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Enhanced cosmic‐ray production of 10 Be coincident with the Mono Lake and Laschamp Geomagnetic Excursions
Author(s) -
McHargue Lanny R.,
Damon Paul E.,
Donahue Douglas J.
Publication year - 1995
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/95gl00169
Subject(s) - earth's magnetic field , geology , varve , cosmic ray , excursion , paleomagnetism , cosmogenic nuclide , geomagnetic secular variation , flux (metallurgy) , geophysics , paleontology , geomagnetic storm , astrophysics , physics , magnetic field , quantum mechanics , sediment , political science , law , materials science , metallurgy
The cosmogenic isotope 10 Be, total Be, and Al were measured in partly varved sediments from the upper 50 m of core 480, leg 64 (DSDP), Gulf of California. The concentration of 10 Be from 1 to 50 kyr is in general agreement with estimates of the geomagnetic dipole moment obtained from archaeomagnetic and marine core research. 10 Be anomalies were also found at 32 kyr and 43 kyr, contemporaneous with the Mono Lake and Laschamp excursions, respectively. The production of 10 Be required to explain these anomalies is too high, particularly for the Mono Lake excursion, to be produced by a combination of decreased geomagnetic field and unprecedented long‐term solar activity. We conclude that the cause is a change in the galactic cosmic‐ray flux consistent with a supernova event. The coincidence with the two excursions remains a paradox.