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| Geological Quarterly (2000) - Vol. 44-03 |
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| By GQ |
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Ryszard DADLEZ
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Pomeranian Caledonides (NW Poland), fifty years of controversies: a review and a new concept
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............221
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The results of a half-century investigations of the Pomerania-Rügen Caledonides are reviewed. Fifty years ago there were two rival hypotheses based exclusively on analyses of gravity and magnetic data. One of them assumed the presence of the so-called Circum-Fennosarmatian Caledonides, the second one claimed that the Precambrian craton of the eastern Europe extends far to the west reaching northern Germany and Pomerania. As time passed, more new facts from boreholes and seismic refraction and reflection studies accumulated. New hypotheses appeared, namely the concepts of an aulacogen and a major strike-slip fault, now merely of a historical importance. In spite of the new data the principal dilemma remains the same until present. Some investigators believe that the East European Craton (Baltica) extends far to the south-west reaching the Elbe-Odra Line, others assume the presence of the Caledonian deformations in Rügen and Pomerania which are regarded - according to modern concepts - as a manifestation of terrane tectonics. The latter group of hypotheses is supplemented by the author with the model of proximal terranes detached from the craton margin farther to the south-east and then re-accreted. The hypothesis is based on an analysis of differences in crustal structure in northern Germany and western Poland, and on the concept of a counter-clockwise rotation of Baltica during the Ordovician, proved by palaeomagnetic data.
Ryszard Dadlez, Polish Geological Institute, Rakowiecka 4, PL-00-975 Warszawa, Poland (received: August 26, 1999; accepted: October 15, 1999).
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Magdalena SIKORSKA
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Provenance petrological study of the Upper Vendian and Cambrian clastic material; foreland of the Pomeranian Caledonides (northern Poland)
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............237
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The provenance of clastic material in the oldest part of the sedimentary cover of the East European Craton, in northern Poland, is analysed. Analysis of the Żarnowiec Formation sandstones (Upper Vendian-lowest Cambrian) confirm earlier views of a local origin. The crystalline basement in the Kościerzyna IG 1 region mainly yielded enderbitic detritus while that in the Gdańsk IG 1 region provided migmatitic detritus. Triangle diagrams of the overlying, mature, sandy marine Cambrian show unequivocally that the detritus was transported from the craton interior. Analysis of mono- and polycrystalline quartz and cathodoluminescence (CL) analysis indicates erosion of metamorphic, magmatic and sedimentary rocks, and this is confirmed by CL observations of zircons. These results are consistent with the view that the Upper Vendian and Cambrian strata on the Pomeranian Caledonides foreland were formed on the passive margin of Baltica.
Magdalena Sikorska, Polish Geological Institute, Rakowiecka 4, PL-00-975 Warszawa, Poland (received: September 30, 1999; accepted: October 15, 1999).
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Krzysztof JAWOROWSKI
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Facies variability in the Cambrian deposits from the Kościerzyna and Gdańsk sections (Pomeranian Caledonides foreland, northern Poland): a comparative study
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............249
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The origin of Cambrian clastics occurring in the marginal part of the East European Craton, in the foreland of the Pomeranian Caledonides is discussed. They were deposited in an epicontinental sea influenced by tides and storms. The first Lower Palaeozoic transgressive-regressive (T-R) cycle spans the Lower and most of the Middle Cambrian. The maximum transgression in the craton-margin part (Kościerzyna section) is marked by submarine erosion and a very low deposition rate around the Lower/Middle Cambrian boundary. The condensed deposit is a limestone - shell hash packstone with phosphatized mudstone clasts. In the inner part of the craton (Gdańsk section), the condensed deposit is represented by mudstones and heterolithic deposits with iron ooids. Transgressive phase deposits of the first T-R cycle from the Kościerzyna section are 323.5 m thick, while regressive phase deposits - 273.7 m thick. In the Gdańsk section the thicknesses are of 113.0 and 218.8 m, respectively. Deposits of the first T-R cycle of northern Poland and the Polish part of the Baltic Sea are overlain by those of the second T-R cycle, which, when complete, comprise the uppermost Middle Cambrian, Upper Cambrian and Lower Tremadoc. In both the sections discussed, deposits of the second T-R cycle were almost completely removed by pre-Arenig erosion. Facies analysis of deposits of the first T-R cycle from the Kościerzyna and Gdańsk sections shows that the source areas of terrigenous material, during both transgressive and regressive phases of this cycle, were elevated zones of the East European Craton.
Krzysztof Jaworowski, Polish Geological Institute, Rakowiecka 4, PL-00-975 Warszawa, Poland (received: September 30, 1999; accepted: February 10, 2000).
