

1881 resulted in an offset of 19 ± 5 years.

Regional offset in radiocarbon dates from the calibration curve(A) Modeled result (dark gray) with input of offset = 19 ± 5 yr (light gray)

(B) Modeled result (dark gray) with no input offset = 0 ± 10 yr (light gray)

A brief introduction to VERA,

the Vienna Environmental Research Accelerator

WIEN___________0.5 km

VERA

1.5 km

VERA 1993

Währinger Straße 17

Wolfgang AmadeusMozart composedhere Cosi fan tutte

in 1790

VERA 1993

Wolfgang AmadeusMozart composedhere Cosi fan tutte

in 1790

Ludwig van Beethovendied here in 1827

VERA 1993

Wolfgang AmadeusMozart composedhere Cosi fan tutte

in 1790

Ludwig van Beethovendied here in 1827

VERA 1993

800 m to birth place of

Franz Schubert, 1799

Wolfgang AmadeusMozart composedhere Cosi fan tutte

in 1790

Ludwig van Beethovendied here in 1827

500 m down this road,

Sigmund Freud livedfrom 1891 to 1938

VERA 1993

800 m to birth place of

Franz Schubert, 1799

Wolfgang AmadeusMozart composedhere Cosi fan tutte

in 1790

Ludwig van Beethovendied here in 1827

500 m down this road,

Sigmund Freud livedfrom 1891 to 1938

VERA 1993

Victor Hess discoveredCosmic radiation in 1912

800 m to birth place of

Franz Schubert, 1799

Primary cosmic ray (proton)

Victor HessBaloon flights

in 1912 up to 5000 m

Victor F. Hess shared the 1936 Nobel Prize in Physics (for thediscovery of cosmic rays) withCarl D. Anderson (for thediscovery of the positron)

Willard F. Libby (1905-1980)

1960 Nobel Prize in Chemistry

“for his method to use carbon-14

for age determination in

archaeology, geology, geophysics,

and other branches of science“

Photo by Fabian Bachrach circa 1952

12 April 2007

14Co

14Ct = 14Co e-λλλλt

Age determination by radiocarbon content: checks with samples of known age

James R. Arnold and Willard F. Libby, Science 110 (1949) 678-680

Isotope abundances of some light elements

Hydrogen 1H 99.985 %2H(D) 0.015 %

Carbon 12C 98.900 %

13C 1.100 %

14C 0.000 000 000 1 % (t1/2 = 5 730 a)

Nitrogen 14N 99.634 %15N 0.366 %

Oxygen 16O 99.762 %17O 0.038 %18O 0.200 %

6 6

6 7

6 8

Typical sample size:1 mg Carbon

5x1019 12C atoms

6x1017 13C atoms

6x107 14C atoms

1 14C decay/hour (liquid scintillation counting)

106 14C atoms/hour (atom counting with AMS)

Determination of the 14C content in carbon( 14C/12C = 1.2x10-12 )

Accelerator Mass Spectrometry (AMS) for “all“ isotopes: 10Be, 14C, 26Al, 36Cl, 41Ca, 55Fe, 129I,182Hf, 210Pb, 210Bi, 236U, 293-244Pu, SHE, (H2)

–, (43Ca19F4)– –, PIXE-ART, Nucl. reactions: 6,7Li

Negative-Ion Sources

Negative-Ion MassSpectro-meter(keV)

Positive-Ion MassSpectro-Meter(MeV)

Stripping and Molecule Dissociation

Detector area

1996: 1st operation2001: 1st upgrade2007: 2nd upgrade

Essentially all AMS facilities use negative ions

Isotope Abundance

12C– 98.9 %

13C– 1.1 %14C– 0.000 000 000 1 %12CH2

– ~0.1%13CH– ~0.001%14N– 0 !

Kavalierstrakt

Paul Damon, Univ. of Arizona Pioneer in 14C dating

V E R AVienna Environmental

Research Accelerator

wallsremoved

entrance foraccelerator

Positioning of the 3-MV Pelletron tandem accelerator from NEC in the“Kavalierstrakt“, Währingerstr. 17, A-1090 Wien (1995)

Column structure of the 3-MV tandem accelerator of VERA

Peter Steier

Robin Golser

Eva Maria Wild

Alfred Priller

Vienna EnvironmentalResearch Accelerator

(3-Million Volt Tandem)

KAVALIERSTRAKT

First Floor

Sample Preparation

Sample preparation for 14C measurements

1. Pretreatment

ultrasinic bath (removal of adherent particles)

ABA (acid-base-acid; removal of carbonates, humic acid)

“crude gelatine“ (collagen extraction from bone)

2. Combustion to CO2

sample (~10 mg) + CuO →→→→ (900 °C) →→→→ CO2 + H2O, N2,...

3. Catalytic “graphitization to elemental carbon

CO2 + 2H2 →→→→ (Fe, 580 °C) →→→→ C + H2O

4. Target pressing

iron-carbon mixture (~1 mg) is pressed into aluminum

target holders of the Cs-beam sputter ion source

Ion source

(MC-SNICS, NEC)

The Cesium-Beam Sputter Source for Negative Ionsas developed by the late Roy Middleton in the 1980s

at the University of Pennsylvania

Cesium Vapor

Acceleration Region

Carbon Target

50 µA 12C‾Cs+

400 14C‾/s

hot surface~ 1000 °C

The World of VERA

Staff of VERA

Eva Maria WildVice Head of Isotope Research

Group, Head of 14C dating, sample

preparation and stable isotope lab

Research interests

Archaeology (14C), paleodiet (δ13C, δ 15N), paleoclimate (10Be, 26Al)

