20-EPN2-031: Determination of the Timing of the Final Deglaciation and the Depth of Subglacial Erosion Using In-Situ Produced Cosmogenic ¹⁴C in Combination with Existing Cosmogenic ¹⁰Be Data

Visit by Régis Braucher of Cerege CNRS-Aix-Marseille University (France) to TA2 Facility 16 – Carbon-14 Dating AMS Laboratory (Hungary).
Dates of visit: 12 – 16 December 2022.

Report Summary: Glacial landforms formed during the last deglaciation in several valleys of the Retezat Mts (Southern Carpathians) have been dated by in situ produced cosmogenic ¹⁰Be. A bias towards old exposure ages has hindered the age determination of the last deglaciation phases (Ruszkiczay-Rüdiger et al., 2021, Geomorphology, 107719).

The measurement of the concentrations of the short-lived in situ produced ¹⁴C concentrations in the framework of the TA visit enables us to estimate the true age of these landforms and also allows the quantification of the amount of inherited ¹⁰Be. This inherited nuclide inventory is used to estimate the depth of subglacial erosion during the last glacial phase, a parameter that was not yet quantified in the region yet. Sixteen quartz samples (mass: 4-5 g) were analysed in the framework of this project in the Isotoptech AMS Laboratory (Debrecen, HU). All samples gave a reliable C yield (between 40-10 ug/sample). A special Gas ion source interface (GIS) and accelerator mass spectrometer (AMS) coupling technique enabled us to quantify the ¹⁴C/¹²C ratio in the small sized CO₂ samples. AMS ¹⁴C sample preparation and analyses was controlled by reference material preparations and parallel analyses. The resulted ¹⁴C data (fractionModern) now can be used for a more realistic exposure age determination and estimation of the depth of subglacial erosion in the Retezat Mts. This is the first application of the ¹⁰Be-¹⁴C nuclide pair in Eastern Central Europe.

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