Full vector secular variation during the Brunhes Chron in Mexico determined from volcanic hard rocks

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We intend to study systematically volcanic rocks from the Transmexican Volcanic Belt, extending the time range covered in the preceding project back through the entire Brunhes polarity chron (-780 ka). Further palaeomagnetic data shall contribute to increase our knowledge of the variability of the geomagnetic field, including geomagnetic excursions falling into that time window. To recognise such events and excursions, palaeodirections and palaeointensities have been and will be determined. The finding of excursions at low latitudes would be of great interest, to compare the field behaviour with that at high northern and southern latitudes. Some precise age data are already available from Mexican rocks, additional ones will be determined as part of the project. Absolute palaeointensities together with absolute age data will be also of use to refine and calibrate relative palaeointensity curves reported from marine sediments, which may be affected by delayed lock-in of remanence and/or by diagenetic as well as climatic perturbations.