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Zbigniew SZCZEPANIK
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The Cambrian of the western part of the Pomeranian Caledonides foreland, Peribaltic Syneclise: microfloral evidence
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............261
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This paper describes the microfloral succession in Cambrian deposits in the Kościerzyna IG 1 and Gdańsk IG 1 boreholes drilled in the western part of the Peribaltic Syneclise, immediately adjoining the T-T Zone in the Pomeranian Caledonides foreland. Both these boreholes have yielded abundant acritarch assemblages that allow the partial zonation of the Lower and Middle Cambrian deposits. The Cambrian deposits of the Kościerzyna IG 1 borehole comprise the following microfloral zones: Asteridium tornatum-Comasphaeridium velvetum, Skiagia ornata-Fimbriaglomerella membranacea and Heliosphaeridium dissimilare-Skiagia ciliosa. The Volkovia dentifera-Liepaina plana Zone may also be present. The Acadoparadoxides pinus Zone (upper part of the A. oelandicus Superzone), well documented by trilobites, might correlate with the Cristallinium cambriense-Eliasum Superzone. This conflicts with the findings of Jankauskas and Lendzion (1992), who restricted the range of the commonly occurring C. cambriense (Slavikova) only to the Paradoxides paradoxissimus Superzone and younger deposits. The Lower Cambrian Skiagia-Fimbriaglomerella and (or) Heliosphaeridium-Skiagia Zones have been documented in the Gdańsk IG 1 borehole. As in the Kościerzyna IG 1 borehole, abundant Middle Cambrian acritarchs of the C. cambriense-Eliasum Superzone define the presence of rocks not older than equivalents of the A. pinus Zone. Palynomorphs from the Kościerzyna IG 1 borehole correspond to stage 6 of the AMOCO thermal alteration scale, i.e. to palaeotemperatures considerably exceeding 100°C. The maximum palaeotemperature of the Cambrian rocks at Gdańsk has not exceeded 100°C.
Zbigniew Szczepanik, Holy Cross Mts. Branch, Polish Geological Institute, Zgoda 21, PL-25-953 Kielce, Poland (received: September 30, 1999; accepted: June 2, 2000).
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Zbigniew SZCZEPANIK
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The Ordovician acritarchs of the Pomeranian Caledonides and their foreland - similarities and differences
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............275
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Ordovician acritarch assemblages of the West Pomeranian Caledonides and their platformal foreland in the Peribaltic Syneclise immediately adjoining the T-T Zone were investigated. Material come from the Ordovician section of the Kościerzyna IG 1, Lębork IG 1 and Gdańsk IG 1 boreholes drilled in the marginal part of the East European Craton, though acritarchs were found only in two samples from the Gdańsk IG 1 borehole. In general, microflora was abundant and the investigations supported current ideas on the stratigraphical level of these rocks. The acritarch assemblages from the Gdańsk IG 1 borehole, found at a depth of 3214.8 m, contain species of Baltisphaeridium, characteristic of the Llanvirn and described by Górka from the eastern part of the Peribaltic Syneclise and the Podlasie Depression. The abundant microflora from West Pomerania contains index taxa of the uppermost Llanvirn (Llandeilo) and Caradoc. Numerous palynomorph associations from the Ordovician rocks of the Koszalin-Chojnice Zone can be divided into three local microfloral zones, using quantitative data, and these may be useful for local stratigraphical correlations. Acritarch assemblages on either side of the T-T Zone show many similarities and suggest that, in the late Llanvirn and Caradoc, there was little palaeogeographic separation between the sedimentary basins of Baltica and West Pomerania; at least, their palaeolatitudinal positions were similar. The thermal maturity of Ordovician organic matter (low and moderate) is also similar in both these areas. The highest heat flow values seem to be characteristic of the western part of the Peribaltic Syneclise, adjoining the T-T Zone. The degree of their thermal alterations in the West Pomeranian Caledonides is surprisingly low when the strong tectonic deformation and considerable depth of the Ordovician rocks are taken into account. The high morphological diversity of the acritarch assemblages, the presence of Baltisphaeridium and Ordovicidium, and especially of abundant Veryhachium, suggest that microflora from the Koszalin-Chojnice Zone represents an open-marine depositional palaeoenvironment, distant from the coast.
Zbigniew Szczepanik, Holy Cross Mts. Branch, Polish Geological Institute, Zgoda 21, PL-25-953 Kielce, Poland (received: September 30, 1999; accepted: June 2, 2000).
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Krzysztof JAWOROWSKI
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Facies analysis of the Silurian shale-siltstone succession in Pomerania (northern Poland)
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............297
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The Silurian deposits of Pomerania occur in the foreland of the Pomeranian Caledonides which are the SE continuation of the Danish-North-German Caledonides. The Silurian sequence in Pomerania is represented largely by graptolitic clay- and mud-shales deposited in a hemipelagic environment. From the Wenlock through Late Ludlow, slow deposition of hemipelagic clays and muds was repeatedly interrupted by silty debris flows and turbidity currents. Many of the siltstone interbeds were reworked by bottom currents. Clastic material was sourced from the Caledonian accretionary prism stretching along the collision zone of Baltica and East Avalonia. The Silurian shale-siltstone succession in Pomerania represents a Caledonian exoflysch i.e. syn-collision clastics accumulated in a foredeep developed on the East European Craton. The diachronous appearance of siltstone interbeds in the graptolitic shales indicate that collision between Baltica and East Avalonia was associated with sinistral strike-slip movement along the edge of the East European Craton.
