Budowa podłoża krystalicznego południowego Bałtyku w świetle wyników zdjęcia magnetycznego z lat 1971–1972

Abstract

STRUCTURE OF THE CRYSTALLINE BASEMENT OF THE SOUTHERN BALTIC IN THE LIGHT OF THE RESULTS OF MAGNETIC SURVEY FROM 1971–1972SummaryIn 1971–1972 magnetic measurements were made in a belt of waters measuring 50 sea miles in width and stretching along the southern coast of the Baltic Sea from thePomeranianBayto theBayofGdańsk. This was a common project of theInstituteofGeodesyand Cartography inWarsawand of the Leningrad Branch of theInstituteofEarth Magnetism, Ionosphere and Propagation of Radio Waves at theAcademyofSciencesof theUSSR. In the present article, the authors discuss the extent and methods of magnetic measurements, problems of navigation, the use of deviation and variation corrections and the methods by means of which the results have been analysed. The results of the survey, presented – among others – in the form of contour lines of anomalies of component Z of the intensity of the magnetic field of the Earth, have been used for an analysis of the magnetic picture of the southern part of theBaltic Seaand for its geological interpretation.The depth of the top of the magnetically active basement, corresponding to the top of the crystalline basement, was calculated my means of the tangent method. On this basis a map showing the contour lines of the top of the basement was made (Fig. 1). This map corresponds to the results of refraction measurements made in this part of the Baltic and in the adjacent coastal areas; it also corresponds to the results of studies by D. P. Golub and Y. S. Sidorov (1971). The map also shows the range of granitoids, metamorphic rocks and igneous rocks in the top of the crystalline basement. The range of these rocks, corresponding to the particular types of local magnetic anomalies, was determined by means of the method used by K. Karaczun, S. Kubicki and W. Ryka in the land areas ofPoland. The authors find that as a result of the magnetic survey of the southern part of the Baltic all anomalous elements of the magnetic picture were recorded and some valuable data on the structure of the crystalline basement have also been obtained. A more detailed magnetic survey should be made in the future so that particular magnetic anomalies can be more precisely determined. The kind of apparatuses needed for this purpose should enable the scientists to locate more precisely the particular points of measurements.