Beryllium-10 in forams and marine sediments; a new chemo-stratigraphic tracer for the late quaternary

Levchenko, VA; Opdyke, BN; Fink, D; Mifsud, C; Williams, AA

Beryllium-10 in forams and marine sediments; a new chemo-stratigraphic tracer for the late quaternary

Date

2008-09

Authors

Publisher

Eleventh International Conference on Accelerator Mass Spectrometry

Abstract

The production rate of cosmogenic isotopes 10Be and 14C is influenced by varitions in the primary cosmic ray flux and by charges of the Earth's magnetic field, which has experienced a number of significant perturbations during the late Quaternary (e.g. Lashamp Mono Lake excursion, circa 41 ka BP). Understanding these changes and synchronising variations in palaeomagnetic intensity derived from various marine sediment cores can often help constrain the quality of 14C dating, particularly in the interval between 20 and 50 ka ago, and establish reliable chronologies for ocean sedimentation rate changes. A common proxy for these palaeomagnetic changes is atmospheric fallout of 10Be in bulk sediments. However terrigenous and recycled sediments also deliver high 10Be concentrations thus strongly complicating the process required to isolate direct atmospheric from continental derived 10Be. As an alternative to geochemical speciation, grain size or leaching procedures in sediments we suggest that changes in 10Be concentrations in planktonic foraminifera can be used as a global stratigraphic marker. We are investigating planktonic foraminifera collected from Core MD - 982167, which was recovered from the Scott Plateau in the Eastern Indian Ocean at latitude of 13° S. The MD- 982167 already has an established stable isotope stratigraphy and a high sedimentation rate of 10 to 20 cm per ka. Initial results of paired 14C and 10Be determinations in foraminifera and fine fraction of the core sediments as a function of core depth have been obtained and subsequently will be compared to palaeomagnetic measurements currently in progress. An improved chronology for this high resolution core that has recorded brief, less than one thousand year duration, climatic events during the studied time interval will allow much better correlation between marine sedimentary records and the detailed chronologies established from the ice cores.

Keywords

Beryllium 10, Sediments, Quaternary period, Tracer techniques, Carbon 14, Cosmic ray flux

Citation

Levchenko, V., Opdyke, B., Fink, D., Mifsud, C., & Williams, A. A. (2008). Beryllium-10 in forams and marine sediments; a new chemo-stratigraphic tracer for the late quaternary. Presentation to the 11th International Conference on Accelerator Mass Spectrometry (AMS-11), 14th – 19th September 2008. Rome, Italy: Spazio Etoile.