Analysis of the Thelliers' Method of Paleointensity Determination 2

Applicability to High and Low Magnetic Fields

Abstract

Natural volcanic rock samples which acquired thermoremanent magnetization (TRM) in various laboratory magnetic fields (2-1000μT, or 0.02 to 10 Oe), were subjected to the Thelliers' method to ascertain that small and large paleointensities can be successfully determined experimentally. Results indicate that the Thelliers' method is applicable to a very wide range of magnetic fields, though somewhat smaller values were obtained for very high fields because of the breakdown of the proportionality of TRM to the magnetic field. Experimental errors increase drastically if the magnitudes of the ancient and the laboratory fields differ very much, and the use of matched laboratory field is recommended.
Samples with remanences induced by other methods were also subjected to the Thelliers' method, and some fortuitous results were obtained. Though the Thelliers' method gives reliable results for TRM, care must be employed when the nature of natural remanence is uncertain. Various sources of errors contained in the obtained paleointensity are also discussed.