Publication Date:
2020-06-12
Description:
The production rate of cosmogenic radionuclides such as 10Be or 14C is known to
vary as a function of the geomagnetic field intensity. It should, therefore, be possible
to extract a record of palaeofield intensity from the deposition record of these
radionuclides in marine or terrestrial sediments and ice cores. Field intensity variations,
however, are not the only factor that has influenced the cosmogenic radionuclide
records. In the case of 14C, variations of the global carbon cycle, caused by
reorganization of the ocean circulation patterns from the last glacial to the present
interglacial, are superimposed. 10Be is not affected by these variations because it is
not part of the carbon cycle, but its deposition rates in marine sediments vary as
a function of lateral sediment redistribution and boundary scavenging intensity. A
global stacked record of 10Be deposition rates, corrected for sediment redistribution
by normalizing to 230Thex, was shown to remove most of the disturbances, and provides
a record of 10Be production rate variations over the last 200 000 years, which
translates into geomagnetic field intensity variations. This dataset is compared with
palaeofield intensities reconstructed from marine sediments by palaeomagnetic methods,
from variations in atmospheric 14C/12C derived from independent calibrations
of 14C ages, such as U/Th dating and tree ring chronology, and from 36Cl and 10Be
fluxes in polar ice cores. Potential influences of the Earth’s orbital parameters and
insufficient correction for orbitally triggered climate variations on the palaeointensity
reconstructions are assessed. It is argued that the palaeointensity records derived
from marine sediments are not significantly affected by these factors.
Type:
Article
,
PeerReviewed
Format:
text
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