Stéphanie Leroy

Relevance of NH4F in acid digestion before ICP-MS analysis.

In order to implement a simpler, less expensive and more safe sample dissolution procedure, we have substituted the HF-HClO(4) mixture by NH(4)F. By testing three certified reference materials, lichen 336, basalt BE-N, soil 7, it was found that the three-reagents digestion without HF and HClO(4) (HNO(3)+H(2)O(2)+NH(4)F was used) was very effective for the pretreatment of ICP-MS measurement. The comparison was based on the measurement results and their uncertainties. All are reference material for amount contents of different trace elements. The accuracy and precision of the developed method were tested by replicate analyses of reference samples of established element contents. The accuracy of the data as well as detection limits (LODs) vary among elements but are usually very good (accuracy better than 8%, LODs usually below 1 microg/g in solids). ICP-MS capabilities enable us to determine routinely 13 and 16 minor and trace elements in basalt and soil.

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.

Smelting in the Shadow of the Iron Mountain: Preliminary Field Investigation of the Industrial Landscape around Phnom Dek, Cambodia (Ninth to Twentieth Centuries a.d .)

abstract: The high-grade mineral ores of the Phnom Dek region in central Cambodia have long been suspected of playing a major role in the rise of Angkor, the largest medieval polity in mainland Southeast Asia. This article presents the first comprehensive study by the Industries of Angkor Project (INDAP) to document the extent of industrial activity in this region and test this important relationship. Using a combination of intensive field survey, surface collection, and archaeometallurgical analysis, we evaluate the temporal and spatial patterning of iron production and the heterogeneity of smelting systems. The identification of at least three different smelting traditions has a significant impact on the current view that twentieth-century Kuay smelting practices extend deep into Cambodia’s history, and their relationship with Angkor in particular. More broadly, the survey demonstrates the importance of Phnom Dek as a major production zone on par with more well-known examples in Roman Europe and Africa.

Characterization of Slag Inclusions in Iron Objects

Tracing the origins of iron artifacts generates great interest in iron metallurgy. Chemical analysis of non-metallic slag inclusion (SI) entrapped in iron produced in bloomery furnaces is an efficient mean for provenance studies as, within their composition, SI do not only carry the conditions of production but also the chemical signature of the iron ore initially used. The analytical protocol is a three stage process: (a) metallographic identification and selection of SI, (b) characterization of their main component using SEM-EDX, (c) traces element determination using LA-ICP-MS. LA-ICP-MS analysis allows to quantify up to 39 trace elements in the fayalitic-rich matrix of SI with detection limits at the ppm level. Compositional ratios are then compared with one another and to the chemical signature of previously analysed regions of production. The methodology was applied on iron armatures from the cathedral of Bourges to study their fabrication, their installation in the building and their provenance. Results obtained allow a better understanding of the role of these armatures and the supply of this construction site.

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.