The Roman amphitheatre in Mérida, Spain ˗Augustan or Flavian? Radiocarbon dating results on mortar carbonate

Alf Lindroos; Jan Heinemeier; Åsa Ringbom; Thomas Schrøder Daugbjerg; Irka Hajdas

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The Roman amphitheatre in Mérida, Spain ˗Augustan or Flavian? Radiocarbon dating results on mortar carbonate

Alf Lindroos

Jan Heinemeier

Åsa Ringbom

Thomas Schrøder Daugbjerg

oraz

Irka Hajdas

| 31 gru 2020

Geochronometria

Tom 47 (2020): Zeszyt 1 (January 2020)

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Article Category: CONFERENCE PROCEEDINGS OF THE 13TH INTERNATIONAL CONFERENCE “METHODS OF ABSOLUTE CHRONOLOGY” JUNE 5-7TH, 2019, TARNOWSKIE GORY, POLAND

Data publikacji: 31 gru 2020

Zakres stron: 187 - 195

Otrzymano: 29 maj 2020

Przyjęty: 30 wrz 2020

DOI: https://doi.org/10.2478/geochr-2020-0028

Słowa kluczowe
Mortar dating, hydraulic mortar, sequential dissolution, CO2 fractions

© 2020 A. Lindroos., published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

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.

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.

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

$14C profiles from three different sample preparations of sample Mérida 001: Open circles are from the first dating attempt in 2001. Open boxes are from supplementary measurements later the same year and black diamonds from re-dating 2018. The grey bars along the abscissa denote the size of each CO2 fraction relative to the total CO2 yield. In all the following 14C profile plots the size of the CO2 fractions will be presented the same way without specific mention.$

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.

14C profiles of sample Mérida 002. Open circles present dating in 2001 and black boxes dating in 2018.

Fig 6

$14C profiles of sample Mérida 003. Open circles denote dating in 2001 and open boxes a profile in six CO2 fractions dated later the same year. Black diamonds represent re-dating in 2018. For this sample we used the same powder that had been in a non-airtight container for 17 years. The data point with low F value representing initially effervesced CO2 was measured to ensure that the sample powder had not captured modern CO2 and grown new calcite on the grains.$

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).

14C profiles from sample Mérida 004. Open circles, dating 2001. Black boxes, dating 2018.

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.

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	Al₂O₃	Ba	CaO	FeO	K₂O	MgO	Mn	Na₂O	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	(%)	(%)	H₃PO₄ (%)	(%)	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	¹⁴C	±	δ¹³C	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

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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

Data publikacji: 31 gru 2020

Zakres stron: 187 - 195

Otrzymano: 29 maj 2020

Przyjęty: 30 wrz 2020

DOI: https://doi.org/10.2478/geochr-2020-0028

Słowa kluczowe
Mortar dating, hydraulic mortar, sequential dissolution, CO2 fractions

© 2020 A. Lindroos., published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

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