Small aliquot and single grain IRSL and post-IR IRSL dating of fluvial and alluvial sediments from the Pativilca valley,Peru |
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| Institution: | 1. Institute of Geological Sciences, University of Bern, Baltzerstrasse 1+3, 3012 Bern, Switzerland;2. Oeschger Centre for Climate Change Research, University of Bern, Zaehringerstrasse 25, 3012 Bern, Switzerland;3. Department of Physical Geography and Quaternary Geology, Stockholm University, 10691 Stockholm, Sweden;1. Museo Nacional de Ciencias Naturales, CSIC, Serrano 115 bis, 28006 Madrid, Spain;2. Center for Nuclear Technologies, Technical University of Denmark, DTU Risø Campus, Frederiksborgvej 399, 4000 Roskilde, Denmark;3. Nordic Laboratory for Luminescence Dating, Department of Earth Sciences, Århus University, Risø, Frederiksborgvej 399, 4000 Roskilde, Denmark;1. Centre for Science, Athabasca University, 1 University Drive, Athabasca, Alberta T9S 3A3, Canada;2. Earth and Atmospheric Science, University of Alberta, Edmonton, Alberta T6G 2E3, Canada;1. Department of Earth Sciences, ETH, 8092 Zürich, Switzerland;2. Centre for Nuclear Technologies, DTU–Risø, Frederiksborgvej 399, Building 201, 4000 Roskilde, Denmark;3. Soil Geography and Landscape group and the Netherlands Centre for Luminescence Dating, Wageningen University, Droevendaalsesteeg 3, 6708PB Wageningen, The Netherlands;4. Institute of Earth Surface Dynamics, University of Lausanne, Geopolis, 1015 Lausanne, Switzerland;5. Nordic Laboratory for Luminescence Dating, Aarhus University, Frederiksborgvej 399, Building 201, 4000 Roskilde, Denmark;6. Institute of Earth and Environmental Sciences – Geology, University of Freiburg, Albertstr. 23b, 72104 Freiburg, Germany;7. Raymond and Beverly Sackler School of Physics and Astronomy, Tel Aviv University, Tel Aviv 69978, Israel;8. Institute of Geological Sciences, University of Bern, Baltzerstrasse 1+3, 3012 Bern, Switzerland;9. Department of Earth, Planetary, and Space Sciences, UCLA, Los Angeles, CA 90095-1567, USA;10. Department of Geography, University of Sheffield, Sheffield S10 2TN, UK;1. Center for Nuclear Technologies, Technical University of Denmark, DTU Risø Campus, DK-4000 Roskilde, Denmark;2. Institut de Recherche sur les Archéomatériaux, UMR 5060 CNRS – Université de Bordeaux, Centre de Recherche en Physique Appliquée à l''Archéologie (CRP2A), Esplanade des Antilles, Maison de l''archéologie, 33607 Pessac Cedex, France;3. Nordic Laboratory for Luminescence Dating, Department of Geoscience, Aarhus University, DTUNutech, Risø Campus, DK-4000 Roskilde, Denmark;1. U.S. Geological Survey, Box 25046, MS 974, Denver Federal Center, Denver, CO 80225, USA;2. Cooperative Institute for Environmental Research, University of Colorado – Boulder, CO 80302, USA;1. Institute for Geology, University of Innsbruck, Innrain 52, 6020 Innsbruck, Austria;2. GeoQuest Research Centre, School of Earth and Environmental Sciences, University of Wollongong, Northfields Avenue, Wollongong, NSW 2500, Australia;3. Scarp Archaeology, PO Box 191, Terrey Hills, NSW 2084, Australia;4. College of Arts, Society and Education, James Cook University, PO Box 6811, Cairns, QLD 4870, Australia;5. Department of Anthropology, University of Washington, Seattle, WA 98195-3100, USA |
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| Abstract: | Infrared stimulated luminescence (IRSL) and post-IR IRSL are applied to small aliquots and single grains to determine the equivalent dose (De) of eleven alluvial and fluvial sediment samples collected in the Pativilca valley, Central Peru at ca. 10°S latitude. Small aliquot De distributions are rather symmetric and display over-dispersion values between 15 and 46%. Small aliquot g-values range between 4 and 8% per decade for the IRSL and 1 and 2% per decade for the post-IR IRSL signal. The single grain De distributions are highly over-dispersed with some of them skewed to higher doses, implying partial bleaching; this is especially true for the post-IR IRSL. Measurements of a modern analog reveal that residuals due to partial bleaching are present in both the IRSL as well as the post-IR IRSL signal. The g-values of individual grains exhibit a wide range with high individual uncertainties and might contribute significantly to the spread of the single grain De values, at least for the IRSL data. Electron Microprobe Analysis performed on single grains reveal that a varying K-content can be excluded as the origin of over-dispersion. Final ages for the different approaches are calculated using the Central Age Model and the Minimum Age Model (MAM). The samples are grouped into well-beached, potentially well-bleached and partially bleached according to the evaluation of the single grain distributions and the agreement of age estimates between methods. The application of the MAM to the single grain data resulted in consistent age estimates for both the fading corrected IRSL and the post-IR IRSL ages, and suggests that both approaches are suitable for dating these samples. |
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| Keywords: | K-rich feldspar IRSL Post-IR IRSL Small aliquots Single grains Over-dispersion Minimum age model K-content Fading |
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