Abstract
This work was funded by project CGL2012-32149 (Ministerio de Economia y Competitividad, Spain), projects CGL2011-23755 and CGL2010-14869 (Ministerio de Ciencia e Innovacion, Spain) and the European Regional Development Fund (ERDF). AC acknowledges the support of CONACYT scholarship no. 257639 (Mexico). Technical and human support provided by SGIker (UPV/EHU, MINECO, GV/EJ, ERDF and ESF) is gratefully acknowledged.
Highlights
One of the most relevant variations of the Earth’s magnetic field are polarity transitions, defined as a change of 180◦ in the direction of the dipolar field, globally observed and averaged over a few thousand years (Merrill et al 1996)
Studied flows one sample was selected for these experiments, which included the measurement of strong-field magnetisation versus temperature (MS–T) curves, the determination of hysteresis parameters and the measurement of isothermal remanent magnetisation (IRM) acquisition curves
The DRAT, is the difference between the pTRM check and original thermoremanent magnetization (TRM) value at a given temperature divided by the length of the segment of the Arai plot used for determining the palaeointensity. (vi) Palaeointensity results obtained from NRM–pTRM diagrams must not have a clearly concave up shape, as in such cases remanence is probably related to the presence of MD grains (Levi 1977)
Summary
One of the most relevant variations of the Earth’s magnetic field are polarity transitions, defined as a change of 180◦ in the direction of the dipolar field, globally observed and averaged over a few thousand years (Merrill et al 1996). Few palaeomagnetic and palaeointensity investigations of polarity transitions are focused on the Miocene and older periods. This study is focused on a 9.7 Ma (Glen et al 2003) lava sequence located in La Gomera Island that belongs to the Canarian archipelago. The sequence studied in this work, was partially studied by Glen et al (2003), who reported palaeodirections and palaeointensity results from 22 lavas and interpreted them as recording a geomagnetic excursion (R–T–R). This study is performed in the same sequence, in order to study the complete palaeomagnetic record involving several lava flows immediately below Glen et al.’s (2003) original profile (Fig. 1) and try to discern between the occurrence of a polarity transition or an excursion
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