Radiocarbon dating. Elisabetta Boaretto

Transcription

1 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 Kutschera Vienna Environmental Research Accelerator (VERA) Laboratory Faculty of Physics Isotope Research University of Vienna Synchronizing Clocks at Armageddon Workshop on Archaeological Dating Megiddo, Israel, June 2010

2 General Introduction to Radiocarbon

3 Standard Radiocarbon Dating 14 C t = 14 C O e -λt t = 1/λ x ln( 14 C O / 14 C t ) t = t 1 /2 /ln2 x ln( 14 C O / 14 C t ) Conditions: 14 C O must be known for all times. Because material of known age (tree rings) is available back to about 12,500 years B.P., 14 C O 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) ] t 1 /2 need not to be known accurately, because the 14 C determination the uncalibrated, so-called radiocarbon age is performed with exactly the same procedure in unknown samples as in the treering samples. The latter delivers the translation of the uncalibrated radiocarbon age into a calendar date.

4 Absolute Radiocarbon Dating 14 C t 14 N* + e - + ν e Total energy release: 156 kev Maximum recoil energy of 14 N*: 7.3 ev 14 C t = 14 C O e -λt = ( 14 C t + 14 N* ) e -λt t = 1/λ x ln( N*/ 14 C t ) t = t 1/2 /ln2 x ln( N*/ 14 Ct) Conditions: 14 C t and 14 N* must be measured t 1/2 must be accurately known 14 C O need not to be known

5 Change of chemical compound by in-situ decay of 14 C 12 C 12 C 14 C 12 C 12 C 12 C 12 C 12 C 14 N* 12 C 12 C 12 C Benzene Pyridine Reference: An attempt at absolute 14 C dating, Jacob Szabo and Israel Carmi (Weizmann Institute), Dror Segal and Eugenia Mintz (Israel Antiquities Authority), Radiocarbon 40/1 (1998)

6 O 3 + hν O 2 + O( 1 D) O( 1 D) + H 2 O 2OH OH /O 2 ~ 10-13!

7 Subfossil pine out of a gravel pit near Tapfheim, Danube river, grown 11,200 years before present (BP). (B. Kromer, University of Heidelberg) Reference value: 14 C/ 12 C = 1.2x ,000 10, Years before present

8 14 C Bomb Peak Natural 14 C variations Variation of the 14 C content in atmospheric CO 2 during the last 4000 Years

9 NTBT C decay (t 1/2 = 5740 a) Natural 14 C level Long-term observations of 14 C in atmospheric CO 2 in the northern and in the southern hemisphere Levin and Hesshaimer, Univ. Heidelberg, Radiocarbon 42/1 (2000) 69

10 Bow 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

11 14 C dating of bone and tissue from the Iceman Ötzi at the AMS labs of Oxford and Zürich in 1992 Uncalibrated (radiocarbon) age: 4550 ± 19 yr BP (before present) Calibrated age range: 5300 to 5050 BP

12 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

13 Sampled areas for 14 C measurements at VERA

14 Radiocarbon ages determined for the human remains from the Mladeč site in Moravia (Czech Republic) Lab Number Sample Name Sample material 14 C-age (years BP) VERA-2736 Mladeč 25c Ulna 26,330 ± 170 VERA-3073 Mladeč 1 Right molar M2 31,190 ± 400 distal half of the crown VERA-3074 Mladeč 2 Left molar M3 31,320 ± 400 distal half of the crown VERA-3075 Mladeč 8 Left molar M2 30,680 ± 380 mesial-buccal root VERA-3076A Mladeč 9a Right maxillary canine, Lingual half 31,500 ± 410 of the root (white-coloured collagen) VERA-3076B Mladeč 9a Right maxillary canine, Lingual half 27,370 ± 230 of the root (brown-coulored collagen)

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

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18 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)

19 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.

