HR: 16:05h
AN: GP14A-01 INVITED     [Abstracts]
TI: Bullard Lecture: the Recording of the Ancient Geomagnetic Field
AU: * Langereis, C G
EM: langer@geo.uu.nl
AF: Paleomagnetic Laboratory Fort Hoofddijk, Dept. of Earth Sciences Utrecht University Budapestlaan 17, Utrecht, 3584 CD Netherlands
AB: Modern observatory and satellite data yield a detailed picture of the recent geomagnetic field, a timespan , however, that is still too short to characterise field behaviour and the influence of deep Earth processes over typical core and mantle time scales. Therefore, we require observations from the ancient field through paleomagnetism, i.e. the recording of the ancient field in rocks of any age and over any timespan. In paleomagnetism, there are two critical criteria that determine the success of using ancient records: the accuracy of dating the rocks and the reliability of the rock as a recording medium. For typical paleomagnetic purposes, e.g. global tectonics or magnetostratigraphic dating, the criteria may seem less stringent than for recording typical geomagnetic field behaviour. Also paleomagnetic applications, however, still require considerable improvement, since many existing and especially - but not solely - older records lack the currently required reliability. With increasing precision and resolution requirements, e.g. for high-resolution paleosecular variation studies, the recording reliability of rocks seems to reach its limit. There is hope, however, and modern developments in technology, methodology and statistical models show that considerable improvement of extracting the ancient signal is possible. I will discuss the pitfalls of recording the ancient signal, its use for paleomagnetic and geomagnetic purposes, and give a (bright ?) outlook for the future.
DE: 1500 GEOMAGNETISM AND PALEOMAGNETISM
SC: Geomagnetism and Paleomagnetism [GP]
MN: Fall Meeting 2005