Measurements of the Natural Remanent Magnetism and Anisotropy of Susceptibility of some Swedish Glacial Silts

Summary. This paper describes the results of measurements of the magnetic remanence and anisotropy of susceptibility of some Swedish varved silts. An attempt has been made to observe in nature the effects, which have been demonstrated in the laboratory, of water currents on these properties and to obtain new data on the effects of slopes on the direction of remanence.
It was not possible to obtain quantitative confirmation of the effects of water currents though it is shown that the field results fit qualitatively with those from the laboratory and that the effects of currents may in favourable circumstances be neglected or corrected for. By combining the new data on the effects of slopes with those previously published it has been found possible to demonstrate the importance of grain size in determining the magnitude of the bedding error correction and an expression has been found which gives this correction to an accuracy comparable with the error of measurement of remanence direction.
It is concluded that, since all known systematic deviations of the remanence direction may now be corrected for, it should be possible, in suitable circumstances, to obtain reliable estimates of field directions over the last 10,000 years from measurements on the Swedish varves.     

Remanent magnetization of Precambrian and Cretaceous kimberlites in South Africa

Summary. Middle Precambrian and Cretaceous kimberlites were collected from three sites (Premier, Montrose and National) and two sites (Wesselton and Koffyfontein) in South Africa respectively. The natural remanent magnetization of these rocks remains stable to both alternating field and thermal demagnetization. The virtual geomagnetic pole-positions derived from the directions of stable remanence of the Precambrian rocks can be correlated with palaeomagnetic poles obtained from other Middle-Late Precambrian rocks in Africa. The Cretaceous poles for the Wesselton and the Koffyfontein rocks coincide with other Cretaceous poles.