Regional beryllium-10 production rate for the mid-elevation mountainous regions in central Europe, deduced from a multi-method study of moraines and lake sediments in the Black Forest

oleh: F. M. Hofmann, C. Rambeau, L. Gegg, M. Schulz, M. Steiner, A. Fülling, L. Léanni, F. Preusser

Format: Article
Diterbitkan: Copernicus Publications 2024-05-01

Deskripsi

<p>Beryllium-10 cosmic-ray exposure (CRE) dating has revolutionized our understanding of glacier fluctuations around the globe. A key prerequisite for the successful application of this dating method is the determination of regional production rates of in situ accumulated <span class="inline-formula"><sup>10</sup></span>Be, usually inferred at independently dated calibration sites. Until now, no calibration site has been available for the mid-elevation mountain ranges of central Europe. We fill this gap by determining in situ <span class="inline-formula"><sup>10</sup></span>Be concentrations in large boulders on moraines and by applying radiocarbon and infrared-stimulated luminescence (IRSL) dating to stratigraphically younger lake sediments in the southern Black Forest, SW Germany. The dating methods yielded concordant results, and, based on age–depth modelling with <span class="inline-formula"><sup>14</sup></span>C ages, the age of a cryptotephra, and IRSL ages, we deduced a regional <span class="inline-formula"><sup>10</sup></span>Be production rate in quartz. Calibrating the Black Forest production rate (BFPR) in the Cosmic-Ray Exposure program (CREp) resulted in a spallogenic sea-level and high-latitude (SLHL) production rate of <span class="inline-formula">3.64±0.11</span> atoms <span class="inline-formula"><sup>10</sup></span>Be g<span class="inline-formula"><sup>−1</sup></span> quartz a<span class="inline-formula"><sup>−1</sup></span> when referring to time-dependent Lal–Stone scaling, the European Reanalysis (ERA)-40 atmosphere model, and the atmospheric <span class="inline-formula"><sup>10</sup></span>Be-based geomagnetic database in CREp. The BFPR turned out to be <span class="inline-formula">∼11</span> % lower than both those at the nearest calibration site in the Alps (<span class="inline-formula">4.10±0.10</span> atoms <span class="inline-formula"><sup>10</sup></span>Be g<span class="inline-formula"><sup>−1</sup></span> quartz a<span class="inline-formula"><sup>−1</sup></span> at SLHL) and the canonical global <span class="inline-formula"><sup>10</sup></span>Be production rate (<span class="inline-formula">4.11±0.19</span> atoms <span class="inline-formula"><sup>10</sup></span>Be g<span class="inline-formula"><sup>−1</sup></span> quartz a<span class="inline-formula"><sup>−1</sup></span> at SLHL) in CREp. A stronger weathering and snow cover bias and a higher impact of forest, soil, moss, and shrub cover at the study site likely explain this discrepancy.</p>