Communication Dans Un Congrès Année : 2024

New surface exposure age data using cosmogenic radionuclides 10Be and 14C to constrain the age of the last deglaciation in the Retezat Mts, Southern Carpathians, Romania

Résumé

The presence of cosmogenic radionuclide concentrations inherited from previous exposure(s) of glacially transported boulders and moulded bedrock surfaces may hinder the determination of the surface exposure age (SED) of the last phase of (de)glaciation. A previous study revealed that glacial landforms of the cirque area in the southern side of the Retezat Mountains (Southern Carpathians, Romania) hold significant amount inherited 10Be (t1/2=1.4 My), which was used for a tentative estimation of the amount of glacial erosion, assuming that the lowest 10Be concentration was representative of the true age of deglaciation (Ruszkiczay-Rüdiger et al., 2021, Geomorphology 384, 107719). In this study, a western valley, the Zlătuia-Dobrunu valley of the Retezat Mts was sampled for 10Be SED. The novel data are in agreement with the previous datasets suggesting that the most extended glaciers belonged to the Last Glacial Maximum. However, the old apparent exposure durations based on 10Be analysis of samples from the cirque area provided firm evidence for the presence of excessive abundances of cosmogenic 10Be in this valley as well. The use of the short-lived in situ produced 14C (t1/2= 5.7 ky) provides an independent age constraint for the timing of the last deglaciation, because all 14C inventories that might be inherited from a previous exposure would have already been decayed. As a consequence, the 14C concentrations are not biased by inheritance, thus i) enable the age determination of the landforms belonging to the last phases of deglaciation and ii) the 14C exposure ages compared to the 10Be data will allow an assessment of the inherited amount of 10Be and thus a more precise determination of the amount of glacial erosion. In this study the new 10Be and 14C SED ages will be presented together with the mapped glacial landforms, reconstructed paleoglaciers and their Equilibrium Line Altitudes. Funding: NKFIH FK124807, INSU/CNRS, ANR - “EQUIPEX Investissement d’Avenir”, IRD and CEA, the PNRR-III-C9-2022 - I8, no. 760055/23.05.2023, CF 253/29.11.2022. and Horizon 2020 grant 871149 ”EUROPLANET”.

Dates et versions

hal-04725135 , version 1 (08-10-2024)

Identifiants

Citer

Zsófia Ruszkiczay-Rüdiger, Zoltán Kern, Balázs Madarász, Petru Urdea, Régis Braucher, et al.. New surface exposure age data using cosmogenic radionuclides 10Be and 14C to constrain the age of the last deglaciation in the Retezat Mts, Southern Carpathians, Romania. European Geosciences Union General Assembly 2024 (EGU24), Apr 2024, Vienne, Austria. ⟨10.5194/egusphere-egu24-12758⟩. ⟨hal-04725135⟩
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