, Volume 19, Issue 4, pp 527-536

Solar variability and ring widths in fossil trees

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Summary

We have analysed ring width sequences of 1.3 My old fossil trees, grown with no water deficit, in Dunarobba forest (Italy). We find evidence for a modulation period of the annual ring growth widths on time scale of 11 y to 15 y. Since similar modulation cycles have also been found by other authors in polar ice10Be concentration of the last millennium and in a series of annual ring widths of a same kind of trees grown in Central Europe of 15–20 My ago, we suggest that such cycles might be related to solar-activity cycles. This would support the hypothesis of a quasi-periodic behaviour of the solar dynamical system controlled by an oscillator whose fundamental period is of 22–25y, that can be identified with the Hale cycle; this system would be operational at least since the Miocene era.