报告题目：The Dynamic Geomagnetic Field Revealed From Scientific Ocean Drilling
报告人：Gary Acton 教授 （Sam Houston State University）
Ph.D.(Geophysics), Northwestern University,1990； M.S.
(Geophysics), University of Arizona,Tucson,1986B.S.
(Geology), Indiana University, Bloomington
Marine Geology and Geophysics, Scientific Ocean Drilling, Chronostratigraphy,
Plate Tectonics, Geodynamics, Paleomagnetism, Geomagnetism, Paleoclimatology,
Exploration Geophysics, and Data Analysis
Dr. Acton has sailed as a paleomagnetist, stratigraphic correlator, and staff scientist on 10 ocean drilling expeditions that have cored in diverse settings from Antarctica to the Arctic and from the margins of Spain and Portugal to the Japan Trench. He has published 117 articles and books, 21 open-access reports, one proprietary book for industry, and many scientific meeting abstracts. He was selected as one of The Ocean Distinguished Lecturers for the 2014-2015 academic year.
In this talk, Dr. Acton will tell us how paleomagnetic signal recorded in the sediment and basalt from the drill cores can provide a means of determining the position of the plate relative to the spin axis which gives the latitude of the lithospheric plates through time, and how scientific ocean drilling helped to reveal the dynamics of the geomagnetic field. Similar to an array of geomagnetic stations that record variations in the direction and strength of the geomagnetic field over modern times, marine sediments record the ancient geomagnetic field. The resolution of that record is largely controlled by the sedimentation rate, in which thick sedimentary sections deposited at high sedimentation rates give long continuous records that can reveal both long and very short-term changes in the field. Ocean drilling has selectively targeted these sedimentary sections at many sites around the globe, providing essentially a constellation of paleomagnetic stations. Rather than a fairly stable field punctuated only by the randomly occurring geomagnetic reversals, the paleomagnetic data from these sites show continual dynamic variations in both the direction and magnitude of the geomagnetic field. These are accentuated by even more complex changes during reversals and numerous geomagnetic excursions, which may not occur randomly in time and which reveal clues about deep Earth processes.