Geocentric Axial Dipole Hypothesis: A Least Squares Perspective

摘要: Departures from the geocentric axial dipole (GAD) model of time-averaged paleomagnetic field have been proposed both for time-interval 0-5 Ma and Mesozoic Paleozoic. At present basic problem is that there are not enough data sufficient quality to be able determine second order terms other than a small persistent quadrupole (GAQ). Even interval using lava flow database, majority were derived around 25 years ago when demagnetization analytical procedures as robust those currently in use. There many ways which an artificial octupole (GAO) term can arise artifacts these discussed some detail least squares approach. No differences between normal reverse fields seen data. Application random paleogeography test suggests GAO Mesozoic, Paleozoic Precambrian. However it has now shown method flawed because assumption valid. It reconstruction Pangea (Pangea A versus B) during early resolved if present. However, used this conclusion 1970s need redone modern methods. only distinguishable feature GAQ about 4% GAD field.