Postęp w badaniach utworów paleozoiku prowadzonych przez Instytut Geologiczny metodami geofizycznymi

Abstract

 Po przedstawieniu historii badań geofizycznych omówiono rozwój metodyki badań skonsolidowanego podłoża w Polsce oraz ostatnie prace syntetyczne, których wyniki ujmuje mapa morfologii i rejonizacji. Podano przebieg i wyniki badań regionalnych utworów paleozoicznych, prowadzonych pod kątem poszukiwań złóż ropy naftowej i gazu ziemnego. Zreferowano także prace geofizyczne, wykonywane dla celów poszukiwań złóż surowców mineralnych stałych. Na koniec podano główne kierunki badań geofizycznych, przewidywanych na najbliższe lata. THE PROGRESS IN STUDIES ON PALEOZOIC ROCKS BY MEANS OF GEOPHYSICAL METHODS IN THE GEOLOGICAL INSTITUTE The first part of the paper deals with the beginnings of geophysical studies in Poland and their subsequent development.In part dealing with studies on consolidated basement, there are discussed developments in methods of measurement and interpretation, mainly with reference to seismic refraction. The refraction, when combined with magnetic, gravimetric and magnetotelluric surveys, made it possible to trace morphology and extent of crystalline basement in the Precambrian Platform, large blocks of Baikalian basement in south-eastern Poland, the Upper Silesian Coal Basin and neighbouring part of the Carpathians, and consolidated basement of the Paleozoic Platform. The results of these studies were presented in the form of maps in the scales 1:500 000 and 1:2 500 000 (Fig. 1). The maps show some areas requiring further geophysical studies for solving a number of still open questions. This is especially the case on the contact of the Precambrian, and Paleozoic Platforms and the Carpathians.In discussing geophysical surveys of the regional type, attention is paid to methodology of works, changing from oscillographic recording to magnetic (in 1968) and finally numerical recording (in the seventies) in the case of the seismic method. The developments in techniques and methodology essentially influenced the quality of the obtained data, especially in continuity of traced horizons and downward range of observations. Reliable seismic boundaries from rocks underlaying the Zechstein began to be recorded in the years 1976–1978. Attention is drawn to the results of surveys along regional profiles cutting the area of Poland from SW to NE, made in the years 1973–1976. Using gravimetric, magnetic, geothermal, geoelectric and seismic methods, a complex interpretation could be performed (Fig. 2).The range and results of surface geophysical surveys of the areas of western Pomerania, Gopło Pabianice and the Warsaw Basin (Fig. 3) are given. In these areas, morphology of top surface of theZechstein has been traced.In discussing magnetic and gravimetric surveys, references are made to the results of elaboration of uniform maps for the whole area of Poland in the scales 1:500 000 and 1:200 000. Some remarks are given on directions in interpretation aimed at tracing reservoir horizons and estimating their parameters in well logging, as well as on the extent and results of surveys in the Baltic Sea.In discussing regional surveys, a necessity of further geophysical studies of areas with insufficient knowledge of sub-Zechstein and Lower Paleozoic tocks is emphasized.The seventies witnessed rapid developments in techniques and methodology of geophysical surveys aimed at search and recognition of deposits of solid mineral raw materials. Magnetic, gravimetric and geoelectric surveys were intensified and new methods were put into practice, e.g. mercurometry, gamma radiation spectrometry and geothermics. Moreover, the range of use of seismic methods in structural studies became markedly widened.The geophysical surveys were concentrated in the following regions:1 – The Sudety Mts and Fore-Sudetic Block. Semidetailed magnetic and .gravimetric mapping has been completed, similarly as aeromagnetic mapping, and complex interpretation of all the geophysical data started (Fig. 4). Numerous measurements were taken for the needs of structural, deposit and mapping works.2 – The Upper Silesian Coal Basin and its north-eastern margin. Seismic surveys aimed at recognition of structure of Carboniferous and Devonian rocks of this area and complex interpretation of gravimetric and magnetic data have been completed. The structure of Paleozoic rocks was studied with the use of a set of geophysical methods at the margin of the Basin (Fig, 5).3 – Góry Świętokrzyskie Mts. Gravimetric, geoelectric and magnetic surveys were mainly concentrated in north-western part of this region. They were aimed at reconstruction of structure of Devonian, Zechstein and Triassic rocks from the point of view of estimation of deposit perspectives.The directions of further geophysical surveys are also discussed. In accordance with the program of intensification, the surveys will be aimed at search for sources of energy (coal, gas, radioactive elements) and building materials and solving some problems of hydrogeology and mapping. The demand of national economy for metal ores and non-metallic raw materials also can for continuation of wide-range prospecting.