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EN
The results of palaeomagnetic, rock magnetic, and microscopic study of Early Paleozoic metabasites and granulites from the Orlica Śnieżnik Dome (OSD, Sudetes) have been combined with geochronological data. In the eastern part of the OSD (Śnieżnik Massif, SM) ferrimagnetic pyrrhotite is prevalent, accompanied by various amounts of Fe-oxides. In the western part of the OSD (Orlica-Bystrzyca Massif, OBM) Fe-oxides dominate. All magnetic minerals originated during hydrothermal and weathering processes. The palaeomagnetic study revealed the presence of three secondary components of natural remanence: Late Carboniferous, Late Permian, and Mesozoic. Two Paleozoic components are related to volcanic activity in the Sudetes. They are carried by pyrrhotite and Fe-oxides and were isolated only in SM rocks. The Mesozoic component was determined in both parts of the OSD and is carried by Fe-oxides. It covers a time span, from ~160 to ~40 Ma, corresponding to a long period of alteration.
EN
Paleomagnetic studies of Devonian carbonate rocks in the southern Holy Cross Mountains have been conducted, the general aim being to verify the occurrence of hypothetical pre-Variscan rotations of the Małopolska Massif as well as to examine time-relationships between remagnetizations and successive stages in tectonic deformations. The paleomagnetic analysis confirms the presence of the three components of characteristic remnant magnetization. Two magnetite-bearing components display reversed (component A) and normal (component B) polarity. The third component (C) is recorded on hematite and shows reversed polarity. Component B is of synfolding origin and has been recorded during the Visean, whereas components A and C are of postfolding origin and represent Early Permian and Permo-Triassic overprints. These results confirm the stable position of the Małopolska Massif with respect to the East European craton, at least since the Visean. Results of fold tests imply that the earliest phases of Variscan deformation can be dated most probably as Visean, while formation of the main Variscan fold structures was completed during the Early Permian. It is also documented that representative Variscan folds did not significantly change their geometry during Maastrichtian-Paleocene reactivation.
EN
The single-grain U-Pb dating of most zircon grains separated from the Zalas rhyodacites gave mean age of the magma emplacement 294.2 š 2.1 Ma. Some zircons, however, displayed younger ages (268.7š 3.4 Ma), probably related to metasomatic alterations of these rocks. The paleomagnetic ages of the Zalas intrusion and its metasomatosis are slightly younger. It is probably connected with a certain error of time calibration of the reference apparent polar wander path used for paleomagnetic dating.
EN
The paper presents the results of experimental rock-magnetic, paleomagnetic and palynologic study of Paleolithic sediments sampled along two profiles in the Akhshtyrskaya cave, situated in the vicinity of Black Sea shore. In the upper part of profiles, some magnetite was observed; in the middle and lower parts, strongly oxidized non-stoichiometric magnetite and hematite prevail. Thin maghemite covers on the surface of fine magnetite grains are present in the majority of specimens. Natural remanence has one characteristic component (CHRM), mostly of chemical origin, although in few specimens containing magnetite it may be sedimentary. Directions of CHRM obtained by standard paleomagnetic methods revealed anomalous pattern only in layer 3/2, which is slightly older than the overlying layer 3/1 whose age was established as (35š2)×103 years BP by the U-Th method. This suggests that this paleomagnetic anomaly (PMA) can be correlated with Kargapolovo excursion dated on about (45-39)×103 years BP. In the remaining overlying and underlying layers, directions of CHRM are grouped around the present geomagnetic field. Depth distributions of scalar magnetic parameters generally coincide with the lithological division of the profiles. Palynologic study revealed the presence of 22 pollen zones. Five thermomers separated with colder periods were found in the middle and lower parts of profile. The non-magnetite composition of magnetic fraction of the majority of studied sediments – oxidized nonstoichiometric magnetite and hematite – resulted in the lack of correlations between paleoclimatic and scalar magnetic characteristics.
EN
Paleomagnetic and petrological analyses were performed on Devonian carbonate rocks from the Kielce region (Janczyce 1 borehole, Dule, Łagowica escarpment, Budy Quarry) in the Holy Cross Mts. Rock samples were selected from localities with different degree of thermal alteration, diversified lithology and stratigraphy. Investigated carbonates, excluding those from the Budy Quarry, revealed traces of the Early Permian remagnetization related to magnetite. The intensity of the Late Variscan remagnetization is linked to rocks affected by the second stage of dolomitization with increased thermal maturity in the northern part of the Kielce region. The magnetic signal is probably related to rocks’self-cooling, fixed as a result of the latest Carboniferous to Early Permian uplift.
6
Content available remote On the palaeomagnetic age of the Zalas laccolith : (southern Poland)
EN
An age estimation for the Zalas laccolith (Kraków area, South Poland) using the palaeomagnetic method is presented. 29 hand samples were taken from the rhyodacites and neighbouring Visean sediments cropping out in three localities. Two components of magnetization were isolated in the volcanic rocks and Visean sediments. The "A" component, common to the greenish rhyodacites and Visean sediments from Orlej, is carried by magnetite and is regarded as primary. Comparison of the mean inclination of this component with the expected (reference) stable European inclinations leads to the conclusion that the Zalas laccolith was emplaced about 280 Ma ago. The second component, "B", characteristic of the reddish rhyodacites, is carried by hematite and was recorded during the Late Permian (c. 260 Ma) metasomatic alterations of these rocks.The palaeomagnetic poles calculated for the "A" component show a distinct departure from the Permian segment of the Baltic apparent polar wander path (APWP) due to anticlockwise block rotations of the rocks studied that were most probably connected with the Early Permian sinistral transtensional tectonic regime in Central Europe.
