EarthRef.org Reference Database (ERR) -- Smith 1967

Smith, P.J. (1967). Estimates of the Devonian geomagnetic field intensity in Scotland. In: U.S. Geological Survey Professional Paper, Report: Geological survey research 1967, Chapter D. U.S. Geological Survey, Reston, VA. 0575-D: D164-D168.

Two hundred and eighty samples from 73 Scottish lower Devonian and Carboniferous basalt lava flows have been investigated to determine the intensity of the ancient geomagnetic field. All but three samples (from two lower Devonian flows) were rejected as unsuitable because of instability of natural remanent magnetization (NRM), alteration in the magnetic minerals during the heating necessary to induce an artificial thermoremanent magnetization (TRM), or remagnetization (probably chemical) since the flows were formed. The samples from the two remaining flows indicated ancient geomagnetic dipole moments of 0.75 and 0.34 X 10 (super 25) gauss cm (super 3) , which are considerably smaller than the present dipole moment (8.0 X 10 (super 25) gauss cm (super 3) ).