A TEST OF THE GAD HYPOTHESIS OVER THE PLIO-PLEISTOCENE WITH PALEOMAGNETIC RESULTS FROM ANTARCTICA AND THE GOLAN HEIGHTS, ISRAEL

The geocentric axial dipole (GAD) hypothesis states that the geomagnetic field may be approximated by a dipole that is positioned in the center of the Earth and aligned along the spin axis. We examine this hypothesis over the Plio-Pleistocene with paleomagnetic results from Antarctica (78° S, 167° E) and the Golan Heights, Israel (33.1° N, 35.8° E). Paleodirection was determined from AF-demagnetization and thermal demagnetization experiments. Ninety-eight sites from Antarctica yield a paleopole at 87.6° , 201.8° (α₉₅ = 5.5°) and 44 sites from the Golan Heights find a paleopole at 86.3°, 120.8° ( α₉₅ = 4.4°) (Behar et al. 2019). Both paleopoles are consistent with a geocentric axial dipole field. An IZZI-modified Thellier-Thellier experiment was applied to recover paleointensity. The quality paleointensity results were selected after subjecting the measurements to a set of strict selection criteria (Cromwell et al. 2015). Twenty-eight sites from Antarctica recover a 43.4 ZAm² Paleomagnetic Dipole Moment (PDM), while 16 sites from the Golan Heights recover a 64.6 ZAm² PDM. The two PDMs are inconsistent with a GAD field. The stronger PDM measured in the Golan Heights is in agreement with a similar paleointensity study conducted in Iceland (64.36° N) (Cromwell et al. 2015). We subjected their data to the same set of quality criteria and found that fifty-six sites pass our selection criteria and recover a 59.9 ZAm² PDM. The stronger PDM observed in the Golan Heights and Iceland may reflect a hemispheric asymmetry in the intensity of the average paleomagnetic field. Alternatively, the weaker PDM in Antarctica may indicate a regional anomaly in the field near the Erebus Volcanic Province, Antarctica.