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Relative secular variations of the Earth’s magnetic field in the years1966–2016 along the profile across the main tectonic units of Poland (Zgorzelec-Wiżajny profile)

Wojas Anna, Grabowska Teresa

Geology, Geophysics and Environment

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2019

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Vol. 45, no. 3

183--194

EN

The paper summarizes 50 years of research on relative local secular variations of the total magnetic intensity (TMI) along Zgorzelec-Wiżajny profile (Z-W profile) through the years 1966–2016. The Z-W profile (approximately 650 km length) cuts through Europe’s major tectonic units, including a zone of Variscan folds in the Paleozoic platform (PP), the Trans-European Suture Zone (TESZ) and the Polish part of the East European Craton (EEC). Measurements of TMI were made at 31 sites of the profile and reduced to the base recordings at the Central Geophysical Observatory in Belsk. Based on linear approximations of relative geomagnetic field values changes in time, relative annual changes in time (relative secular variations) expressed in nanoteslas [nT] per year were calculated. The study on relative geomagnetic field values revealed slower secular variations of the geomagnetic field in EEC as compared to those in PP and TESZ. However, they show lower amplitudes of these variations. An interesting phenomenon are rapid changes in the time of the relative values (trends) of TMI starting from the year 2000, also expressed as the relative secular variations per year, particularly visible in PP area. In the qualitative sense, relative secular variations show a correlation with the main geological units in the Polish territory and also important elements in the seismic and geothermal model of the lithosphere.

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Paleogene-Neogene tectonic evolution of the lignite-rich Szamotuły Graben

Widera Marek, Stawikowski Wojciech, Uścinowicz Grzegorz

Acta Geologica Polonica

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2019

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Vol. 69, no. 3

387--401

EN

The Szamotuły Graben covers the southernmost part of the Permo-Mesozoic Poznań–Szamotuły Fault Zone. Along this regional discontinuity there are several salt structures, including the Szamotuły diapir, over which an extensional graben formed in the Paleogene and Neogene. The graben is located north of Poznań in central-western Poland, and is NW–SE-trending, ~20 km long, 3–5.5 km wide, and up to 160 m deep. It is filled with Lower Oligocene and Neogene sediments, including relatively thick lignite seams. Data from boreholes allow the assignment of the graben-fill sediments to appropriate lithostratigraphic units. Furthermore, analysis of changes in the thickness of these units provides evidence for periods of accelerated graben subsidence or uplift relative to its flanks. As a result, two distinct stages of tectonic subsidence and one inversion in the Paleogene–Neogene evolution of the Szamotuły Graben have been distinguished. Thus, relatively significant subsidence occurred in the Early Oligocene and the middle Early–earliest Mid-Miocene, while slight inversion took place in the middle part of the Mid-Miocene.

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O nowych rozwiązaniach tektonicznych w „Atlasie geologicznym Polski”

Aleksandrowski P., Mazur S.

Przegląd Geologiczny

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2017

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Vol. 65, nr 12

1499--1510

EN

Authorial comprehensive comments and explanations are given to some of the interpretations applied in the tectonic part of the newly published Geological Atlas of Poland (Nawrocki, Becker, 2017) that considerably change the hitherto generally accepted concepts. It should be, however, admitted that most of those "new’" solutions were already proposed in the past by other workers as hypotheses that could not have been tested in the then state of knowledge on Poland’s deep geology and scientific tools at hand. This has now changed with abundant new data obtained with modern seismic techniques and advanced methods of potential field modelling. Using those data, we justify the reasons for, among others, a significant eastward shifting the front of the Variscan Orogen in Poland andfor the accompanying change in position of the division line between the Precambrian and Palaeozoic platforms. We also show the rationale for accepting a far-reaching southwestward extent of the East European Craton’s crystalline basement below the Palaeozoic Platform and for reinterpretation of the Teisseyre-Tornquist Zone’s nature, together with the question of early Palaeozoic terranes in the TESZ and the situation of the Caledonian foredeep at the SW margin of the East-European Craton.

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Seismic refraction investigations in Poland (1964-1978) and their use in continuing studies

Młynarski S.

Geological Quarterly

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2002

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Vol. 46, No 3

247-254

EN

Seismic refraction investigations, performed in Poland between 1964 and 1978, are reviewed. Examples selected from the many seismic profiles, totalling approximately 15 000 km in length, are shown. The most useful profiles as regards geological interpretation are in the Precambrian Platform and along its southwestern edge. Both the top of the crystalline basement and a system of faults, downfaulting the basement towards the south-west, can be identified in that area. In the Carpathians and its foreland, the top of this basement may be identified together with the bases of thrust flysch nappes. In the Fore-Sudetic Monocline, the top of folded Carboniferous deposits can be determined. The most ambiguous results were obtained from the Palaeozoic Platform.