Fine tuning the radiometrically derived geomagnetic polarity time scale (GPTS) for 0–10 Ma

Abstract

New 40Ar/39Ar step‐heating ages for geomagnetic field reversals at 3.2 and 4.5 Ma, along with previous data at ∼1, 2, 10 and 16 Ma, are used to derive a geomagnetic polarity time scale for 0–10 Ma. These ages for chron boundaries are fitted to the relative widths of the polarity intervals on the ocean floor, using a cubic spline technique. The interpolated ages of chrons for 0–6 Ma are in good agreement with the astronomical time scale and differ considerably from earlier attempts, based, in part, on K‐Ar dates. Significant differences between the interpolated ages and the astronomical time scale are noted for the onset of the Olduvai and Reunion (sub)chrons; there is better agreement if 40Ar/39Ar data obtained from direct dating of these chrons is utilized. This time scale is estimated to be accurate to ±1% for 0–6 Ma; for 6–10 Ma, the lack of a tie‐point limits the accuracy to about ±2%.