François-Xavier Le Bourdonnec

Eastern Anatolian obsidians at Çatalhöyük and the reconfiguration of regional interaction in the Early Ceramic Neolithic

A small group of exotic obsidian blades supplied from over 600km distant reached a particular area of the East Mound at Catalhoyuk in the Early Ceramic Neolithic (7000-6300 cal BC). The authors explore a variety of explanations and contexts, including changes in technology, agricultural expansion, gift exchange, bride-wealth and incomers from the east.

Obsidian exploitation and utilization during the Oldowan at Melka Kunture (Ethiopia)

The Oldowan assemblages of Melka Kunture represent the earliest known example of obsidian utilization. The proximity of primary and secondary sources of Balchit obsidian, a high quality raw material easily available in large quantities, is a unique situation among East African Oldowan sites. Obsidian represents a large component of the lithic assemblages at Melka Kunture, not only during the Oldowan but during the Acheulian times as well. Other volcanic rocks are incorporated into the technological system at Melka Kunture such as basalts, ignimbrites, trachytes and trachybasalts, which present completely different characteristics for knapping.

The extreme mobility of debris avalanches: A new model of transport mechanism

Large rockslide-debris avalanches, resulting from flank collapses that shape volcanoes and mountains on Earth and other object of the solar system, are rapid and dangerous gravity-driven granular flows that travel abnormal distances. During the last 50 years, numerous physical models have been put forward to explain their extreme mobility. The principal models are based on fluidization, lubrication, or dynamic disintegration. However, these processes remain poorly constrained. To identify precisely the transport mechanisms during debris avalanches, we examined morphometric (fractal dimension and circularity), grain size, and exoscopic characteristics of the various types of particles (clasts and matrix) from volcanic debris avalanche deposits of La Reunion Island (Indian Ocean). From these data we demonstrate for the first time that syn-transport dynamic disintegration continuously operates with the increasing runout distance from the source down to a grinding limit of 500 µm. Below this limit, the particle size reduction exclusively results from their attrition by frictional interactions. Consequently, the exceptional mobility of debris avalanches may be explained by the combined effect of elastic energy release during the dynamic disintegration of the larger clasts and frictional reduction within the matrix due to interactions between the finer particles.

Reconsidering prehistoric chert catchment sources: new data from the Central Pyrenees (Western Europe)

In the framework of a postdoctoral project to geochemically characterise Pyrenean cherts, a new marine chert outcrop in the Central Pyrenees has been defined. This new discovery, called the Buala outcrop, and its flysch chert type, provide new information about marine chert sources in the Pyrenean chain, leading us to reconsider prehistoric chert procurement in this area. Until now, two geological formations from the Central Pyrenees were considered as potential sources for a type of marine chert usually appearing in the Magdalenian record of several Pyrenean sites: Montgaillard flysch cherts and Montsaunès cherts. With both formations presenting similar characteristics, it was only through the use of geochemical methods that differences were recently established as reported by Sánchez de la Torre et al. (STAR 3:15–37, 2017b). This paper presents the new marine flysch chert outcrop of Buala. The visual, micropalaeontological and geochemical characterisation of this chert has permitted the definition of a new potential source for this marine chert type, which is common in several Palaeolithic sites in the Pyrenees, as Cova del Parco (Alòs de Balaguer, Spain), Forcas I Shelter (Graus, Spain), Montlleó open-air-site (Prats i Sansor, Spain), or Caune de Belvis (Belvis, France) (Sánchez de la Torre 2015). Geochemical characterisation of the three potential sources was carried out using energy-dispersive X-ray fluorescence (ED-XRF) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Results show that Buala flysch cherts are clearly different from the previously known chert types in terms of major, minor, and trace elements.

Sourcing obsidian: a new optimized LA-ICP-MS protocol

Abstract Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry [LA-ICP-MS] is one of the most successful analytical techniques used in archaeological sciences. Applied to the sourcing of lithic raw materials, it allows for fast and reliable analysis of large assemblages. However, the majority of published studies omit important analytical issues commonly encountered with laser ablation. This research presents a new advanced LA-ICP-MS protocol developed at Southern Cross GeoScience (SOLARIS laboratory, Southern Cross University, Australia), which optimizes the potential of this cutting-edge geochemical characterization technique for obsidian sourcing. This new protocol uses ablation lines with a reduced number of assayed elements (specific isotopes) to achieve higher sensitivity as well as increased precision and accuracy, in contrast to previous studies working with ablation points and an exhaustive list of measured isotopes. Applied to obsidian sources from the Western Mediterranean region, the Carpathian basin, and the Aegean, the results clearly differentiate between the main outcrops, thus demonstrating the efficiency of the new advanced LA-ICP-MS protocol in answering fundamental archaeological questions. Statement of significance Our new LA-ICP-MS protocol, specifically tailored for the geochemical sourcing of obsidian artefacts in the Western Mediterranean area, was developed at SOLARIS (Southern Cross GeoScience, Southern Cross University, Australia) with a top-of-the-range Agilent 7700x ICP-MS coupled to a an ESI NWR 213 Laser Ablation System. Taking into account the common analytical issues encountered with the LA-ICP-MS technique, we focused on two parameters: the use of ablation lines instead of ablation points, and the development of a reduced list of measured isotopes. The use of ablation lines aims to compensate for any sample heterogeneity, achieve a higher count rate as well as a better signal stability, and also reduce laser-induced elemental fractionation. The measured isotopes have been carefully selected amongst the most efficient to discriminate between the different obsidian sources. This shortened list of isotopes achieves precise and accurate measurements with a higher sensitivity, and with the use of ablation lines, contributes to enhancing the potential of this geochemical characterization technique for obsidian sourcing. Data availability The LA-ICP-MS results for the obsidian geological samples from the Mediterranean area are available as supplementary data. GRAPHICAL ABSTRACT

Towards High Resolution Ceramic Series for Production Site Studies: The Case of Loron Amphorae (Croatia, 1st?3rd C. A.D.)

BackgroundFrom the 1st to the 3rd centuries A.D., the territory of Istria (present-day Croatia) was a prominent area of olive oil production. Archaeologists have identified the so-called Dressel 6B amphora as the main container used in the transport and trade of this oil. So far archaeology and epigraphy have helped identify probable sources of production and two workshops in Istria, and have also allowed the reconstruction of main trade routes through the identification of stamped amphorae. However, much less is known about the organization of the production of these ceramic containers, which may have been conducted on an almost industrial scale. This preliminary study demonstrates how chemical analysis using energy-dispersive X-ray fluorescence spectrometry (EDXRF) may address this question and provide new answers and avenues of inquiry.ResultsOur study of 53 amphorae, produced during two important periods in the history of the workshop of Loron, has evidenced that even in chronologically closely related contexts of production chemical analysis could significantly separate samples according to production groups.ConclusionsThis result constitutes a very important first step towards a thorough study of the entire production history of the workshop, involving the creation of a comprehensive geochemical reference group comprising several hundred samples. This in turn will enable us to address an array of hypotheses concerning the economy and ecology of this production site, which are briefly presented in the article. The application of this methodology to the whole corpus of Istrian amphorae is then advocated in light of this study.