Mot en ny paradigm i paleomagnetism: Hypotesprovning av en allmänt förekommande biogeokemisk magnetisering av sediment (BRM)
Tidsperiod: 2020-01-01 till 2023-12-31
Projektledare: Ian Snowball
Budget: 3 420 000 SEK
How widespread is biogeochemical remanent magnetization (BRM)? The palaeomagnetic community has, despite cautions, generally ignored the significance of BRM because there is insufficient knowledge about this type of natural remanent magnetization. This PhD project will fill the knowledge gap and construct a diagnostic set of magnetic properties that we will use to test if BRM is ubiquitous. One novel part of the research will be a unique characterization of greigite magnetofossils and their contribution to sediment magnetic properties. Magnetotactic bacteria (MTB), which live in the water column and/or sediments, biosynthesize nanometer-sized single-domain ferromagnetic particles (magnetite or greigite). When these particles become buried in sediments they become magnetofossils and can contribute as a BRM to the NRM that is the basis of all palaeomagnetic studies. We will utilize the fact that single-domain (magnetosomal) particles have fundamentally different magnetic properties compared to larger multi-domain (clastic) particles and systematically measure anisotropy of magnetic susceptibility (AMS) and magnetic remanence of different sediment types to distinguish between depositional and biogeochemical contributions to NRM. Our sources of material will be the natural test beds offered by biogenic-clastic varved lake sediments in Fennoscandia and the Baltic Sea and, in a test of the hypothesis, repositories that contain globally distributed sediments from the oceans.