Application of self-absorption correction method in gamma spectroscopy for ²¹⁰Pb and ¹³⁷Cs sediment chronology on the continental slope off NW Africa

¹ Institute of Environmental Physics, University of Bremen, 28334 Bremen, Germany
² MARUM, University of Bremen, 28359 Bremen, Germany

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 ²¹⁰Pb and ¹³⁷Cs sediment chronology in the Radioactivity measurement laboratory of the Bremen University. The experimental requirements for ²¹⁰Pb and ¹³⁷Cs 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 ¹⁴C 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).