Robin GolserHead of Isotope Research

Group

Research interests

Atomic physics (exotic ions),

ion beam analysis (PIXE

and PIGE)

Alfred PrillerTechnical Head of VERA

Research interests:

Accelerator development

(ion source, injector),

loess and paleoclimate

(10Be)

Peter SteierHead of VERA Operation

Research interests:

Glacier dating (14C),

DNA dating (14C),

environmental physics

(36Cl, 236U, 244Pu)

Anton Wallner

Research interest

Nuclear physics (fusion: 26Al, 53Mn), nuclear astrophysics

(supernova remnants: 244Pu;

stellar nucleosynthesis: 10Be, 14C, 26Al, 36Cl, 41Ca, 55Fe,

210mBi, 236U)

Oliver Forstner

Research interests

Instrumentation, detector

development, laser

interaction with negative

ions (HfFn–)

Radiocarbon dating of the Santorini eruption

Black Sea

Mediterranean Sea CreteCyprus

Nile Delta

Anatolia

Santorini

Tell el-Daba

Palestine

Cairo

Luxor

(West Thebes)

Greece

Santorini Eruption Radiocarbon Dated to 1627-1600 BC

W. L. Friedrich, T. Pfeiffer

Department of Earth Sciences, University of Aarhus, Denmark

B. Kromer, S. Talamo

Heidelberger Akademie der Wissenschaften und Institut für Umweltphysik

Universität Heidelberg, Germany

M. Friedrich

Institut für Botanik, Universität Hohenheim, Germany

J. Heinemeier

Accelerator Mass Spectrometry 14C Dating Centre

Department of Physics and Astronomy, University of Aarhus, Denmark

Science 312 (28 April 2006) 548

TreeTree

Minoan Pumice

Tom Pfeiffer

Olive branch in pumice

Pumice section on Santorini

(Thera) showing the location of

the olive tree branch (lowermost

hole) and the presumed position

of the tree (ghosted)

Walter Friedrich

Olive tree branch

X-ray tomography, cross section

of the olive tree branch

X-rayimage

1750 1700 1650 1600 1550 15003150

3200

3250

3300

3350

3400

3450

3500

Outermost ring set to 1525

Santorini Olive

14C

age B

P

cal BC

-150 -100 -50 0 50

3150

3200

3250

3300

3350

3400

3450

3500

Santorini

German oak Heidelberg

Age of the outermosttree ring:

1613 ± 13 yr BC

Chronology for the Aegean Late Bronze Age

1700 – 1400 BC

S. W. Manning

Department of Classics, Cornell University, Ithaca, NY, USA and

Department of Archaeology, School of Human and Environmental Sciences

University of Reading, UK

C. Bronk Ramsey, T. Higham

Oxford Radiocarbon Accelerator Unit, Research Laboratory for Archaeology

and the History of Art, Oxford University, UK

W. Kutschera, P. Steier, E. M. WildVienna Environmental Research Accelerator (VERA) Laboratory

Institut für Isotopenforschung und Kernphysik, Universität Wien, Austria

B. Kromer

Heidelberger Akademie der Wissenschaften und Institut für Umweltphysik

Universität Heidelberg, Germany

Science 312 (28 April 2006) 565-569

127 14C dates from these sites were measured and analysed with the Bayesian method

Schematic representation of the Aegean early Late Bronze Age

archaeological chronology derived from 127 high-precision 14C measurements

Average of 28 short-livedsamples from the TheraVolcanic Destruction Layer(VDL)

Acrotiri (1660-1612 BC)

Average of 28 short-livedsamples from the TheraVolcanic Destruction Layer(VDL)

Acrotiri (1660-1612 BC) Olive tree (1627-1600 BC)

Tell el-Daba in the Nile Delta

Tell el-Daba

Tell el-Daba excavation area

Manfred Bietak“King“ of

Tell el-Daba

1868 BC 1540 BC

(2006): 5 1 3 2 4 2 2 1 4 6 6 1 2 1

Stele

(Sesostris III)

Destruction layer

(Ahmose I)

TheraPumice

White slip wareand Minoan-style paintingThera

eruption

S. W. Manning et al., C14 – VDL date, Science 312 (2006) 565W. L. Friedrich et al., C14 - Olive tree, Science 312 (2006) 548

Middle Kingdom Second IntermediatePperiodHyksos

Samples per phase: 5 1 3 2 4 2 2 1 4 6 6 1 2 1

Short-lived plant material (seeds) was selected for 14C measurements

Middle Kingdom Second Intermediate PeriodHyksos

Comparison of 14C dates (calibrated 2-sigma ranges) with the historicalchronology of Egypt linked through the stratigraphy of Tell el-Daba phases

Middle Kingdom Second intermediate periodHyksos

Comparison of 14C dates (calibrated 2-sigma ranges) including 5 splits of samples measured at the Oxford AMS Lab with the historical chronology of

Egypt linked through the stratigraphy of Tell el-Daba phases

Middle Kingdom Second Intermediate PeriodHyksos

Comparison of 14C dates (2-sigma ranges after Bayesian sequencing)with the historical chronology of Egypt linked through

the stratigraphy of Tell el-Daba phases

Middle Kingdom Second Intermediate PeriodHyksos

Comparison of 14C dates (2-sigma ranges after Bayesian sequencing)with the historical chronology of Egypt linked through

the stratigraphy of Tell el-Daba phases

~120 year shift

Middle Kingdom Second Intermediate PeriodHyksos

Chronology of Dynastic Egypt and the Santorini eruptionFrom: Hendrik J. Bruins, Science 328, 1489, 18-June-2010

“It is better to be roughly right

than precisely wrong.“

- Einstein