BazTech - Yadda

1

Detrital zircon age data from the conglomerates in the Upper Silesian and Małopolska blocks, and their implications for the pre-Variscan tectonic evolution (S Poland)

Habryn Ryszard, Krzemińska Ewa, Krzemiński Leszek, Markowiak Marek, Zieliński Grzegorz

Geological Quarterly

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2020

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Vol. 64, No. 2

321--341

EN

Detrital zircon age of the conglomerates from the Upper Silesian (USB) and Małopolska (MB) (S Poland) have been investigated to compare their deposition age and possible provenience. The size and poor sorting of the lithoclasts reflect a short transportation, with deposition close to the sourceland. The Late Ediacaran conglomerate of the Potrójna IG 1 and Raciechowice 1 boreholes (USB) reveal a good match between the ages known from the local basement explored by boreholes. Detrital zircon clusters in a range of 579-585 Ma and 628-638 Ma and of 707 Ma are consistent with the distributions of Cadomian magmatism within the nearest orogenic belt or those identified elsewhere within the Brunovistulicum. In case of the conglomerate deposited in the Batowice 2 borehole (MB), the zircon clusters of 532, 551, 594 and 649 Ma, accompanied with a pre-Svecofennian group peaked at 2071 Ma, and the lack of Sveconorvegian population may document a tectono-sedimentary interaction between the Baltica's southern margin and the Gondwanan Cadomian and Late Cadomian basement during Early Paleozoic time. This conglomerate bed was deposited later, after the Early Ordovician, then docking of Małopolska Block - Baltica was probably completed.

2

Palaeozoic palaeogeography of the East European Craton (Poland) in the framework of global plate tectonics

Golonka Jan, Porębski Szczepan J., Barmuta Jan, Papiernik Jan, Bębenek Sławomir, Barmuta Maria, Botor Mariusz, Pietsch Kaja, Słomka Tadeusz

Annales Societatis Geologorum Poloniae

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2019

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Vol. 89, No. 4

381--403

EN

Global palaeogeographic maps were constructed for eight time intervals in the Palaeozoic. The maps contain information concerning plate tectonics and palaeoenvironment during the Cambrian, Ordovician, Silurian, Devonian and Carboniferous. The East European Craton belonged to the Palaeozoic Baltica Plate, which originated as a result of disintegration of the supercontinent Pannotia during the early Cambrian. Baltica included part of Poland and adjacent areas northeast of a line that extends between Scania and the Black Sea. This plate was located in the Southern Hemisphere and drifted northward during Early Palaeozoic time. The Early Ordovician was the time of maximum dispersion of continents during the Palaeozoic. Avalonia probably started to drift away from Gondwana and moved towards Baltica during Ordovician time. Between Gondwana, Baltica, Avalonia and Laurentia, a large longitudinal oceanic unit, known as the Rheic Ocean, was formed. Avalonia was probably sutured to Baltica by the end of the Ordovician or in the Early Silurian. This process was dominated by the strike-slip suturing of the two continents, rather than a full-scale continent-continent collision. Silurian was a time of Caledonian orogeny, closing of the Early Palaeozoic oceans, collision of Baltica with Avalonia and Laurentia and the assembly of the supercontinent Laurussia. The Variscan orogeny in Poland was caused by the collision of the Bohemian Massif plates and the Protocarpathian terrane with Laurussia. The Protocarpathian terrane acted as an indentor that caused thrust tectonics in the East European Platform, Holy Cross Mountains and the Lublin area.

