High absolute paleointensity during a mid Miocene excursion of the Earth's magnetic field

A record of an excursion of the Earth's magnetic field was found in a similar to 14.3 Myr old lava sequence of the shield basalts from Gran Canaria (Canary Islands). The thermal and alternating field demagnetization of the samples from 14 subsequent lava flows revealed mainly single component magnetizations and sometimes minor viscous overprints. Four consecutive flows showed intermediate paleodirections which represent an excursion of the virtual geomagnetic pole (VGP) from the South pole towards the equator in the central Atlantic, Rock magnetic and microscopic analysis revealed high temperature oxidized titanomagnetites as the dominant carrier of remanence. On the basis of reversibility of thermomagnetic curves and limited variation of susceptibility during thermal demagnetization, we selected suitable samples for three slightly different Thellier-type paleointensity methods. The results show a minimum in paleointensity after the directional excursion with intensity values of similar to9 muT. With the pole approaching the equator, values of similar to 27 muT are reached. The intensity at the beginning and at the end of the section is similar to 20 muT corresponding to a virtual dipole moment (VDM) of 6 x 10(22) Am-2. The high intensities during the VGP excursion with a pole near the equator are explained by the same VDM. (C) 2000 Elsevier Science B.V. All rights reserved.