The Geomagnetic Field during Palaeozoic Time

摘要: The Palaeozoic reversal sequence is represented by complex rhythms with characteristic times of (5-7)×107, (1-4)×107 and (1-2)×106y. first order units recognized are Arginian (R) 590-535m. y., Siberian (Rn) 535-485m. Baikalian (Nr) 485-430m. Sayanian 430-360m. Donetsk 360-300m. Kiaman 300-240m. Illawarra (NR) 240-215m. y. Three types field transitions have been recognized: 1. “sudden” reversals (single or repeated), 2. a considerable dispersion palaeomagnetic directions, 3. loop-wise rotations the field. latter may result from concurrence axial equatorial dipoles. Reversals usually occur 4 to 10 lower intensity. time span for complete transition ranges 8×103 3×105y. Peculiarities traced over strike distances 1600km. Angular constituents paleosecular variation components (4-8)×103y. 3×104y. characterized standard deviations 6 degrees in stable epochs up 20 intervals frequent reversals.The geocentric dipole good approximation time-averaged However, occasional presence an irreversible dipole, controls shape geomagnetic 3rd type.