Cosmogenic ³He paleothermometry on post-LGM glacial bedrock within the central European Alps

Abstract 3 He in quartz at Earth surface temperatures offer the potential to directly reconstruct the evolution of past in situ temperatures from formerly glaciated areas, which is important information for improving our understanding of glacier–climate interactions. In this study, we apply cosmogenic 3 He  paleothermometry to rock surfaces gradually exposed from the Last Glacial Maximum (LGM) to the Holocene period along two deglaciation profiles in the European Alps (Mont Blanc and Aar massifs). Laboratory experiments conducted on one representative sample per site indicate significant differences in 3 He  diffusion kinetics between the two sites, with quasi-linear Arrhenius behavior observed in quartz from the Mont Blanc site and complex Arrhenius behavior observed in quartz from the Aar site, which we interpret to indicate the presence of multiple diffusion domains (MDD). Assuming the same diffusion kinetics apply to all quartz samples along each profile, forward model simulations indicate that the cosmogenic 3 He abundance in all the investigated samples should be at equilibrium with present-day temperature conditions. However, measured cosmogenic 3 He  concentrations in samples exposed since before the Holocene indicate an apparent 3 He thermal signal significantly colder than today. This observed 3 He thermal signal cannot be explained with a realistic post-LGM mean annual temperature evolution in the European Alps at the study sites. One hypothesis is that the diffusion kinetics and MDD model applied may not provide sufficiently accurate, quantitative paleo-temperature estimates in these samples; thus, while a pre-Holocene 3 He thermal signal is indeed preserved in the quartz, the helium diffusivity would be lower at Alpine surface temperatures than our diffusion models predict. Alternatively, if the modeled helium diffusion kinetics is accurate, the observed 3 He abundances may reflect a complex geomorphic and/or paleoclimatic evolution, with much more recent ground temperature changes associated with the degradation of alpine permafrost.

Angaben zum Objekt

• Standort: Deutsche Nationalbibliothek Frankfurt am Main
• Umfang: Online-Ressource
• Sprache: Englisch

Verweise und Beziehungen

• Erschienen in: Cosmogenic ³He paleothermometry on post-LGM glacial bedrock within the central European Alps ; volume:4 ; number:2 ; year:2022 ; pages:641-663 ; extent:23 ; Geochronology ; 4, Heft 2 (2022), 641-663 (gesamt 23)

Beteiligte, Orts- und Zeitangaben

• Urheber: Gribenski, Natacha ; Tremblay, Marissa M. ; Valla, Pierre G. ; Balco, Greg ; Guralnik, Benny ; Shuster, David L.

Weitere Informationen

• DOI: 10.5194/gchron-4-641-2022
• URN: urn:nbn:de:101:1-2022111004205514585728
• Rechteinformation: Open Access; Der Zugriff auf das Objekt ist unbeschränkt möglich.
• Letzte Aktualisierung: 15.08.2025, 07:33 MESZ