Date: Wednesday July 14, 2021 at 4:00 PM EST
Title: Rock Magnetic Properties: Why bother??The Storyline Linking rock magnetism, paleomagnetism and magnetic models
Speaker: Bill Morris, Professor Emeritus, McMaster University.
Location: Register here
Central to the interpretation of all magnetic anomaly data sets is an understanding of the physical properties of the rocks that are controlling the observed signal. All rocks have contributions from three types of magnetic signal: induced, viscous and remanent. The magnitude of these contributions, changes from rock to rock. In this presentation I will present examples of the measurement and significance of each of these contributions to observed magnetic anomalies. For induced magnetisations I look at various methods of measuring / estimating magnetic susceptibility and consider some of the problems associated with these measurements. For viscous magnetisations I present examples where one needs to carefully assess the importance of this contribution. For remanent magnetisations I discuss the importance of the Koenigsberger ratio, and why it is important to always reference model derived magnetic vector data to tectonic controls provided by reference APWP curves. Finally, I show why borehole magnetics should become as common as airborne magnetic surveys.
Bill started his career in Geology with a B.Sc. Hons degree from the University of Leeds which included his first ground magnetic survey as his Bachelor thesis project. Next Bill was one of the first Open University PhD graduates in 1974 with a Life and Earth Sciences PhD entitled “Palaeomagnetic studies in the British Caledonides”. Bill started a post-doctorate appointment in Canada at the University of Western Ontario, before completing his PhD. He had to fly back for his thesis defense! After moving to Ottawa to do a post-doctorate appointment with the Earth Physics Branch of EMR, Morris Magnetics was formed to do paleomagnetic studies in the Sudbury Basin and rock magnetic studies at various possible Radwaste sites. He has remained in Canada ever since, finding his niche at McMaster University in Hamilton, Ontario in 1989. He started as an Associate Professor in the Department of Geology making his way up to Chair of the department in 1994 and became a Professor of Geography and Earth Sciences in 1998. Over the many years at McMaster Bill supervised several students who are now leading scientists in the application of magnetic surveys. Retiring from McMaster in 2015 he is today, an Emeritus Professor of Geography and Earth Sciences. He continues to write journal articles on physical rock properties, borehole magnetics and more recently tensor magnetics.