The proper choice of proxies for relevant strontium isotope baselines used for provenance and mobility studies in glaciated terranes – Important messages from Denmark
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Strontium (Sr) isotope based provenance and mobility studies of ancient humans and animals necessitate representative isoscapes/baselines. However, regions/terranes that were shaped and affected by glaciers during the last Ice Ages and are covered by glaciogenic sediments present a challenge with regards to the choice of suitable surface proxy archives. Recent studies proposed that only 87Sr/86Sr signatures from pristine areas are relevant for this purpose. To test this theory, 160 new Sr concentrations [Sr] and 87Sr/86Sr signatures composed from ~960 subsamples of soil leachates and plants, complemented with 55 surface waters from agriculturally unaffected pristine forest sites from all over Denmark (island of Bornholm excluded) were analyzed. The results reveal that average 87Sr/86Sr signatures of all three proxies (plants: 0.7115 ± 0.0025; 2σ, n = 162; soil leachates: 0.7118 ± 0.0037; 2σ; n = 161, surface waters: 0.7104 ± 0.0030; 2σ, n = 55) are elevated compared to larger water bodies (creeks, rivers, lakes). In mixing diagrams, the data converge in a shared high [Sr] low 87Sr/86Sr endmember, which points to either remnant natural carbonates and/or organic components retaining carbonate Sr in the studied Podzols/Luvisols. The indications for more abundant carbonates in the past, compared to today's acid leached soils, implies that 87Sr/86Sr values measured from pristine forest locations and heathlands do not adequately reflect the biosphere compositions that prevailed ~12,000–2000 thousand years ago. Consequently, pristine forests in Denmark seem to be unsuitable proxy archive environments for constructing Sr isotope baselines for determining the provenance and mobility of ancient humans and animals. Hence, 87Sr/86Sr values measured in these pristine areas are non-representative and inadequate, and their use will lead to wrong interpretations. Finally, our study sheds light on the complexity of defining relevant and representative isoscapes/baselines in significantly changing environments and areas where the surface biosphere conditions do not necessary reflect the underlying geology.
| Original language | English |
|---|---|
| Article number | 153394 |
| Journal | Science of the Total Environment |
| Volume | 821 |
| Number of pages | 13 |
| ISSN | 0048-9697 |
| DOIs | |
| Publication status | Published - 15 May 2022 |
Bibliographical note
Funding Information:
This research was made possible through the support of The Carlsberg Foundation ?Semper Ardens? research CF18-0005 (?Tales of Bronze Age People? to Karin Margarita Frei) for which we are very thankful. We wish to thank Pernille Ladegaard-Pedersen from the National Museum of Denmark for processing a large number of samples from Jutland through the laboratory procedures. Ryan Bond is thanked for his assistance in the field, and Cristina Nora Jensen and Toby Leeper for highly qualified laboratory and mass spectrometer assistance at the Isotope Laboratory of the Department of Geosciences and Natural Resource Management at University of Copenhagen. We also thank Trygvi Bech ?rting for help with geostatistics and for creating the kriged maps, and T. Douglas Price for providing a workable diagram for Fig. 6. Two anonymous reviewers are thanked for their constructive comments, and editor Mae Sexauer Gustin contributed with helpful input during the revision. Kriged maps were created using ArcGIS? software by Esri. ArcGIS? and ArcMap? are the intellectual property of Esri and used herein under license. Copyright ? Esri. All rights reserved. KMF designed, planned and administered the project. KMF, RF and ABF conducted fieldwork and processed the samples through the labs. RF did the mass spectrometric analyses. RF produced the first manuscript draft, and RF, KMF and ABF substantially complemented and edited the draft thereafter. Funding of the project was through a grant assigned to KMF.
Funding Information:
This research was made possible through the support of The Carlsberg Foundation “Semper Ardens” research CF18-0005 (“Tales of Bronze Age People” to Karin Margarita Frei) for which we are very thankful. We wish to thank Pernille Ladegaard-Pedersen from the National Museum of Denmark for processing a large number of samples from Jutland through the laboratory procedures. Ryan Bond is thanked for his assistance in the field, and Cristina Nora Jensen and Toby Leeper for highly qualified laboratory and mass spectrometer assistance at the Isotope Laboratory of the Department of Geosciences and Natural Resource Management at University of Copenhagen. We also thank Trygvi Bech Árting for help with geostatistics and for creating the kriged maps, and T. Douglas Price for providing a workable diagram for Fig. 6 . Two anonymous reviewers are thanked for their constructive comments, and editor Mae Sexauer Gustin contributed with helpful input during the revision. Kriged maps were created using ArcGIS® software by Esri. ArcGIS® and ArcMap™ are the intellectual property of Esri and used herein under license. Copyright © Esri. All rights reserved.
Publisher Copyright:
© 2022 The Authors
- Baselines, Denmark, Isoscapes, Pristine forest locations, Soil-plant-surface water proxies, Strontium isotopes
Research areas
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