Long Period European Geomagnetic Secular Variation Confirmed

The periodicity of geomagnetic secular declination changes for the last 10 000 yr, first observed from sediments in Lake Windermere, is verified by radiocarbon age determinations from Blelham and Ennerdale lakes in north-west England. No clear correlation of the British records can be made with Continental European data, suggesting that a complex, rather than simple, geographic pattern of long-period secular changes has existed. Geomagnetic declination variations, with several restrictive factors, can be used to date Flandrian sediments. It has recently been suggested that geomagnetic inclination and NRM intensity of the Lake Windermere record can be used for dating with an accuracy approaching ±200 years. Palaeomagnetic measurements on additional cores from Lakes Ennerdale and Blelham, north-west England and Lough Neagh, Northern Ireland, chemical and mineral magnetism analyses and basic geological principles show that these two magnetic parameters cannot reliably supply dates of the accuracy which can be derived from geomagnetic declination variations.