Atmospheric Be-10 as a stratigraphic tracer and climate indicator

Category Paleontology and Stratigraphy
Group GSI.IR
Location International Geological Congress,oslo 2008
Author Graham, Ian۱; Ditchburn, Robert۱; Carter, Robert۲
Holding Date 17 September 2008

The cosmogenic isotope Be-10 (10Be), produced in the upper atmosphere through the interaction of cosmic rays with 16O, can be measured with great precision in marine and terrestrial sedimentary deposits. With a half-life of c. 1.5 Myr, Be-10 has proved to be particularly useful as a stratigraphic tracer for climate-related research covering the past c. 10–15 million years and, particularly, the past several hundred thousand years. There are a number of key factors that influence the measured concentration of atmospheric Be-10 in sedimentary deposits. These include variations in galactic cosmic ray flux, solar cosmic ray flux, and the geomagnetic field, as well as the Be-10 adsorption rate onto mineral grains, which is related to mineralogy, grainsize and/or sedimentation rate, and the analytical process itself. These various factors will be discussed in relation to global and New-Zealand-based studies of deep-sea cores, basin sequences, soils, ferromanganese deposits and atmospheric fallout. Through targeted analytical procedures and careful consideration of non-solar influences, it should be possible to extract climatic influences from the Be-10 stratigraphic record, which can be attributed to solar forcing. This has been attempted, with some success, by a number of researchers in relation to particular marine sediment cores which, after geomagnetic field variations are accounted for, and the data corrected for sediment transport, yield a Be-10 production signal consistent with global theoretical models. These individual studies carry a relatively large uncertainty, however, and the combination of multiple highly-resolved Be-10 records may lead to a significantly improved reconstruction of cosmic ray flux over the recent geological past.