ON THE MEASUREMENT OF THE REMANENT MAGNETISM OF LONG CORES

The remanent magnetism of long cores has been determined with a resolution of better 3 cms, using an SCT (Superconducting Technology Inc.) cryogenic magnetometer and a computer deconvolution scheme. The three component magnetometer has a horizontal sample access hole through which the core is passed. The instrument output may be regarded as a convolution of the magnetic fields due to a continuous series of small slices with the waveform representing the response of the instrument to one of the slices. By deconvolution of the instrument output with the system response for the small slice, one obtains an approximation to the point values of magnetization along the core. The method has been checked using a "long core" from the Tatoosh intrusion which had previously been cut into 2 cm sections that measured as individual standard samples on a spinner magnetometer. Ocean sediment cores have also been measured. It appears that the high sensitivity and low drift of the instrument gives effectively noise-free data, which permits useful deconvolution.