Note on the natural remanent magnetizations of dirt-ice layers collected from the bare ice field in East Antarctica

Abstract

Natural remanent magnetizations (NRMs) of 5 dirt-ice layers including tephra collected from the Allan Hills in Southern Victoria Land, the Yamato Mountains and the Sφr Rondane Mountains in Eastern Queen Maud Land, East Antarctica, were investigated. The NRMs with 1.38 to 22.1×(10)^Am^2/kg in intensity were very stable against AF demagnetization at least up to 50mT. The magnetic layers consisted with the dirt-ice layers recognized by the naked eye, but magnetizations in the clear-ice were weak for any significant measurements. The uniform NRM directions were obtained in the dirt-ice layers with upward directions. Those of the oriented 2 samples (A, E) were almost parallel to the present geomagnetic field direction in situ. So, a possible mechanism is rearrangement of the magnetic grains adjusting the NRM directions to the geomagnetic field direction due to partial melting of the ice around the grains by the solar radiation.