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1 School of Earth Sciences, The University of Birmingham, Birmingham B15 2TT, UK
2 TERRASCIENCES Ltd, 8 Canfield Place, London NW6 3BT, UK
Although the study of magnetism is one of the oldest sciences, palaeomagnetism is a relatively young geoscience which incorporates aspects of geomagnetism, rock magnetism and geology. Its application to sedimentary sequences developed rapidly in the post-war era as a result of both theoretical and technological advances. The theoretical advances included an ever-increasing understanding of the Earth’s magnetic field and a much more detailed knowledge of the physical properties of those minerals capable of carrying magnetism (natural remanence) under Earth surface conditions. Also, applications to a wide variety of geological problems in many different parts of the world led rapidly to a much greater awareness of the way in which rocks acquired their magnetization, how it might be altered during later geological history and how the derived palaeomagnetic directions might be used to unravel the movement of large crustal blocks (apparent polar wandering) and the more localized rotation of smaller tectonic blocks. A key phase in the development of palaeomagnetism was the recognition that marine magnetic anomalies represented reversals of the Earth’s magnetic field. Subsequent systematic sampling and measurement of the ocean basins by the ODP (ocean drilling project) has resulted in a sophisticated geomagnetic polarity time scale (GPTS) from the middle Jurassic to present day.
It is beyond the scope of this overview to provide more ground rmation but there are a number of excellent texts which cover all aspects of palaeomagnetic theory and application. For theoretical background there is a thorough introduction to geomagnetism by Parkinson (1983); O’Reilly (1984)
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