Regional analysis and mapping of various geophysical data has been recognized as an important — even crucial — element of geological studies for many years. Due to rapid development of advanced numerical tools it is presently possible to construct, maintain and comprehensively analyse even very large geo-databases, including seismic, gravity, magnetic, geothermal and other geophysical data. In many countries, national geo- logical surveys, commercial companies and research institutions are involved in mapping projects focused on spatial representation of geophysical data that could later be used for various studies. Recently, new policy of the Polish Ministry of Environment regarding geological cartography in years 2005-2020 has been declared (cf. Ber & Jezierski, 2004). In this document, geological cartography is used as a rather wide term that includes also other geo-disciplines like geoenvironmental studies or surface geochemistry. Among them, mapping of geophysical data is also mentioned. In this paper, short overview of the current state-of-the-art of selected aspects of regional geophysical mapping in Poland is given, with some remarks regarding potential directions of future work.
Normal 0 21 false false false MicrosoftInternetExplorer4 The Ludlovian greywackes of the Holy Cross Mountains (HCM) represent a part of the sedimentary cover of the Łysogóry and Małopolska terranes located in the Trans-European Suture Zone, central Poland. The rocks form the sedimentary infill of the Caledonian foreland basin that developed at the Tornquist margin of Laurussia and had source-areas located on the orogen side of the basin. Until the present, the source terrane of the basin has not been identified in its potential location – at the south-west margin of the East European Platform. The Ludlovian greywackes of both parts of the HCM show a lot of similarities in clast spectrum, timing, and geochemical features, which implies similar sources of the clastic material. The petrographic modal composition and geochemical features indicate recycled orogen signatures with a distinct undissected, evolved magmatic arc component. The latter is particularly evident from the extraclast spectrum that contains andesite, trachyte and dacite clasts. Beside the volcanic rocks, the source area consisted of sedimentary and metasedimentary rocks with high amounts of cherts. The geochemical and petrological features in the rock succession point to an evolution of the tectonic setting from an active to a more passive margin type indicating synorogenic formation of the studied rocks. Based on the rock record, we suggest that the Upper Silurian greywackes originated as a result of the collision of the Tornquist margin of Laurussia with a volcanic arc (here: the Teisseyre Arc) – located probably at the easternmost extent of the Avalonian Plate. In this scenario, the arc-continent orogen was composed of an uplifted filling of the forearc basin, an accretionary prism, volcanic arc rocks, and an exhumed foreland basement - analogously to the present-day Taiwan orogen. The second key issue is the palaeogeographical relation between the Małopolska (Kielce Region) and the Łysogóry terranes in the Late Silurian. Despite the analogous grain composition and clast types, the Łysogóry Region greywackes are composed of distinctly more altered detritus, which is in accordance with the more distal character of the Łysogóry Basin. The latter is manifested, e.g., in the lack of Caledonian deformations. The present-day adjacency of both domains containing correlative greywacke formations coupled with contrasting alteration and Late Silurian transport directions parallel to the terrane boundary imply small to medium-scale (below palaeomagnetic resolution) left-lateral movements of the Małopolska and Łysogóry crustal blocks along the Holy Cross Fault in post-Silurian times.
Abstract: A range of mafic to intermediate extrusive and intrusive igneous rocks from the central part of King George Island were sampled for isotopic and palaeomagnetic studies. Single-grain U–Pb dating of zircon from basalts to trachytes from the upper part of the section gave Eocene ages (53.0 ± 0.7 to 47.8 ± 0.5 Ma), consistent with a whole-rock 40 Ar– 39 Ar age of 52.7 ± 0.6 Ma. These ages correspond to the first stages of the opening of the Drake Passage. A Late Cretaceous 40 Ar– 39 Ar age (75.4 ± 0.9 Ma) was obtained only from one basalt sample from the bottom part of the section (Uchatka Point Formation). These new age determinations change substantially the existing stratigraphic chart of King George Island. Palaeomagnetic poles show a marked departure from the East Antarctic apparent polar wander path, reflecting anticlockwise rotation of the rocks after the Early Eocene. The mean age of zircon grains from a basaltic lava flow overlying the tillite at Hervé Cove (48.9 ± 0.7 Ma) and the normal polarity magnetization of surrounding basalts allow correlation of the tillite with the upper part of the C22 polarity chron (49.4–48.6 Ma). The consistency in age, crystal morphology, and U and Th contents strongly suggests that the zircon records the magmatic event. However, derivation of the zircon from an older magma and a slightly younger age for the tillite cannot be totally excluded.
