Over the last years, a great amount of information on the technical chaîne opératoire of LBA and EIA copper production in the Oberhalbstein/Val Surses mining district of the Grisons in the southeastern Swiss Alps could be gained through survey, field and laboratory work (Della Casa, Naef & Turck, Quat. Int., 2016). The main focus was on ore extracting (mines, spoil heaps), copper ore beneficiation and smelting (furnaces, slags) and ore/slag/copper characterization (mineralogy, geochemistry, lead isotopy).

However, beyond this technical part of the chaîne opératoire approach (the "length" according to Martinon-Torres, Gallaecia, 2011), a whole range of environmental and in particular social implications (the "width") need to be studied in order to understand the copper producing process as an element of a wider (Alpine) economic system: subsistence economy, social and political organization, knowledge bases, culture and beliefs… are all matters of discussion, in particular as the research status of the valley in terms of landscape and settlement archaeology is yet limited.

The scope of this contribution is to discuss the framework of a comprehensive contextual approach to copper mining, to outline a total system of later prehistoric Alpine economy incorporating research accomplished in other regions of the Grisons/the Alps, and also to draw on perspectives for future research.

“What do we know about prehistoric and historic mining and metallurgy in the Alps and their influence on society and environment?” The answer to this complicated question is simple: Still too little! In my “flash-talk”, I will point out some reasons for this state of research and talk about two departure points for future research. First, traditional research into prehistoric mining in the Alps focused on the technical processes rather than on the social organisation, the context and environment of metal production. In order to explore these aspects, it is necessary to investigate the mining camps and the settlements where metallurgical production took place. This type of integrated research, focusing on the scale, the organisation, the supply with food and fuel will be illustrated by as short presentation of the ongoing research project “Life and Work at the Bronze Age Mine of Prigglitz” (FWF P30289-G25). Interpretation of the influence on society and environment depends on the supposed scale of production, i.e. the number of labour involved, the amount of ore extracted, the duration of mining etc. (see poster presentation below). So interdisciplinary research is requested to confront these questions using quantitative approaches, which can be based on experimental work or on computer simulations (like agent-based modelling). The second point that could substantially improve our understanding of prehistoric and historic mining is a systematic comparison of both epochs. Unfortunately, the disciplines of prehistory and history build their pictures of the past on completely different sources (archaeological sources, including bioarchaeological and geoarchaeological research – versus written historical sources). It is time to bridge this gap by confronting both groups of sources (where available) and by drawing analogies with historic activities in the same region. Following this comparative approach, our knowledge of all periods can substantially advance and lead to surprising results.

Combining geophysical measurements and core drillings
to estimate scale and duration of a Bronze Age copper mine at Prigglitz-Gasteil

Peter Trebsche, Adrian Flores-Orozco, Ingrid Schlögel, Günther Weixelberger

Locating a prehistoric mine is difficult if there are no visible features in the surface morphology (e.g. sunken shafts) or if there are no historic records. We faced this problem when investigating the Late Bronze Age mining settlement of Prigglitz-Gasteil at the easternmost fringe of the Alps in Lower Austria. The site was occupied during the late Urnfield Period (ca 1050 to 900 BC). It reached a maximum extent of about 3 hectares, making it the largest known prehistoric mining settlement in Lower Austria. The site has yielded only indirect evidenced of copper ore extraction, in the form of huge piles of mining debris and some miners’ tools (antler picks and hammers) recovered during systematic excavations from 2010 to 2014.

Application of several prospection techniques, including terrain walking, aerial photography, LiDAR terrain modeling, geomagnetic surveys, and percussion drillings, has failed to delineate traces of copper mines. Therefore, in a current project funded by the Austrian Science Fund (FWF), different geophysical techniques and core drillings were conducted in 2017 and 2018 to investigate the stratigraphy of the mining dumps and locate the underground works and the copper vein.

Geophysical methods employed included Induced Polarization (IP) imaging and ground penetrating radar (GPR). The IP method is an extension of electrical resistivity tomography (ERT), and provides information of the electrical conductivity and capacitive properties of the subsurface. Electrical resistivity imaging enabled us to delineate the extension of the main geological units, as well as the position and geometry of the dump materials. Additionally, imaging of the polarization effect revealed significant anomalies related to subsurface areas with high volumetric content of metallic minerals. The seismic refraction and tomography results allowed us to distinguish the overburden (dump material) from the bedrock and aided in the interpretation of the IP imaging results.

