The Radiocarbon Dating Laboratory

Transcription

1 MINISTÈRE DE L'ÉDUCATION NATIONALE, DE L'ENSEIGNEMENT SUPÉRIEUR ET DE LA RECHERCHE Institut français d archéologie orientale The Radiocarbon Dating Laboratory Analysis Report IFAO _60 37, El-Sheikh Ali Youssef.street. BP Qasr el-ainy CAIRO EGYPT Tel: fax: C14@ifao.egnet.net

2 Analysis Report IFAO_0060 Sample identification : Site : Belad al-sham Client : Union Of Arab Archaeologists Reference of the sample given by the client : 4BFM Laboratory Data base Registration Nr. : 134 Sample Characteristics: Description Sample of bio-organic material found on a basalt stone surface Estimated Age by searcher : 1000 year Before Christ Pretreatment in the laboratory Physical treatment : Macro contaminants were removed from the sample by mechanical handpicking under optical microscope. The selected portion of the sample was treated with H 2 O 2 in order to chemically remove any possible source of surface contamination. Chemical treatment : The purified sample material was then converted to carbon dioxide by acid attack. The obtained carbon dioxide was converted at 550 C into graphite by using ultrahigh purity Hydrogen as reducing medium and 2 mg iron powder as catalyst. The sample yielded enough graphite to allow an accurate determination of the radiocarbon age by the accelerator mass spectrometer. The radiocarbon concentrations have been determined by CEDAD - AMS Radiocarbon Dating and IBA Facility_University of Lecce_Department of Engineering and Innovation in the accelerator mass spectrometer by comparing the 12 C, 13 C currents and the 14 C counts obtained from the samples with those obtained from standard materials supplied by IAEA (International Atomic Energy Agency) and NIST (National Institute of Standard and Technology). The conventional radiocarbon age was calculated with a δ 13 C correction based on the 13 C/ 12 C ratio measured directly with the accelerator. For the estimation of the measurement uncertainty (standard deviation) both the radioisotope counting statistics and the scattering of the data have been taken into account. The larger of the two is given as:

3 Results Analysis Report IFAO_0060 Conventional 14 C Age: ± 40 BP ( 1σ ). (One δ 13 C account measured: - 12,00 %±,0,1 vs PDB) (Compared by reference standard from National Institute of Standards and Technology ) Calibrated 14 C Date : 351 BC : 298 BC 23,9 % 140 BC : 112 BC 10,6 % ( 1σ ) 260 BC : 87 BC 61,9 % 295 BC : 276 BC 30,0 % ( 2σ ) (Calibration curve : IntCal 04 : Reimer.PJ and al IntCal 04 terrestrial radiocarbon age calibration,0-26 cal kyr BP. Radiocarbon. 46 ( 3 ) ). For the publication of the results, we recommend the following presentation resulting from the International Conventions: Dating by radiocarbon : Conventional age 14 C : ± 40 BP. (measured δ 13 C of 12,00 ± 0,1% vs PDB reference ). Calibrated 14 C Date : 351 BC : 298 BC 23,9 % 140 BC : 112 BC 10,6 % ( 1σ ) Calibration Curve: IntCal 04: Reimer PJ and Al IntCal 04 terrestrial radiocarbon age calibration, 0-26 cal kyr LP. Radiocarbon. 46 (3) ). Note The conventional 14 C age is expressed in years BP (before present, the present being by convention year 1950). It is calculated by using the period of Libby ( 5568 years ) and by measured δ 13 C of 12,00 % vs PDB). The uncertainty is given with a degree of confidence of 68,2 % of (either a sigma: 1σ ). The δ 14 C activity is calculated in percent compared to the activity of the International Standard, with an uncertainty of more or less ( 1 sigma ). The calibrated 14 C date given above is the interval within probability of the true value is 68,3% (1 sigma) It is expressed in years BC (Before Christ or before J-C.)or AD (Anno Domini or after J.-C.). The date is calculated using the calibration OxCal 4,0 calibration software (Bronk Ramsey C Radiocarbon calibration and analysis of stratigraphy : the OxCal program. Radiocarbon 37 (2) and Bronk Ramsey C Development of radiocarbon calibration program OxCal, Radiocarbon 43 (2A) )

4 Analysis Report IFAO_0060 Analysis Nature of the sample 14 C Conventional Age ( 1σ ) Calibrated Date IFAO _0060 Bio-organic material ± 40 BP Probability 68,2% (1σ) 351 BC : 298 BC 23,9 % 140 BC : 112 BC 10,6 % Probability 95,4% (2σ) 260 BC : 87 BC 61,9 % 295 BC : 276 BC 30,0 % Calibration Diagram

5 AnalysisReport IFAO_0060 4BFM Sampling spots on the stone by the IFAO Radiocarbon Dating Laboratory in Dubai -UAE the bright color is the bio-oganic materials