Annual and inter?annual magnetic variations in varved clay

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Abstract
The Swedish foil piston corer is perfect for taking long oriented sediment cores. The paleomagnetism in three Swedish varved clay cores record the annual changes during periods of about 100–150 years. An 11‐yr sunspot cyclicity is well established in the magnetic records. The amplitude variations are large. In thick varves (proximal varves and drainage varves), the inter‐annual magnetic variations are recorded. The intensity shows a clear annual cyclicity (independent of sedimentological variations). Declination and inclination show an annual cyclicity, too. The amplitudes of the sunspot and annual cyclicities are too large solely to be the effect of ionization changes. Chemical‐physical environmental changes must have played an important role in both cases. The recorded annual and seasonal magnetic (NRM) fluctuations are so large in amplitude that they in unvarved sediments without good dating control might have been classified as “excursions”; or major secular variations.

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