Fifty Years of Palaeomagnetic Studies in the Institute of Geophysics, Polish Academy of Sciences

Abstract

Palaeo- and archaeomagnetic investigations in the Institute of Geophysics were initiated at the beginning of 1960s. The archaeomagnetic study was performed in the Geomagnetic Observatory in Hel till the mid-1980s and was resumed lately in the Warsaw laboratory. Palaeomagnetic study begun in 1963 but the palaeomagnetic group obtained necessary place for the laboratory in the Central Geophysical Observatory in the newly finished building in Belsk later in 1966. Formally, the Paleomagnetic Laboratory was established in 1972. From the very beginning, palaeomagnetic studies were accompanied by studies of magnetic properties of rocks and minerals-carriers of natural remanence and by measurements of magnetic susceptibility and its anisotropy. Therefore, the laboratory became successively equipped with the apparatus for strictly palaeomagnetic study (astatic and spinner magnetometers and demagnetizing devices) as well as with devices for rock-magnetic investigations (apparatus for thermoanalysis, system for measuring of hysteresis parameters and for study of magnetic remanence at low temperatures, torsion balance, device for study of magnetic properties under mechanical stress and temperature, device for study of alterations of magnetic minerals based on thermally stimulated emission of exo-electrons (TSEE). The last three devices have not been in use for several years. At the end of 1980s, the Institute moved to a new building and the whole laboratory was moved to Warsaw. Moving palaeomagnetic measurements to town was possible due to the replacement of spinner magnetometer by the cryogenic magnetometer SQUID, which is much more sensitive and less affected by the urban disturbances. Computer software packages that are written in the Institute or obtained from their inventors became a great help in the interpretation of experimental results. Palaeomagnetic investigations have been performed in our laboratory on rocks of various origins and age, coming from various regions of Poland and other countries often in cooperation with scientists from foreign laboratories. Numerous palaeomagnetic results that are obtained in our laboratory are in the world data palaeomagnetic basis and on Apparent Polar Wander Paths constructed for various regions. Study of anisotropy of magnetic susceptibility brought interesting results concerning problems of tectonics; study of rock-magnetic properties helped to identify carriers of primary and secondary components of natural magnetic remanence in many cases. In the last 10 years, a group in our laboratory has been studying very important problems connected with environmental magnetism by applying of magnetometric methods for investigations of soil and air pollution.