After preliminary analyses of the geophysical results, we conducted two core drillings, which reached the underlying bedrock at 32 m and 37 m depth. The archaeological and geological interpretation of the two cores provided the key to the interpretation of the geophysical measurements. A series of radiocarbon dates from the drilling cores allows for a precise dating of the mines and the mining dumps in the frame of the late Urnfield Period.

A geochemical study of a peat core collected in the minerotrophic fen Siegmoos in Hallstatt (Upper Austria) reveals periods of intense anthropogenic activity in prehistoric times. As analyses (ICP-MS, XRF, SEM, FTIR) of anthropogenic tracer (Sb, Pb, Cu, Sn) and main elements, stable Pb isotopes ratios, mineral particles and the sorption capacity of humic substances imply, a first persistent period of relatively moderate anthropogenic activity, dated by 14C, associated with salt mining in Hallstatt started around 1850 BC. The period from Late Bronze Age to Early Iron Age is characterised by increased metal concentrations, culminating around 800 BC in an absolute Cu concentration that exceeds concentrations from recent surface samples by a factor of 7. A strong increase of the ash content in the middle section of the core, corresponding to ~ 1100 BC, is likely to be correlated with a catastrophic landslide that altered geomorphological conditions in the high valley. An interpretation of calculated Pearson`s correlation coefficients does not suggest a significant influence of humic substance on the enrichment of anthropogenic tracer elements. Lower sections of the core show considerably higher concentrations of main and trace elements and higher ash contents attributed to stronger groundwater influence.

Salt production in Hallstatt starts in the early Neolithic period. A first peak was reached from 1300 B.C., when massive interferences in the surrounding landscape are traceable. Since around 700 B.C. it seems, Hallstatt had some kind of monopoly. In a big radius, there are no other traces of salt production. It seems, all other salt deposits in the eastern alps were neither systematically prospected nor used, though there are a lot of other brine springs and deposits, worthy for mining. That is surprising, because in other regions, like e.g. Siebenbürgen and neighboring Ukraine, several salt producers were producing on minimum space.
What is behind this unique position in salt production in the eastern alps? Why is Hallstatt able to be the only producer for so long?
Since from 700 B.C. on, the situation is changing. In direct neighbourhood, other production sites arise – Dürrnberg, Unken and Halltal. Every one of this producers is working with a different technique. Apparently, there was no transfer of technologies among the sites. In contrast to copper mining in the eastern alps, which appear to work with very similar techniques on every site.

Archaeological evidence suggests a specific “Alpine cultural group” in the Eastern Alps during the Copper Age (from 3500-2500 cal BC). A local cultural group is well documented for the following Bronze Age in the eastern Italian Alps, Tyrol and in part of Switzerland (e.g. vases cylindrical walls). Furthermore, geochemical studies on different copper artefacts from these areas indicates a common origin of the copper. On the other hand, specific cultural objects (e.g. axe eye shape) as well as mixed funerary rituals, suggests several contacts with people of different cultures from east and west Europe.
The Tyrolean Iceman (3360-3100 cal. BC) is the best representative of the Copper Age in the Eastern Alps. Besides the Iceman, only one Mesolithic sample (Veneto Dolomites) has been analysed for the genomic variation. Therefore there is a lack of ancient genomic data from this area. Comparison with published genomic data, have shown that the Iceman clusters with Early Neolithic farmers from different parts of Europe and with Neolithic individuals from Anatolia. In addition, European individuals contemporary of the Iceman cluster together. The latter also differ from the Iceman in their ancestry and genomic admixture patterns.
Since the Iceman alone cannot be considered as representative of the genomic diversity of this alpine area, we are analysing additional prehistoric individuals from the Iceman´s territory (from the Copper to the Early Bronze Age). The analyses will allow to explore the existence of specific copper age “alpine group” with alpine samples genetically differentiated from other individuals from Europe from the same time period. Moreover, by dissecting the ancestral genomic components of additional ancient alpine samples, the study will better clarified the genomic structure of prehistoric Alps and will help understanding main demographic events that occurred in Europe during this crucial phase of the human prehistory.