Application of self-absorption correction method in gamma spectroscopy for²¹⁰Pb and¹³⁷Cs sediment chronology on the continental slope off NW Africa

Abstract

The uppermost 50 cm of the high resolution core GeoB9501-4 from the continental slope off NW Africa has been used for improving routine technique of 210 Pb and 137 Cs sediment chronology in the Radioactivity measurement laboratory of the Bremen University. The experimental requirements for 210 Pb and 137 Cs determination were non-destructive analysis of wet sediment samples in cylindrical containers with different heights, unknown elemental composition and density. The method used in this study to deal with self attenuation is applying efficiencies calculated using the LabSOCS TM , Genie 2000 software calibration tool, validated by self-absorption test measurements of different materials with known composition. A mean sedimentation rate of 0.49 cm • yr −1 was obtained from the investigated core using the CRS chronological model. This means a relatively increased recent sedimentation rate comparing to an average sedimentation rate at higher depths of an associated gravity core estimated to 0.15 cm • yr −1 by 14 C chronology. A further increase of the sedimentation rate was observed in the uppermost part of the studied core (up to 0.90 cm • yr −1 ).

Orbital‐ and Millennial‐Scale Variability in Northwest African Dust Emissions Over the Past 67,000 years

“…The chronologies for the CHEETA cores were developed from existing AMS radiocarbon ages from GC37, GC49, and GC68, taken from McGee et al (2013) and Tierney, Pausata, and deMenocal (2017) (see Figure S1 in Supporting Information S1). Radiocarbon ages were converted to calendar ages using Marine13 (Reimer et al, 2013), with an additional reservoir correction (ΔR) of 130 ± 50 years (2σ) based upon local modern reservoir ages (Mulitza et al, 2010;Ndeye, 2008;Pittauerov et al, 2009). We do not attempt to estimate past changes in reservoir age, though these most certainly accompanied the dramatic changes in upwelling observed in African margin records (Bradtmiller et al, 2016;Romero et al, 2008).…”

Reconstructing atmospheric changes in Monsoon regions using eolian dust

“…The ages for this study were determined on specimens of Globigerina bulloides; radiocarbon measurements were performed at the Center for Accelerator Mass Spectrometry at Lawrence Livermore National Laboratory. Radiocarbon ages were converted to calendar ages using Marine13 (Reimer et al, 2013), with an additional reservoir correction (ΔR) of 130 ± 50 yr (2σ) based upon local modern reservoir ages (Mulitza et al, 2010;Ndeye, 2008;Pittauerov et al, 2009). We do not attempt to estimate past changes in reservoir age, though these most certainly accompanied the dramatic changes in upwelling observed in African margin records (Bradtmiller et al, 2016;Romero et al, 2008).…”

Quality Assurance in Gamma-Ray Spectrometry of Seabed Sediments

“…In this case, the self-attenuation factor can be calculated from , [10] where A and A 0 are the peak count rates for the actual sample and a reference sample, respectively. Two basic approaches have been applied for solving the problem of self-attenuation in the volume of a sample: experimental (6, 7) and mathematicalusing Monte Carlo simulations (1,8).…”

“…The level of self-attenuation depends on a number of parameters, for example on sample geometry and on μ which, in turn, depends on material density, sample composition, and photon energy (2). The corrected peak areas are the spectrum peak areas multiplied by the correction as (5): , [8] where:…”