Krzysztof Jaworowski, Polish Geological Institute, Rakowiecka 4, PL-00-975 Warszawa, Poland (received: September 30, 1999; accepted: February 10, 2000)
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Monika JACHOWCZ
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Acritarch assemblages from the Silurian Pomeranian Caledonides and their foreland
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............317
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Comprehensive palynological studies of the Silurian rocks of the Pomeranian Caledonides are described, the first since Eisenack's (1972) work. 250 clastic rock samples were analysed, all from deep boreholes. Three of these boreholes (Lębork IG 1, Gdańsk IG 1 and Kościerzyna IG 1) are located NE of the Teisseyre-Tornquist Zone (TTZ) and contain horizontal successions of the western, marginal part of the East European Craton. Other boreholes studied (Bydgoszcz IG 1, Klosnowo IG 1 and Stobno 1) penetrated folded Lower Palaeozoic sediments, and lie SE of the TTZ. The investigations included a complete Silurian profile from the Llandovery to the Poidoli, which is documented in detail by graptolites. Associations of microflora (Acritarcha, Prasinophyceae, Sporites) and microfauna (Chitinozoa, Scolecodonta) varied in quality and quantity. There was considerable variability in the preservation and thermal maturity of the organic-walled microfossils. Detailed investigations of the acritarchs are described. 7 characteristic acritarch assemblages have been distinguished, and these are correlated with the graptolite biozones. Llandovery rocks contain assemblages with Domasia, Ammonidium and Tylotopalla genera. Wenlock deposits include Tylotopalla, Leptobrachion and Cymbosphaeridium. The Upper Ludlow deposits contain well preserved assemblages with Visbysphaera, Veryhachium, Onondagella and Leoniella, accompanied by Neoveryhachium carminae, Geron gracilis, and some Deflandrastrum and Visbysphaera species generally considered characteristic of Gondwana. Throughout the Silurian profile, individual specimens of typical Ordovician genera such as Acanthodiacrodium, Frankea, Striatotheca and Coryphidium occur. The acritarch assemblages overall show mixed characters, typical of both Baltica and Gondwana.
Monika Jachowicz, Upper Silesian Branch, Polish Geological Institute, Królowej Jadwigi 1, PL-41-200 Sosnowiec, Poland (received: March 24, 2000; accepted: April 17, 2000).
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Anna ŚWIERCZEWSKA, Antoni K. TOKARSKI and Vratislav HURAI
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Joints and mineral veins during structural evolution: case study from the Outer Carpathians (Poland)
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............333
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This paper focuses on mineral veins hosted in small-scale fractures within the Tertiary sandstones of the Magura nappe (Outer Carpathians). Joints, faults and tension gashes record three successive stages of the nappe structural evolution: (1) synsedimentary folding and thrusting, (2) regional rotation and (3) late-orogenic collapse. The flow of mineral-bearing fluids was channelized by small-scale fractures resulting in calcite and quartz-calcite veins. Folding: columnar calcite formed the most common filling of early joints and the joints-related tension gashes and strike-slip faults. The mineralisation was restricted to sandstones containing primary carbonates. Rotation: precipitation of columnar and fibrous calcite was largely restricted to joints reactivated as strike-slip faults. Collapse: the collapse-related mineralisation is the most abundant. Wide-spread fluid flow was channelized by normal faults resulting in fibrous calcite and quartz-calcite along these faults whereas several blocky and drusy calcite generation and single high temperature quartz-calcite assemblage precipitated in numerous adjoining joints.
Anna Świerczewska and Antoni K. Tokarski, Institute of Geological Sciences, Polish Academy of Sciences, Senacka 1, PL-31-002 Kraków, Poland; Vratislav Hurai, Geological Survey of Slovakia, Mlynska dolina 1, 817-04 Bratislava, Slovakia (received: December 18, 1999; accepted: January 14, 2000).
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Jerzy NAWROCKI, Józef LIS, Jacek GRABOWSKI and Anna PASIECZNA
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The magnetic susceptibility of soils and alluvial sediments from Gdansk region (northern Poland)
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............341
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Volume magnetic susceptibility of soils and alluvial sediments from the eastern Pomeranian region near Gdańsk was investigated. Full set of geochemical analyses had been previously performed for all the samples studied. The results are presented in the form of the susceptibility maps of the topsoil horizon, the subsoil at the depth between 40 and 60 cm and the alluvial sediments. Additionally the differential susceptibility map between topsoil horizon and the subsoil at the depth 40-60 cm has been also constructed. A close correlation is observed between positive anomalies of differential susceptibility and urban areas. This is interpreted as surface anthropogenic pollution. Magnetic susceptibility values higher than 1200 x 10-6 SI units, observed in topsoil horizon, might reflect high contents of such elements as Ba, Co, Mg, Mn and Ni.
Jerzy Nawrocki, Józef Lis, Jacek Grabowski and Anna Pasieczna, Polish Geological Institute, Rakowiecka 4, PL-00-975, Warszawa, Poland (received: January 17, 2000; accepted: February 18, 2000).
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