Emmanuelle Delqué-Količ

Radiocarbon intercomparison program for Chauvet Cave

We present the first results of an accelerator mass spectrometry (AMS) radiocarbon intercomparison program on 3 different charcoal samples collected in one of the hearths of the Megaceros gallery of Chauvet Cave (Ardche, France). This cave, rich in parietal decoration, is important for the study of the appearance and evolution of prehistoric art because certain drawings have been 14C dated to the Aurignacian period at the beginning of the Upper Paleolithic. The new dates indicate an age of about 32,000 BP, which is consistent with this attribution and in agreement with the results from the same sector of the cave measured previously at the Laboratoire des Sciences du Climat et de lEnvironnement (LSCE). Six laboratories were involved in the intercomparison. Samples were measured in 4 AMS facilities: Center for Isotope Research, Groningen University, the Netherlands; the Oxford Radiocarbon Accelerator Unit, UK; the Centre de datation par le carbone 14, Univ. Claude Bernard Lyon 1, France (measured by AMS facilities of Poznan University, Poland); and the LSCE, UMR CEACNRS-UVSQ, France (measured by the Leibniz-Labor of Christian-Albrechts-Universitt Kiel, Germany).

Can we Use Calcined Bones for 14C Dating the Paleolithic

This work aims to test the reliability of calcined bones for radiocarbon dating of the Paleolithic. Fifty-five calcined bone samples coming from Aurignacian and Gravettian layers at Abri Pataud (Dordogne, France) were selected based on their macroscopic features. For each sample, the heating state was estimated on the basis of bone crystallinity (splitting factor [SF] using FTIR) and δ 13 C value. Twenty-seven bone samples (3 unburnt and 24 calcined) from 5 different levels were prepared for 14 C dating. The majority (15/24) of the calcined samples had to undergo a sulfix treatment prior to graphitization, probably due to the presence of cyanamide ion in these samples. The comparison between our results and recently published dates on bone collagen for the same levels shows that unburned bone apatite is systematically too young, while a third of the calcined bones fall within or very near the range of expected age. No clear correlation was found between 14 C age offset and δ 13 C value or SF. Most of the sulfixed samples (14/16) yielded ages that were too young, while almost all of the non-sulfixed samples (8/9) gave ages similar or 2 gas from well-calcined Paleolithic bones can provide reliable 14 C ages.

First Direct Dating for the Construction and Modification of the Baphuon Temple Mountain in Angkor, Cambodia.

Architecture represents key evidence of dynastic practice and change in the archaeological world. Chronologies for many important buildings and sequences, including the iconic temples of medieval Angkor in Cambodia, are based solely on indirect associations from inscriptions and architectural styles. The Baphuon temple, one of the last major buildings in Angkor without textual or scientifically-derived chronological evidence, is crucial both for the context and date of its construction and the period when its western façade was modified into a unique, gigantic Reclining Buddha. Its construction was part of a major dynastic change and florescence of the Hindu-Mahayana Buddhist state and the modification is the key evidence of Theravada Buddhist power after Angkors decline in the 15th century. Using a newly-developed approach based on AMS radiocarbon dating to directly date four iron crampons integrated into the structure we present the first direct evidence for the history of the Baphuon. Comprehensive study of ferrous elements shows that both construction and modification were critically earlier than expected. The Baphuon can now be considered as the major temple associated with the imperial reformations and territorial consolidation of Suryavarman I (1010–1050 AD) for whom no previous building to legitimize his reign could be identified. The Theravada Buddhist modification is a hundred years prior to the conventional 16th century estimation and is not associated with renewed use of Angkor. Instead it relates to the enigmatic Ayutthayan occupation of Angkor in the 1430s and 40s during a major period of climatic instability. Accurately dating iron with relatively low carbon content is a decisive step to test long-standing assumptions about architectural histories and political processes for states that incorporated iron into buildings (e.g., Ancient Greece, medieval India). Furthermore, this new approach has the potential to revise chronologies related to iron consumption practices since the origins of ferrous metallurgy three millennia ago.

