The Roman amphitheatre in Mérida, Spain ˗Augustan or Flavian? Radiocarbon dating results on mortar carbonate Article Category: CONFERENCE PROCEEDINGS OF THE 13TH INTERNATIONAL CONFERENCE “METHODS OF ABSOLUTE CHRONOLOGY” JUNE 5-7TH, 2019, TARNOWSKIE GORY, POLAND Publié en ligne: 31 déc. 2020 Pages: 187 - 195 Reçu: 29 mai 2020 Accepté: 30 sept. 2020 © 2020 A. Lindroos., published by Sciendo This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.
Fig 1 Sample positions 1-4 in the amphitheatre. Sampling: Upper left, Mérida 001; Upper right, Mérida 002; Lower left, Mérida 003; Lower right, Mérida 004. See details in the text. Fig 2 Thin section images. Upper left: 100μm section of sample Mérida 001 in transmitted light. Transparent minerals are mostly quartz. CL images: Upper right, cut and polished surface of a piece from sample Mérida 003 showing distribution between calcite (red) and other binder minerals (black). Mid left, the dated 46-75μm grainsize fraction of sample Mérida 001; Mid right, Mérida 003 ditto. Lower left, Mérida 004 ditto. Images from sample Mérida 002 are omitted because it turned out to be younger and less relevant. Red minerals are calcite and dark red ones have a dolomitic component while more orange ones are purer. Blue and turquoise are quartz and dull green are feldspar. The green dust-like powder in the slice is secondary aragonite from grinding. There is also a void filled with an extremely luminescent mineral in lilac, which we have not tried to identify. Fig 3 TGA profiles of the four samples from Mérida. The profiles are similar, but the most hydraulic samples Mérida 003 and 004 have lower CO2 yields and consequently more residue. Fig 4 14C profiles from three different sample preparations of sample Mérida 001: Open circles are from the first dating attempt in 2001. Open boxes are from supplementary measurements later the same year and black diamonds from re-dating 2018. The grey bars along the abscissa denote the size of each CO2 fraction relative to the total CO2 yield. In all the following 14C profile plots the size of the CO2 fractions will be presented the same way without specific mention. Fig 5 14C profiles of sample Mérida 002. Open circles present dating in 2001 and black boxes dating in 2018. Fig 6 14C profiles of sample Mérida 003. Open circles denote dating in 2001 and open boxes a profile in six CO2 fractions dated later the same year. Black diamonds represent re-dating in 2018. For this sample we used the same powder that had been in a non-airtight container for 17 years. The data point with low F value representing initially effervesced CO2 was measured to ensure that the sample powder had not captured modern CO2 and grown new calcite on the grains. Fig 7 14C profile from sample Mérida 003 after heating the sample to 620˚C. Some of the young carbonates have been lost and the profile now increases more rapidly in the beginning compared with the profile from the non-heated original sample powder (Fig. 6). Fig 8 14C profiles from sample Mérida 004. Open circles, dating 2001. Black boxes, dating 2018. Fig 9 14C data from 2018. Data points for each sample are connected with lines for clarity. Samples Mérida 001, 003 and 004 yield similar 14C ages after about 20% dissolution (F>0.2) whereas sample Mérida 002 appears younger in all fractions. Fig 10 Combined calibration of 5 CO2 fractions with similar ages. The calibration includes the 3 last fractions from sample Mérida 001 and the two last ones from Merida 004 in Fig 9. ICP-OES analyses of the soluble phase of the samples when dissolved for 1h in 1M HCl at room T. For comparison, 3 samples