Exploring the potential of luminescence methods for dating Alpine rock glaciers |
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| Institution: | 1. Division of Organic Chemistry and Biochemistry, Ru?er Bo?kovi? Institute, Bijeni?ka 54, 10000 Zagreb, Croatia;2. Biorobotics Laboratory, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland;3. Division of Analytical Chemistry, Department of Chemistry, Faculty of Science, University of Zagreb, Horvatovac 102a, 10000 Zagreb, Croatia;1. Department of Geosciences, National Taiwan University, Taipei 106, Taiwan;2. Physics Department, University of Arizona, AZ 85721-0081, USA;3. Department of Earth Sciences, Indian Institute of Science Education and Research—Kolkata, 741252, India;4. Division of Geological and Planetary Sciences, California Institute of Technology, CA 91125, USA;5. State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, Beijing 100029, China;6. Institute of Crustal Dynamics, China Earthquake Administration, Beijing 100085, China;7. Institute of Geology and Geophysics, Chinese Academy of Science, Beijing 100029, China;8. Seismological Bureau of Tibet Autonomous Region, Lhasa, China |
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| Abstract: | Rock glaciers contain valuable information about the spatial and temporal distribution of permafrost. The wide distribution of these landforms in high mountains promotes them as useful archives for the deciphering of the environmental conditions during their formation and evolution. However, age constraints are needed to unravel the palaeoclimatic context of rock glaciers, but numerical dating is difficult. Here, we present a case study assessing the potential of luminescence techniques (OSL, IRSL) to date the inner sand-rich layer of active rock glaciers. We focus on the signal properties and the resetting of the signal prior to deposition by investigating single grains. While most quartz shows low signal intensities and problematic luminescence characteristics, K-feldspar exhibits much brighter and well-performing signals. Most signals from plagioclases do not show suitable properties. Luminescence signals far below saturation indicate distinct but differential bleaching. The finite mixture model was used to determine the prominent populations in the equivalent dose distributions. The luminescence ages represent travel times of grains since incorporation into the rock glacier and hence, minimum ages of rock glacier formation. Luminescence ages between 3 ka and 8 ka for three rock glaciers from the Upper Engadine and Albula region (Swiss Alps) agree well with independent age estimates from relative and semi-quantitative approaches. Therefore, luminescence seems to have the potential of revealing age constraints about processes related to the formation of rock glaciers, but further investigations are required for solving some of the problems remaining and reducing the dating uncertainties. |
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| Keywords: | Rock glacier Luminescence dating OSL IRSL Single grains Alps |
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