3

Facies architecture of the Cambrian succession at the western margin of Baltica in the Podlasie region (E Poland)

Wendorff Marek

Annales Societatis Geologorum Poloniae

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2019

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Vol. 89, No. 4

453--469

EN

Sedimentary features of the Cambrian-age succession transected in seven borehole cores sited in the Podlasie region document vertical and lateral variations of shallow-marine sedimentary facies, deposited at the rifted western margin of the Baltica Palaeocontinent. The boreholes are distributed along two lines of cross-section (E–W and NE–SW) running roughly perpendicular to the margin of the palaeocontinent. The easternmost borehole represents a proximal setting located on a relatively stable, shallow basement in the east; the remaining boreholes document conditions of deposition in the subsiding shallow-marine basin, extending towards the SW. Fourteen sedimentary facies defined on the basis of their lithological and sedimentary features are interpreted in terms of the sedimentary environments they represent. Strata deposited upon the stable craton in the east document a stratigraphically condensed succession of proximal facies, 240 m thick, whereas a sequence three times thicker is positioned distally, 170 km to the west. Facies associations in the proximal section represent the lower to upper shoreface in the lower part of the section and evolve upwards to the intermediate shoreface. Facies complexes in the remaining, intermediate and distal areas form a symmetrical megasequence, composed of a positive (i.e., fining-upwards – FU) transgressive sequence, overlain by a negative (coarsening-upwards – CU) regressive sequence. The vertical arrangement of the sedimentary subenvironments during the transgression indicates a tidally influenced shoreline followed by oscillations between the swash zone, the upper, intermediate and lower shoreface, and the offshore. The symmetry of the megasequences and the rhythmic pattern of the component facies complexes indicate that the intensity of supply in the terrigenous material and the efficiency of its reworking and redistribution within the basin were similar during the transgression and the regression. The facies types and variations within the basal part of the succession reflect syndepositional movements of tectonic blocks parallel to the rifted basin margin. Differences in total thickness and facies associations between the two lines of cross-section approximately perpendicular to the basin margin indicate that sedimentation was also influenced by a synsedimentary hinge fault, extending in a WSW–ENE direction.

4

Facies architecture of the Cambrian deposits of the Baltica shelf in the Lublin Basin, SE Poland

Stadnik Renata, Bębenek Sławomir, Waśkowska Anna

Annales Societatis Geologorum Poloniae

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2019

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Vol. 89, No. 2

105--120

EN

In the Cambrian, the Lublin Basin was a shallow-water area, located on the western edge of the Baltica palaeocontinent. The Cambrian sedimentary sequence, forming the lower part of the sedimentary cover of the North European Platform, is lithologically diversified and reflects dynamic variation in depositional environment. This paper presents the distribution of palaeofacies and sedimentary environments in the early Lublin Basin, including changes in their lateral extent during its evolution in the Cambrian. In order to evaluate the facies architecture of the Lublin Basin, a sedimentological analysis was carried out. On the basis of the detailed logging of drill cores, lithofacies made up of conglomerates, sandstones, mudstones and heterolithic deposits were distinguished; 16 lower-rank sublithofacies were identified. Their specific assemblages are indicative of shelf-type lithofacies associations, i.e. (1) tidal flat with muddy, mixed and sandy tidal plain sublithofacies including subtidal channels; (2) barrier-lagoon; (3) shoreface with lower, middle and upper shoreface subassociations; and (4) offshore with upper and lower offshore subassociations, including sandy tidal ridges. During the early Cambrian, the lateral variability and environmental succession indicate a transgressive, long-term trend and the migration of a lagoonal environment across wide tidal plains and the shoreface up to an offshore environment. The Lublin Basin reached its greatest lateral extent and maximum depth in the upper lower Cambrian. Next, an opposite trend began and during the middle Cambrian a regression cycle is recorded in successive changes in sedimentary environments that reflect a progressive shallowing. Multiple changes in adjacent environments indicate repeated and cyclical, lower-rank ingressions.

5

A crustoid graptolite lithoimmured inside a Middle Ordovician nautiloid conch from northern Estonia

Vinn Olev, Wilson Mark A., Toom Ursula

Annales Societatis Geologorum Poloniae

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2019

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Vol. 89, No. 3

285--290

EN

A light grey nautiloid conch has a dark brown colony attached to its internal surface. This colonial fossil resembles hederellids and bryozoans, but is in fact a crustoid graptolite (Hormograptus? sp.). The colony has been lithoimmured inside this nautiloid conch by early cementation. Crustoid graptolites were a part of the encrusting communities in the Middle Ordovician of Baltica, but their abundance among encrusters of biogenic substrates reached a peak in the middle Sandbian. The cryptic mode of life appeared very early in the evolution of the crus- toids. The discovery of this crustoid graptolite in a nautiloid conch indicates that the Baltic Middle Ordovician cryptic communities were taxonomically more diverse than was known previously. The nautiloid conch studied is sparsely encrusted with an encrustation density that is similar to those of other Middle Ordovician cryptic surfaces described from Estonia.