from the Medieval Bishop Masonas Hospital (Mérida 005, 006 and 007) and 3 samples from the Colosseum are included. Major elements are converted to oxides. Sample ID Al2 O3 Ba CaO FeO K2 O MgO Mn Na2 O SiO2 Sr Hydraulic % mg/kg % % % % mg/kg % % mg/kg index Mérida 001 0.08 70.8 30.2 0.21 <0.05 3.12 253 0.09 0.51 578 0,02 Mérida 002 0.08 61.9 27.3 0.21 <0.05 4.22 295 0.58 0.68 552 0,03 Mérida 003 0.11 60.7 17.9 0.13 <0.05 2.59 133 0.04 0.34 376 0,03 Merida 005 0.14 56.9 19.0 0.19 0.02 1.18 225 0.05 0.25 378 0,03 Mérida 006 1.69 169 15.3 0.25 0.09 0.71 73.3 0.02 0.36 51 0,17 Mérida 007 1.54 184 15.6 0.21 0.12 0.82 61.2 0.01 1.79 85 0.13 Colosseum001 5.61 519 15.8 0.54 2.04 0.28 312 1.49 2.65 490 0,55 Colosseum002 5.29 621 20.7 0.55 1.85 0.35 165 1.26 3.17 588 0,43 Colosseum003 8.01 1660 6.66 0.76 1.87 0.93 355 1.28 3.83 690 1,66
Numerical TGA data and the CO2 yield in H3PO4 hydrolysis for aliquots of the same sample material. For TGA about 10mg of the 46-75μm was heated and in the hydrolysis about 50mg was reacted with 85% H3PO4. The acid was taken from an ice bath but it reached room T before the reaction ceased after about 1h. Sample LOI 550 LOI 850 CO2 yield Residue LOI(850˚/550˚) ID (%) (%) H3 PO4 (%) (%) ratio Mérida 001 3.6 26 26 69 7.2 hydraulic Mérida 002 4.3 27 16 66 6.3 hydraulic Mérida 003 4.0 19 16 74 4.8 hydraulic Mérida 004 4.8 22 25 71 4.6 hydraulic Colosseum 003 2.7 7.6 3.7 81 2.8 hydraulic
j.geochr-2020-0028.tab.003.w2aab3b7d106b1b6b1ab2b2ab1Aa Site Sample nr Reaction Carbon Fraction 14 C± δ13 C Laboratory location run nr time yield size Age ‰ CO2 fraction nr (s) from t0 (tot %) (relative 1) (BP) VPDB nr Merida amphiteater Merida 001.1.1 67 7.4 0-0.198 1520 35 -13.0 AAR-6721.1 Main entance Merida 001.1.2 727 0.198-0.408 1600 40 -8.96 AAR-6721.2 Merida 001.2.1 600 6.9 0-0.325 1580 35 -10.1 AAR-6721.2.1 Merida 001.2.2 2820 0.325-0.646 1780 30 -8.40 AAR-6721.2.2 Merida 001.3.3 20-115 7.2 0.174-0.337 1865 21 -8.3 ETH-87848 Merida 001.3.4 540 0.337-0.604 1876 22 -10.2 ETH-87849 Merida 001.3.5 1380 0.604-0.820 1881 22 -10.9 ETH-87850 Merida 001.3.6 1980 0.820-0.919 1899 24 -9.3 ETH-89323 Main entrance Merida 002.1.1 43 8.0 0-0.187 1626 45 -13.7 AAR-6722.1 Merida 002.1.2 523 0.187-0.386 1790 40 -7.10 AAR-6722.2 Merida 002.2.2 30-120 4.4 0.273-0.470 1711 22 -7.0 ETH-87851 Merida 002.2.3 600 0.470-0.798 1781 21 -7.5 ETH-87852 Merida 002.2.4 1180 0.798-0.937 1825 25 -5.3 ETH-87863 Passage towards NE Merida 003.1.1 104 5.6 0-0.191 1530 40 -12.5 AAR-6723.1 Merida 003.1.2 884 0.191-0.394 1815 40 -9.9 AAR-6723.2 Merida 003.2.1 30 3.2 0-0.068 1335 40 -18.4 AAR-6723.2.1 Merida 003.2.2 510 0.068-0.365 1715 35 -9.82 AAR-6723.2.2 Merida 003.2.3 2490 0.365-0.631 1895 35 -9.66 AAR-6723.2.3 Merida 003.2.4 8790 0.631-0.850 1980 35 -10.4 AAR-6723.2.4 Merida 003.2.5 15990 0.850-0.943 1960 40 -11.8 AAR-6723.2.5 Merida 003.2.6 63000 0.943-1.00 2140 45 -10.2 AAR-6723.2.6 Merida 003.3.1 30 4.4 0-0.093 1383 25 -15.7 ETH-87864 Merida 003.2.8 530-1950 0.487-0.777 1852 21 -12.2 ETH-87853 “Roasting” Merida 003 Roa1.1 8 2.4 0-0.0174 hydrolysis after Merida 003 Roa1.2 25 0.0174-0.109 1539 34 -13 AAR-30431 heating to 620˚C Merida 003 Roa1.3 100 0.109-0.294 1821 29 -6 Merida 003 Roa1.4 580 0.294-0.582 1859 30 -8 Merida 003 Roa1.5 1320 0.582-0.800 1873 33 -10 Passage towards NE Merida 004.1.1 14 6.3 0-0.185 1320 50 17.7 AAR-6724.1 Merida 004.1.2 194 0.185-0.393 1795 40 -7.10 AAR-6724.2 Merida 004.2.2 6-19 6.8 0.068-0.128 1631 25 -14.1 ETH-87854 Merida 004.2.3 105 0.128-0.343 1827 23 -7.8 ETH-87855 Merida 004.2.4 580 0.343-0.658 1923 22 -11.6 ETH-87856 Merida 004.2.5 1440 0.658-0.870 1908 25 -10.6 ETH-89324