Detransformation of the British geomagnetic secular variation record for Holocene times

摘要: In this note we replot the British post-glacial secular variation curve in terms of actual values declination and inclination, rather than ‘transformed’ inclination system used our original paper (Turner & Thompson 1981). This should facilitate comparison record with contemporaneous European archaeomagnetic data. Our composite was obtained by averaging dated records from 10 cores lake sediment. The sequence unit vectors describing magnetic direction each core rotated so as to place its mean (the over section between 0 7000 BP, time span shortest core) at zero transformed (dT = O”, IT 0”). coordinate frame is thus derived direction, assumed represent geomagnetic field yr period, tube orientation during coring. Hence problem not knowing azimuthal corer collection avoided, can be averaged system. Transformed coordinates then, provide a convenient, generalised method plotting sediment records. However, method, sample straightforward, results readily plotted absolute values. So for consistency when comparing two, have attempted here ‘detransform’ record. following procedures, assumptions approximations were taken produce detransformed magnetograms Bauer-type plots Figs 1 2. (1) Amplitude correction. Although combination data sets produces good estimate signature variations, factors contribute an overall loss amplitude both inclination. (a) quality recording varies widely different sediments, depending on porosity sediment, size shape distributions nature carrier (Verosub 1979). Loch Lomond sediments carry good, high pattern remanent directions, which most recent closely follow London observatory much wetter less compacted Llyn Geirionydd,