Repasch, Marisa N; Wittmann, Hella; Scheingross, Joel S; Sachse, Dirk; Szupiany, Ricardo N; Orfeo, Oscar; Fuchs, Margret C; Hovius, Niels (2020): Meteoric 10Be concentrations and OSL depositional ages of Rio Bermejo floodplain sediment [dataset]. PANGAEA, https://doi.org/10.1594/PANGAEA.913993

To determine the depositional age and the long-term delivery of meteoric 10Be (10Bem) to the Rio Bermejo floodplain (northern Argentina), we collected floodplain sediment samples at four locations identified as point bars of abandoned Rio Bermejo channels. We used a stainless-steel hand auger to collect sediment down to a maximum depth of ~5 m, or until refusal. For 10Bem and 9Bereac analysis, we extracted samples that integrated material from 0-20 cm below the surface, 20-50 cm, and regularly spaced 40 cm intervals for lower depths. We homogenized the material prior to packing into clean plastic bags. Sediment particle size distributions were measured on ~10 mg aliquots using a laser diffraction particle size analyzer (Horiba LA-950). The total reactive phase, including amorphous oxyhydroxides and crystalline oxide grain coatings, was extracted from the sediment samples using a procedure adapted from Wittmann et al. (2012, doi:10.1016/j.chemgeo.2012.04.031). 10Be was purified from the extracted material, spiked with a 9Be carrier solution containing 150 µg of 9Be, and packed into targets for AMS measurement at the University of Cologne Centre for Accelerator Mass Spectrometry (Cologne, Germany). 10Be/9Be measurements were normalized to the KN01-6-2 and KN01-5-3 standards (Dewald et al., 2013, doi:10.1016/j.nimb.2012.04.030) that are consistent with a 10Be half-life of 1.36 ± 0.07 x10 yrˉ¹ (Nishiizumi et al., 2007, doi:10.1016/j.nimb.2007.01.297). 10Bem was calculated from the normalized and blank-corrected 10Be/9Be ratios. The reported 1σ uncertainties include counting statistics and the uncertainties of both standard normalization and blank correction. Stable 9Be concentrations were measured on a separate aliquot of the sample solution using inductively coupled plasma optical emission spectroscopy (ICP-OES). Uncertainty of ICP-OES measurements was 5%.

We used coarse quartz grain OSL analysis to determine depositional ages for each floodplain core. For OSL analysis, we collected light-sealed samples by driving an opaque tube into our floodplain cores at two select depths in each core. OSL measurements were performed using a Risø DA 15 OSL/TL reader equipped with a 90Sr beta irradiator (4.9 Gy/min). OSL signals were stimulated with blue LEDs (470 nm, 50 s, 125 ºC) and detected through an optical filter (U 340 Hoya). For each sample, 40 aliquots were measured using the single-aliquot regenerative dose (SAR) protocol (Murray and Wintle, 2000, doi:10.1016/S1350-4487(03)00053-2) for equivalent dose determination.