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

21 Investigating the likelihood of a reservoir offset in the radiocarbon 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)

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

23 14 C AMS measurements at Oxford of 66 shortlived plants grown in Egypt between 1702 and 1881 resulted in an offset of 19 ± 5 years. Investigating the likelyhood of a reservoir offset in the radiocarbon record for ancient Egypt, Dee et al., J. Archaeol. Sci 37 (2009)

24 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)

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26 A brief introduction to VERA, the Vienna Environmental Research Accelerator

27 VERA WIEN 0.5 km 1.5 km

28 VERA 1993 Währinger Straße 17

29 VERA 1993 Wolfgang Amadeus Mozart composed here Cosi fan tutte in 1790

30 VERA 1993 Wolfgang Amadeus Mozart composed here Cosi fan tutte in 1790 Ludwig van Beethoven died here in 1827

31 800 m to birth place of Franz Schubert, 1799 VERA 1993 Wolfgang Amadeus Mozart composed here Cosi fan tutte in 1790 Ludwig van Beethoven died here in 1827

32 800 m to birth place of Franz Schubert, 1799 VERA 1993 Wolfgang Amadeus Mozart composed here Cosi fan tutte in m down this road, Sigmund Freud lived from 1891 to 1938 Ludwig van Beethoven died here in 1827

33 Victor Hess discovered Cosmic radiation in m to birth place of Franz Schubert, 1799 VERA 1993 Wolfgang Amadeus Mozart composed here Cosi fan tutte in m down this road, Sigmund Freud lived from 1891 to 1938 Ludwig van Beethoven died here in 1827

34 Primary cosmic ray (proton) Victor Hess Baloon flights in 1912 up to 5000 m Victor F. Hess shared the 1936 Nobel Prize in Physics (for the discovery of cosmic rays) with Carl D. Anderson (for the discovery of the positron)

35 Willard F. Libby ( ) 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

36 14 C o 14 C t = 14 C o e -λt 12 April 2007 Age determination by radiocarbon content: checks with samples of known age James R. Arnold and Willard F. Libby, Science 110 (1949)

37 Isotope abundances of some light elements Hydrogen 1 H % 2 H(D) % Carbon 12 C % C % C % (t 1/2 = a) 6 8 Nitrogen 14 N % 15 N % Oxygen 16 O % 17 O % 18 O %

38 Determination of the 14 C content in carbon ( 14 C/ 12 C = 1.2x10-12 ) Typical sample size:1 mg Carbon 5x x x C atoms 13 C atoms 14 C atoms 1 14 C decay/hour (liquid scintillation counting) C atoms/hour (atom counting with AMS)

39 Accelerator Mass Spectrometry (AMS) for all isotopes: 10 Be, 14 C, 26 Al, 36 Cl, 41 Ca, 55 Fe, 129 I, 182 Hf, 210 Pb, 210 Bi, 236 U, Pu, SHE, (H 2 ), ( 43 Ca 19 F 4 ), PIXE-ART, Nucl. reactions: 6,7 Li Negative-Ion Sources Negative- Ion Mass Spectrometer (kev) Stripping and Molecule Dissociation 1996: 1 st operation 2001: 1 st upgrade 2007: 2 nd upgrade Positive- Ion Mass Spectro- Meter (MeV) Detector area

40 Essentially all AMS facilities use negative ions Isotope Abundance 12 C 98.9 % 13 C 1.1 % 14 C % 12 CH 2 ~0.1% 13 CH ~0.001% 14 N 0!

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

42 V E R A Vienna Environmental Research Accelerator walls removed entrance for accelerator

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

44 Column structure of the 3-MV tandem accelerator of VERA Eva Maria Wild Alfred Priller Robin Golser Peter Steier

45 Vienna Environmental Research Accelerator (3-Million Volt Tandem)

46 Sample Preparation KAVALIERSTRAKT First Floor

47 Sample preparation for 14 C 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 CO 2 sample (~10 mg) + CuO (900 C) CO 2 + H 2 O, N 2, Catalytic graphitization to elemental carbon CO 2 + 2H 2 (Fe, 580 C) C + H 2 O 4. Target pressing iron-carbon mixture (~1 mg) is pressed into aluminum target holders of the Cs-beam sputter ion source