New 40 Ar- 39 Ar isotope ages of mafic and felsic rocks from the contact zone of the Malopolska and Brunovistulian terranes are presented and discussed. A 40 Ar- 39 Ar age estimation of detrital muscovite from a Lower Devonian old red type sandstone drilled on the Malopolska side of this zone was also done. Our studies reveal that three events of Paleozoic magmatic activity took place in the study area. The oldest, late Emsian episode is recorded by a diorite from the core part of an intrusion penetrated by the Sosnowiec IG 1 borehole. A younger, Visean event is documented by a diabase cored in the borehole WB-137. Diabases from Niedwiedzia Gora and from borehole PZ-10, and a rhyodacite from borehole 16-WB gave early Permian (Artinskian-early Sakmarian) ages. The youngest, middle Sakmarian age was obtained for a diabase forming the external parts of the Sosnowiec IG 1 polycyclic intrusion. A diorite penetrated by the Sosnowiec IG 1 borehole was emplaced during the late Emsian extension that preceded the Lochkovian-Pragian? transpression related to the final docking and amalgamation of the Brunovistulian Terrane.
<p>The Brno Massif forms a part of larger tectonostratigraphic unit named the Brunovistulian Terrane (BVT) that is one of crustal block of Europe with the Neoproterozic basement. &#160;However, the Neoproterozoic orogenic belt was developed in wide area i.e. along the Gondwana margin and near the present day eastern and southern edge of the East European Craton. For more than 20 years, the problem of primary setting of the BVT inside the Neoproterozic orogenic &#160;belt have been discussed. Also the path of their drift and &#160;time of their final accretion have been a matter of debate. To solve these problems the paleomagnetic and isotope studies of vertical intrusions cutting the BVT basement near Brno in Moravia have been undertaken. Preliminary isotope dating of granitic and basaltic intrusions points to the early Silurian age of them. Results of demagnetization of paleomagnetic samples from three localities revealed the presence of stable components with a steep inclination, at that time characteristic for the northern margin of Gondawana but not for the Baltica paleocontinent that during the Silurian was situated between the equator and 30<sup>o</sup>S. The Emsian &#160;&#8220;old red&#8221; type deposits may indicate that final amalgamation of the BVT took place some-time between the Silurian and the Devonian. This time of joining of the BVT&#160; to Baltica and quite high (50 &#8211; 60<sup>o</sup>S) paleolatitudes obtained from the early Silurian rocks of the Brno Massif&#160; point to a rapid drift of the BVT across the Rheic Ocean during the Silurian.</p>
NEW MIDDLE DEVONIAN PALEOMAGNETIC POLE FROM SIEWIERZ ANTICLINE - THE END OF CONCEPTION OF LARGESCALE STRIKE SLIP MOVEMENTS ALONG SW MARGIN OF THE EAST EUROPEAN PLATFORM DURING VARISCAN TIME!?
Summary
Paleomagnetic pole with very good quality factor (Q = 6) has been reported from Middle Devonian dolomites of NE margin of the Upper Silesian Coal Basin. Positive fold test (Fig. 1 b, 3) shows that the characteristic remanent magnetization was acquired before tectonic deformations. Paleomagnetic pole obtained here is in an excellent agreement with the corresponding Early Devonian poles of Baltica (Table). A conclusion was drawn, that at least since Middle Devonian the Upper Sillesian and Malopolska blocks were situated near their present position.
Studies of the anisotropy of magnetic susceptibility (AMS) were carried out in order to define the directions and strength of palaeowind during the sedimentation of the youngest loesses in Poland and western Ukraine. These sediments, like the Chinese and Alaskan loesses, appear suitable for application of the AMS method. The inclined mean minimum axes were considered as reflecting the prevailing palaeowind direction at the time of loess sedimentation. The majority of the sections studied indicate a palaeowind direction from W-SW to E-NE, with a mean azimuth of 2588. This direction corresponds to the strike of the Weichselian ice-sheet margin and is parallel to the axis of the lowland between the ice-sheet margin to the north and the Carpathian Mountains and the Podole Upland to the south. Further AMS studies of the oldest parts of loess sequences in Poland and western Ukraine may help in reconstruction of the atmospheric circulation in this part of Europe since c. 900 kyr BP.
Recently, M. Lewandowski (1994) has presented a mobilis tic interpretation of my palaeomagnetic data from the Cracow Silesia region (J. Nawrocki, 1993a, b) and even considered them as the next palaeomagnetic evidence for large-scale mobility of the Ma/opolska Block in Variscan time (see also M. Lewandowski, 1993). In fact, that paper has a polemic character and in my opinion ought to be treated as a comment on my interpretations. more so that in my earlier works mobilistic interpretations were presented as well (e.g., J. Nawrocki, 1 992a). The present paper shows that there are no reliable palaeomagnetic arguments for large scale dextral strike-slip displacement of the Malopolska and Upper Silesian Massifs during the Variscan orogeny, and possible smaller-size tectonic rotations (up to 3~') in the syn-Asturian tectonic phase are less probable than a relative stationary model.
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