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Geophys. J. Int. (1997)129, 176--182 On the construction of geomagnetictimescales from non-prejudicial

Summary: Geophys. J. Int. (1997)129, 176--182
On the construction of geomagnetictimescales from non-prejudicial
treatment of magnetic anomaly data from multipleridges
Stephen P. Huestis' and Gary D. Acton2
Dapartment of Earth and Planetary Sciences, Uninersity of New Mexico, Albuquerque, NM 87131, USA
ODPITexas A&M University, 1000Discovery Driue, College Station, TX 77845, USA
Accepted 1996December 3. Received 1996 October 18;in original form 1996May 23
When marine magnetic-anomaly data are used to construct geomagnetic polarity
timescales, the usual assumption of a smooth spreading-rate function at one seafloor
spreading ridge forces much more erratic rate functions at other ridges. To eliminate
this problem, we propose a formalism for the timescale problem that penalizes
non-smooth spreading behaviour equally for all ridges. Specifically, we establish a
non-linear Lagrange multiplier optimization problem for finding the timescale that
(1) agrees with known chron ages and with anomaly-interval distance data from
multiple ridges and (2)allows the rate functions for each ridge to be as nearly constant
as possible, according to a cumulative penalty function. The method is applied to a
synthetic data set reconstructed from the timescale and rate functions for seven ridges,
derived by Cande & Kent (1992) under the assumption of smooth spreading in the
South Atlantic. We find that only modest changes in the timescale (less than 5 per cent


Source: Acton, Gary - Department of Geology, University of California, Davis


Collections: Geosciences