Advances in Handling Small Radiocarbon Samples at the Laboratoire de Mesure du Carbone 14 in Saclay, France

The Artemis accelerator mass spectrometry (AMS) facility, installed in 2003 in Saclay, France, is devoted to radiocarbon measurements. Samples are submitted by scientists in the fields of Quaternary geology, environmental sciences, and archaeology. The entire preparation process, originally optimized for samples with about 1 mg of carbon, has been tested in recent years for samples with a lower carbon content. In particular, we prepared and measured carbonate and organic background and reference samples ranging in mass from 0.01 to 1 mg C. These tests helped define our protocol’s practical limits and determine necessary improvements. Furthermore, our experiments demonstrated that satisfactory graphitization yields (80% and higher) and low background values can be obtained with samples down to 0.2 mg of carbon. For handling smaller samples, we developed a specific process. We tested smaller reactors (5 mL in volume) and adapted the reduction parameters (H2 pressure and temperature) accordingly. We also tested the effect of a chemical water trap on graphitization yields and 14C results. This paper presents in detail the aforementioned developments and reports the 14C results obtained for background and standard small samples prepared with the modified reactors.

Iron Bar Trade between the Mediterranean and Gaul in the Roman Period: 14C Dating of Products from Shipwrecks Discovered off the Coast of Saintes-Maries-de-la-Mer (Bouches-du-Rhône, France)

Since the 90s, the large number of iron-laden wrecked ships discovered off Saintes-Maries-de-la-Mer (south of France), enriches our knowledge of both maritime trade in the Mediterranean and the ferrous bars used during Antiquity. This exceptional corpus has spawned numerous studies in the fields of archaeology, history and archaeometallurgy (Pages et al. 2011), but, despite a relatively well-documented context, the chronology of wrecks is still to be clarified. So far, the chronology of the corpus was mainly supported by the archaeological remains found in the cargo of the wrecks, bringing a chronological range from the first century BC to the first century AD. However, the 14C dating of an iron bar from Saintes-Maries-de-la-Mer, older of more than a century from the expected chronological range, has revived discussions about the chronology of all the wrecks. Thanks to the development of a new protocol for dating ferrous alloys, based on an extensive study of the ferrous material (Leroy et al. 2015a), 34 samples of iron extracted from 13 ferrous bars constituting the cargo of 7 ships could be 14C dated. The radiocarbon results and the archaeological and historical data were implemented in the Bayesian tool Oxcal to build a chronological framework for the antique shipwrecks of Saintes-Maries-de-la-Mer. It appears that all these ships could belong to a larger phase than the one deduced from archaeological remains alone. In consequence, this study helps to support a new vision of the trade between the north-eastern Mediterranean and Western Europe.

The ties that bind: archaeometallurgical typology of architectural crampons as a method for reconstructing the iron economy of Angkor, Cambodia (tenth to thirteenth c.)

The dynamic technological characteristics and diverse cultural potential of iron make it one of the most influential materials for facilitating cultural transformation. Reconstructing how iron was managed is an important way to understand political and socioeconomic issues in pre-modern state-level societies. In contrast to studies of smelting sites, the study of iron objects allows us to evaluate trends of production in relation to practice of consumption. By investigating a given class of iron objects, it is possible to document shifts in technical processes, cultural choices, and social organisation that are representative of a state or polities broader iron economy. This study outlines the use of comprehensive archaeometallurgical typology, a new approach combining technological, chronological, and “sourcing” analyses of iron architectural crampons from the Khmer capital of Angkor (ninth to fifteenth c. CE) in Cambodia. Our methodology was implemented on 69 iron crampons from three masonry complexes (the Royal Palace, Baphuon, and Preah Khan) spanning the tenth to thirteenth centuries. Compiling a vast and statistically significant data set enables us to identify diachronic changes of production and manufacturing patterns that seem to be linked to key periods of expansion of the Khmer Empire. These patterns represent the first phase in reconstructing the iron economy of the most influential polities in mainland Southeast Asia.

Development of a Line for Dissolved Inorganic Carbon Extraction at LMC14 Artemis Laboratory in Saclay, France

We present here the new line installed at the LMC14 laboratory (Saclay, France) for dissolved inorganic carbon (DIC) extraction from marine and freshwater samples. The operating system and extraction process are described. The efficiency of the line design was checked, and the background (0.42 ± 0.11 pMC) and the reproducibility on artificial samples obtained by dissolution of IAEA-C1, IAEA-C2, and commercial bicarbonate in water were evaluated. An intercomparison with an independent lab (IDES) was also carried out on a natural sample. The line processes 3 samples a day under a helium flow and is able to run samples up to 40,000 ka.