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| Titel |
Towards a strontium isoscape for the determination of provenance of prehistoric wooden findings |
| VerfasserIn |
Monika Horsky, Johannes Tintner, Monika Bolka, Michael Grabner, Kerstin Kowarik, Hans Reschreiter, Anton Kern, Micha Horacek, Thomas Prohaska |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250091033
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| Publikation (Nr.) |
 EGU/EGU2014-5299.pdf |
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| Zusammenfassung |
| Prehistoric wood artefacts have been excavated from ancient salt mine galleries in Hallstatt,
Austria. These findings present a unique archive of information on Bronze and Iron
Age mining and trade relations, as for certain tools a production elsewhere and
transport to the mine is assumed. These wooden artefacts contain the geochemical
information of their growth location, though masked by secondary salts due to the storage
conditions. Consequently, the analysis of the biogenic 87Sr/86Sr isotope ratios of
the findings was carried out in comparison to the respective signatures of trees
from possible regions of origin, in order to draw conclusions on prehistoric trade
routes.
Thus - in addition to Hallstatt - seven regions in the Alpine region of Austria as well as in
the Northern and Southern lowlands were selected based on known settlements in the time
period of interest. Within all regions, the geological bedrock variability was considered for
the definition of sampling spots, which resulted in a total of 26 locations. Four tree species
represented in the archaeological finds (i.e. Picea abies, Abies alba, Fagus sylvatica and
Quercus sp.) were sampled upon availability. Wood sample digests from eight replicate trees
per location were analysed using multicollector-inductively coupled plasma-mass
spectrometry (MC-ICP-MS).
In order to reveal the biogenic signatures of the prehistoric findings, a decontamination
method based on acid leaching was developed. We could successfully separate biogenic from
secondary Sr and adopted a mixing theory to account for possibly incomplete removal of the
latter.
The Sr isotope ratio data obtained from modern trees (i.e. bioavailable Sr) reflect the
geological heterogeneity of the Alps, which challenges the creation of an isoscape and its
applicability to distinct provenance determination. Different geologic bedrock types can be
clearly distinguished by their 87Sr/86Sr, e.g. marine sedimentary and igneous rocks.
Furthermore, the data indicate that the spread of isotope ratios within one geological
substrate also varies strongly depending on its type: it is much narrower for trees
grown on e.g. carbonate than for those on silicate bedrocks. The results highlight
the importance to consider even small scale geological variability for a reliable
application of Sr isotope ratio measurements to the determination of origin of biogenic
material. |
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