Magnetic Nanopaleontology Helps in Studies of Historical Climate Change

KFU geologists continue their inquiries into lake sediments of Khövsgöl, Mongolia.

Sediments of existing lakes and oceans are basically paleoecological archives of information about climate and various changes that have taken place in the distant past. Climate is the main factor that influences sediment growth in lakes.  Studies of such individual sediment profiles help reconstruct past climate change and thus help make forecasts.

Magnetic-mineralogical research is one of the tools of such reconstruction. One of the most important objects of the research are magnetotactic bacteria (MTB), such as Magnetospirillum gryphiswaldense. MTB are widespread in sediments of fresh water and saline water bodies and in damp soil. During their evolution, they have acquired the ability to navigate in the magnetic field with the help of specific magnetic structures called magnetosomes.

The number of magnetosomes in bacteria varies from 10-20 to about 1,000. Electronic microscopy has helped in finding out that the majority of them are 35 to 120 nanometers in size. Crystals can be shaped like cubes, parallelepipeds, bullets, or even arrowheads. Magnetosomes can be very informative in studies of geomagnetic fields, lithospheric movements, and magnetic field inversions. Biomineralization and genetic studies can also make use of systematic data about them.

At Kazan University, magnetosomes are measured in a coercitive spectrometer, a unique piece of equipment constructed here in the 1980s. Without destroying the sedimental material or separating magnetic structures, the spectrometer can provide data about nanosized magnetic particles of biological origin. Thus, a new discipline emerges, the one that we call magnetic nanopaleontology.

Comparison of existing data with lithological, geochemical and paleobiological research results helps determine the specific changes of the environment that have happened in the past.