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Science 17 April 1992:
Vol. 256. no. 5055, pp. 356 - 357
DOI: 10.1126/science.256.5055.356
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Articles

40Ar/39Ar Dating of the Brunhes-Matuyama Geomagnetic Field Reversal

A. K. Baksi 1, V. Hsu 2, M. O. McWilliams 3, and E. Farrar 4

1 Department of Geology and Geophysics, Louisiana State University, Baton Rouge, LA 70803
2 Air Force Technical Applications Center, Patrick Air Force Base, FL 32925
3 Department of Geophysics, Stanford University, Stanford, CA 94305
4 University, Kingston, Ontario, Canada K7L 3N6

Magnetostratigraphic studies are widely used in conjunction with the geomagnetic polarity time scale (GPTS) to date events in the range 0 to 5 million years ago. A critical tie point on the GPTS is the potassium-argon age of the most recent (Brunhes-Matuyama) geomagnetic field reversal. Astronomical values for the forcing frequencies observed in the oxygen isotope record in Ocean Drilling Project site 677 suggest that the age of this last reversal is 780 ka (thousand years ago), whereas the potassium-argon-based estimate is 730 ka. Results from 4039; Ar incremental heating studies on a series of lavas from Maui that straddle the Brunhes-Matuyama reversal give an age of 783 + 11 ka, in agreement with the astronomically derived value. The astronomically based technique appears to be a viable tool for dating young sedimentary sequences.


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