48 Ion source (MC-SNICS, NEC)

49 The Cesium-Beam Sputter Source for Negative Ions as developed by the late Roy Middleton in the 1980s at the University of Pennsylvania Carbon Target Acceleration Region Cs + 50 µa 12 C C /s Cesium Vapor hot surface ~ 1000 C

50 The World of VERA

51 Staff of VERA Robin Golser Head of Isotope Research Group Research interests Atomic physics (exotic ions), ion beam analysis (PIXE and PIGE) Eva Maria Wild Vice Head of Isotope Research Group, Head of 14 C dating, sample preparation and stable isotope lab Research interests Archaeology ( 14 C), paleodiet (δ 13 C, δ 15 N), paleoclimate ( 10 Be, 26 Al) Alfred Priller Technical Head of VERA Research interests: Accelerator development (ion source, injector), loess and paleoclimate ( 10 Be) Anton Wallner Research interest Nuclear physics (fusion: 26 Al, 53 Mn), nuclear astrophysics (supernova remnants: 244 Pu; stellar nucleosynthesis: 10 Be, 14 C, 26 Al, 36 Cl, 41 Ca, 55 Fe, Peter Steier Head of VERA Operation Research interests: Glacier dating ( 14 C), DNA dating ( 14 C), environmental physics ( 36 Cl, 236 U, 244 Pu) Oliver Forstner Research interests Instrumentation, detector development, laser interaction with negative ions (HfF n ) 210m Bi, 236 U)

52 Radiocarbon dating of the Santorini eruption

53 Black Sea Greece Anatolia Mediterranean Sea Santorini Crete Cyprus Palestine Nile Delta Tell el-daba Cairo Luxor (West Thebes)

54 Santorini Eruption Radiocarbon Dated to 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 14 C Dating Centre Department of Physics and Astronomy, University of Aarhus, Denmark Science 312 (28 April 2006) 548

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56 Minoan Pumice Tom Pfeiffer

57 Olive branch in pumice

58 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

59 Olive tree branch

60 X-ray tomography, cross section of the olive tree branch X-ray image

61 Santorini Olive Santorini German oak Heidelberg C age BP Outermost ring set to cal BC

62 Age of the outermost tree ring: 1613 ± 13 yr BC

63 Chronology for the Aegean Late Bronze Age 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. Wild Vienna 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)

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

65 Schematic representation of the Aegean early Late Bronze Age archaeological chronology derived from 127 high-precision 14 C measurements

66 Average of 28 short-lived samples from the Thera Volcanic Destruction Layer (VDL) Acrotiri ( BC)

67 Average of 28 short-lived samples from the Thera Volcanic Destruction Layer (VDL) Acrotiri ( BC) Olive tree ( BC)

68 Tell el-daba in the Nile Delta

69 Tell el-daba

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72 Tell el-daba excavation area

73 Manfred Bietak King of Tell el-daba

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75 Stele (Sesostris III) Destruction layer (Ahmose I) 1868 BC 1540 BC (2006): Middle Kingdom Second IntermediatePperiod Hyksos Thera eruption S. W. Manning et al., C14 VDL date, Science 312 (2006) 565 W. L. Friedrich et al., C14 - Olive tree, Science 312 (2006) 548 White slip ware and Minoanstyle painting Thera Pumice

76 Short-lived plant material (seeds) was selected for 14 C measurements Samples per phase: Middle Kingdom Second Intermediate Period Hyksos

77 Middle Kingdom Second intermediate period Hyksos Comparison of 14 C dates (calibrated 2-sigma ranges) with the historical chronology of Egypt linked through the stratigraphy of Tell el-daba phases

78 Middle Kingdom Second Intermediate Period Hyksos Comparison of 14 C 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

79 Middle Kingdom Second Intermediate Period Hyksos Comparison of 14 C dates (2-sigma ranges after Bayesian sequencing) with the historical chronology of Egypt linked through the stratigraphy of Tell el-daba phases

80 ~120 year shift Middle Kingdom Second Intermediate Period Hyksos Comparison of 14 C dates (2-sigma ranges after Bayesian sequencing) with the historical chronology of Egypt linked through the stratigraphy of Tell el-daba phases

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

82 It is better to be roughly right than precisely wrong. - Einstein