6

Large cruzianid trace fossils in the Ordovician of the peri-Baltic area : the case of the Bukówka Formation (Holy Cross Mountains, Poland)

Stachacz M., Łaska W., Uchman A.

Geological Quarterly

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2018

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Vol. 62, No. 2

400--414

EN

The Middle Ordovician Bukówka Formation, composed of fine-grained quartz sandstones with siltstone intercalations, belongs to the Kielce Region of the Holy Cross Mountains (peri-Baltic palaeogeographic position). It contains trace fossils of low diversity and poor preservation. Particularly noteworthy are the large Cruziana and Rusophycus, that are typical of peri-Gondwanan areas. They consist of casts of bilobate furrows showing diverse preservation. Other trace fossils include mostly horizontal pascichnia, cubichnia, and fodinichnia, but also vertical domichnia. The trace fossil assemblage is typical of the archetypal Cruziana and partly of the Skolithos ichnofacies. Some beds contain abundant orthid brachiopods. The trace fossils and sedimentary structures (horizontal, low-angle and wave ripple cross-laminations, hummocky cross-stratification) suggest deposition on the middle and lower shoreface with storm influence. The poor preservation and low diversity of the trace fossils are related to the homogeneous lithology, low accumulation rate, shallow burial of organic matter and strong bioturbation. Therefore, animals burrowed strongly but mostly in shallow tiers. Thus, the preservation potential of their traces was much lower than in many peri-Gondwanan sections but still higher than in Baltica sedimentary rocks. This explains the provincial differences in ichnofauna during the Ordovician, which at least partly were influenced by the preservation potential.

7

Cryptic encrusting fauna inside invertebrate fossils from the Ordovician of Estonia

Vinn O., Ernst A., Toom U., Isakar M.

Annales Societatis Geologorum Poloniae

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2018

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Vol. 88, No. 3

285--290

EN

This is the first report of encrusted cryptic surfaces in the Ordovician of Estonia. Only bryozoans and cornulitids occurred in nautiloids and trilobites. Bryozoans were the dominant encrusters, in terms of both the number of specimens and the encrustation area. Stalked echinoderms are common on the hardgrounds in the Middle and Upper Ordovician of Baltica, but the restricted space in nautiloid living chambers and trilobites probably prevented colonization by stalked echinoderms. Cryptic surfaces in nautiloids and trilobites usually are somewhat more encrusted than the open surfaces of hardgrounds in the Ordovician of Estonia. Encrusters presumably favoured cryptic surfaces, as these were less accessible for predators and grazers. Low encrustation densities, compared to North American hard substrates, seem to be characteristic for the Ordovician Baltic Basin.

8

Zachodnie przedpole kratonu wschodnioeuropejskiego : paleozoiczne terrany czy marginalna część kontynentu Bałtyki?

Mizerski W., Olczak-Dusseldorp I.

Przegląd Geologiczny

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2017

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Vol. 65, nr 12

1521--1528

EN

Provenance of the tectonic blocks located in the recent, western foreland of the East European Craton in Poland is subject to debate. These blocks are regarded either as Avalonian blocks adjacent to the East European Craton along the T-Tzone or accretional wedge (or its fragments) formed during the collision of Baltica and Avalonia. This implies that the western edge of the Baltica Continent was active, with a subduction zone developed along which Avalonian blocks and Baltica should be smashing together Baltica. However, no objective geological facts indicate the occurrence of a subduction zone along the present-day SW edge of the East European Craton. On the contrary, there are many evidences indicating the sedimentation taking place in a continental passive margin during the Palaeozoic and there is no proof that the older Palaeozoic rocks are thrust over the Baltic margin. Consequently, tectonic deformation in Palaeozoic rocks, recorded in the present-dayforeland of the East European Craton, are related to the mobility of the craton margin and should be regarded as platform-type deformation.