PL
Badania paleomagnetyczne 9 fragmentów rdzeni węglanów środkowo- i górnodewońskich pochodzących z Lubelszczyzny (otwory Giełczew PIG 5 i 6) i Górnego Śląska (otwór Goczałkowice IG 1) wykazały obecność wczesnopermskiego przemagnesowania, opartego na magnetycie. W Giełczwi intensywność przemagnesowania wykazuje korelacje z przejawami późnej dolomityzacji, natomiast w Goczałkowicach ze zjawiskami utleniania pirytu. Przemagnesowania są czasowo i, być może, genetycznie związane ze zwiększonym strumieniem cieplnym, wulkanizmem i migracją gorących roztworów we wczesnym permie.
EN
Paleomagnetic investigations of 9 bore core fragments of Middle and Upper Devonian carbonates from theLublin (boreholes Giełczew PIG 5 and 6) and Upper Silesia region (borehole Goczałkowice IG I) revealed the presence of the Early Permian remagnetization related to magnetite. The intensity of remagnetization correlates either with late dolomitization (Giełczew) or oxidation ofpyrite (Goczałkowice). The remagnetization is temporally and probably genetically linked to an increased heat flow, volcanism and hot fluid migration in the Early Permian.
EN
The opposite trend between the contents of garnets and quantity of sulphides and organic matter was stated within Quaternary proglacial deposits in the Łomża region and Kurpie plain of NE Poland, as well as in certain Tertiary sediments. Diagenesis of the discussed deposits yielded new mineral assemblages, which changed chemical and physical characteristics of primary sediments. Such transformations, if not recognized properly, may lead to erroneous conclusions on the type of facies, in stratigraphy based on mineral assemblages, paleomagnetic considerations and paleogeographic interpretations.
EN
Geomagnetic variations in direction as well as in intensity throughout the geologic history as documented in the remanent magnetization of sediment successions generally offer a potential (the investigations are performed in correlation) for dating of these sediments. Therefore, magnetostratigraphic investigations are performed in order to monitor geomagnetic fluctuations and to correlate them to established reference datasets such as the geomagnetic polarity time scale. The last major reversal of the earth’s magnetic field occured at about 780 ka. Since then, a quite large number of so-called reversal excursions with a duration of a few thousand years interrupted the normal polarity phase of the geomagnetic field, known as the ’Brunhes Chron’, about each 50 to 100 kyr. According to absolute as well as relative paleointensity determinations the field intensity throughout the Brunhes Chron was not constant but variable at least within the range of one order of magnitude. Especially reversal excursions, as expressed by magnetization directions differing largely from the expected dipole direction for a certain site, are associated with pronounced lows in the field intensity. So, in principle, determination of the sediment’s magnetization in terms of direction and intensity of time-calibrated curves can provide a detailed age model of (late) Quaternary sediments.
EN
Paleomagnetic and rock-magnetic study presented here concern the Upper Carboniferous (Namurian-Westphalian) sediments from the Intra-Sudetic Basin in the western Sudetes. The sampled rocks belong to the Wałbrzych (CW), Biały Kamień (CB) and Zacler (CZ) formations. Rock-magnetic investigations reveal presence of a small amount of magnetite and maghemite in pseudosingle-domain (PSD), single-domain (SD) and rarely multi-domain (MD) grains accompanied with goethite and hematite. Several groups of natural remanent magnetization (NRM) components were isolated from the demagnetization results; three of them, labeled T, A and A1, can be interpreted in terms of the geomagnetic field; the T component is a Mesozoic (or recent) overprint; the A component with the mean direction of D = 190°, I = -13° and the Virtual Geomagnetic Pole (VGP) Lat = 45°N and Long = 181°E is the post-tilting Autunian-Saxonian overprint; and A1 component with the mean direction of D = 196°, I = 24° and the VGP of Lat = -25°N and Long = 358°E is the pre-tilting one fitting the Westphalian segment of the APWP of Baltica. The origin of the remaining components, labeled B and C, is still an open question. Results of this study suggest that the investigated area has not undergone any important rotation since the Westphalian time.
EN
Research performed for Leszczyniec hornblende gneisses comprises paleomagnetic and rock magnetic study. Thermomagnetic and microscopic investigations indicate that magnetic properties of the gneisses are carried mainly by minerals formed or altered and/or magnetized due to deformational stages. The most important changes are related to the stage D1 that took place in the amphibolite facies conditions and ended at the Devonian-Carboniferous boundary. Low field magnetic susceptibility and its anisotropy are in major part related to paramagnetic hornblende. The directions of magnetic lineation before tectonic correction remain in agreement with directions of stretching lineation found in the Leszczyniec (LE) unit. Paleomagnetic study reveals presence of nine components of characteristic remanence. Five of them, labeled T, A, A1, A2 and CP may be interpreted in terms of the geomagetic field or geomagnetic field and tectonics. Component T (in situ) represents Mesozoic overprint, components A and A1 (both in situ) represent Early Permian and Middle Carboniferous overprints, respectively. Components A2 and CP represent geomagnetic field from the pre-tectonic times. In order to interpret them we assumed anticlockwise rotation of the LE unit around the vertical intraplate axis by 80 remaining in agreement with its sinistral shearing connected with the Dl deformational stage stated by Mazur (1995). This procedure shifted the tectonically corrected A2 pole position to the Devonian segment of the reference APW path for Baltica and the CP pole to its Ordovician segment. These results suggest that the LE unit was close to the Baltica perhaps even since the Ordovician and became rotated anticlockwise by about 80 at the final phase of the D1 stage (Upper Devonian-Lower Carboniferous). Despite the apparent logic of the presented results, there is always a possibility that the A2 and CP components of NRM are artefacts as are probably the remaining four isolated components CN, BW, BE1 and BE2.
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