Paleomagnetic investigation of Ferrar dolerite in the McMurdo Sound region, Antarctica

Abstract

Paleomagnetic samples were collected from a sill and dykes of Ferrar dolerite of the Jurassic age in the Wright Valley, the Allan Hills, the Carapace Nunatak and Mt. Fleming of the McMurdo Sound region. The stability of the natural remanent magnetization (NRM) of these samples was tested against the alternating field (AF) and thermal demagnetization, and the hysteresis and thermomagnetic properties were also measured. The overall results show that the samples from the Wright Valley, the Allan Hills and Mt. Fleming have a reasonably stable NRM; the samples from the Carapace Nunatak were less stable. The NRM carriers are inferred to have a pseudosingle or multi domain structure for the samples from Carapace Nunatak and a single or pseudosingle domain structure for others. All these samples were magnetized to the normal polarity, and the calculated VGP positions were 45.3°S・152.0°W for the Wright Valley, 47.0°S・133.2°W for the Allan Hills and 68.6°S・139.5°W for Mt. Fleming. The virtual geomagnetic pole (VGP) positions obtained in this study are in reasonable agreement with other Jurassic VGPs from Antarctica. The mean VGP center obtained from three values in this study, excluding that of the Carapace Nunatak, and from seven values in the previous studies is located at 53.9°S of latitude and 141.8°W of longitude for Ferrar dolerite.