9

Bentonit środkowokambryjski z otworu Borcz-1 z basenu bałtyckiego

Kowalska S., Zagórska U., Mikołajewski Z.

Nafta-Gaz

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2016

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R. 72, nr 12

1043--1048

PL

Nie odnotowano dotąd obecności śladów aktywności wulkanicznej w utworach kambryjskich występujących na obszarze polskiej części skłonu platformy wschodnioeuropejskiej. Dzięki nowym wierceniom prowadzonym przez PGNiG SA podczas poszukiwania gazu w pokładach łupków w otworze Borcz-1 udało się znaleźć cienką 3-centymetrową wkładkę bentonitową w obrębie utworów kambru środkowego. W prezentowanym artykule przedstawione zostaną pierwsze wyniki badań wykonanych w celu przeprowadzenia charakterystyki mineralogicznej powyższej skały. Analiza pierwiastków śladowych pozwoliła na określenie przybliżonego składu pierwotnego materiału wulkanicznego, wskazując na obojętny, trachyandezytowy charakter magmy macierzystej. Materiał wulkaniczny pochodził najprawdopodobniej z rejonu aktywnej krawędzi kontynentu.

EN

Traces of volcanic activity in the Cambrian rocks occurring within the Polish part of the East European Platform slope has not been recorded to date. Thanks to new shale gas exploration conducted by PGNiG SA a thin, 3 cm thick, bentonite layer was found within the Middle Cambrian strata in the Borcz-1 borehole. This article presents the first results of studies carried out, in order to perform mineralogical characteristics of the above rock. Analysis of trace elements composition, allowed us to determine the approximate initial composition of original volcanic material pointing to an intermediate, trachyandesitic parent magma. Volcanic material probably came from an active continental margin.

10

Epi- and endobionts on the late Silurian (early Pridoli) stromatoporoids from Saaremaa Island, Estonia

Vinn O., Wilson M. A.

Annales Societatis Geologorum Poloniae

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2012

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Vol. 82, No. 3

195--200

EN

A diverse sclerobiont community is described from the Kaugatuma Formation (lower Pridoli) of Saare- maa, Estonia. The stromatoporoid substrates studied here vary from low-domical to high-domical shapes. The community is numerically dominated by microconchids, which may have been characteristic of the sclerobiont fauna in the Pridoli of Baltica. Palaeoconchus aff. tenuis, Anticalyptraea calyptrata, Aulopora sp., sheet-like bryozoans, branching bryozoans, erect bryozoan holdfasts, rugosans, favositids, discoidal crinoid holdfasts, star- like crinoid holdfasts and sheet-like stromatoporoids encrust the domical stromatoporoids. Endobionts are repre- sented by embedded, symbiotic rugosans, Aulopora sp., and two rare borings Trypanites.

11

More evidence on Neoproterozoic terranes in Southern Poland and southeastern Romania

Żelaźniewicz A., Buła Z., Fanning M., Seghedi A., Żaba J.

Geological Quarterly

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2009

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Vol. 53, No 1

93-124

EN

New geological, geochemical and U-Pb SHRIMP zircon age data brought more information about basement units in subsurface of Southern Poland and SE Romania, which allows to revise and refine some earlier models in the framework of the break-up of the Rodinia/Pannotia supercontinent. In the Brno Block, Moravia, and in the Upper Silesia Block, three different terranes formed the composite Brunovistulia Terrane. The Thaya Terrane (low eNd(T)) of Gondwana (Amazonia) descent collided obliquely at 640–620 Ma with the Slavkov Terrane (moderate eNd(T)) composed of amphibolite facies metasediments and arc-related, mostly unfoliated granitoids which intruded at 580–560 Ma. At that time, back-arc rifting separated the couple Thaya–Slavkov (inherited zircons: 1.01–1.2, 1.4–1.5, 1.65–1.8 Ga) that drifted away from Gondwana until collision around 560–550 Ma with the Rzeszotary Terrane, the Palaeoproterozoic (2.7–2.0 Ga) crustal sliver derived from Amazonia or West Africa. At least these three units composed Brunovistulia, which occurred at low latitudes in proximity to Baltica as shown by palaeomagnetic and palaeobiogeographic data. Then Brunovistulia was accreted to the thinned passive margin of Baltica around its Małopolska promontory/proximal terrane. A complex foreland flysch basin developed in front of the Slavkov–Rzeszotary suture and across the Rzeszotary–Baltica/Małopolska border. The further from the suture the less amount of the 640–550 Ma detrital zircons extracted from the Thaya–Slavkov hinterland and the smaller eNd(T) values. In West Małopolska, the flysch contains mainly Neoproterozoic zircons (720–550 Ma), whereas in East Małopolska 1.8–2.1 Ga and 2.5 Ga zircons dominate, which resembles nearby Baltica. The basin infill was multiphase folded and sheared; in Up per Silesia prior to deposition of the pre-Holmia Cambrian over step. In Małopolska, the folded flysch series formed a large-scale antiformal stack with thermal anticline in its core marked by low-grade metamorphic overprint. In Central Dobrogea, Moesia, Ediacaran flysch also contains mainly 700–575 Ma detrital zircons which link the source area, likely in South Dobrogea with ca. 560 Ma granitoids, rather close with Gondwana. However, fauna in Lower Cambrian overstep strata shows Baltican affinity. Such features resemble Upper Silesia, thus Brunovistulia might have extended beneath the Carpathians down to Moesia. The other part of South Dobrogea with Palaeoproterozoic ironstones resembles Ukrainian banded iron formation. If true, the Baltican sliver would be incorporated in Moesia. Such a possibility concurs with the provenance data from Ediacaran flysch of Central Dobrogea, which points to uplifted continental block as a source of derital material. Our study supports an earlier proposition that at the end of the Neoproterozoic a group of small terranes that included Brunovistulia, Moesia and Małopolska formed the Teisseyre-Tornquist Terrane As semblage (TTA). In our model, a characterisistic feature of the TTA was a mixture of crustal elements that were derived from both Gondwana and Baltica, which gave rise to mutual collisions of the elements prior to and concurrent with the docking to Baltica in latest Ediacaran times. The presence of extensive younger covers and complex Phanerozoic evolution of individual members of the TTA impede the recognition of their Neoproterozoic history.

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Palaeomagnetic age of remagnetizations in Silurian dolomites, Rástla quarry (Central Estonia)

Plado J., Preeden U., Puura V., Pesonen L. J., Kirsimäe K., Pani T., Elbra T.

Geological Quarterly

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2008

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Vol. 52, No 3

213-213

EN

Alternating field and thermal demagnetization of dolomite samples from the Silurian (Llandovery) horizontally-bedded sequence of central Estonia reveal two secondary magnetization components (A and B) both of chemical origin. A low-coercivity (demagnetized at -50 mT) component A (D = 60.7°, I = 7.7°, alfa95 = 16.6°) with high dispersion (k = 14.2), yields a palaeopole at 18.2°N and 139.5°E that points towards the Late Devonian — Mississipian segment of the Baltica APWP (Apparent Polar WanderPath). A high-coercivity component B (D = 13.5°, I = 60.7°, k = 67.0, alfa 95 = 4.7°) carries both normal and reversed polarities. Comparing the palaeopole (71.1°N and 173.3°E) with the European APWP reveals a Cretaceous age. These two remagnetizations are linked to mineral assemblages of magnetite and maghemite (A), and hematite (B) determined from mineralogical (X-ray, SEM and optical microscopy) and rock magnetic (acquisition and thermal demagnetization of a 3-component IRM; Lowrie-test) studies. The results suggest that the first (A) Palaeozoic remagnetization was caused by low-temperature hydrothermal circulation due to the influence of the Caledonian (more likely) or Hercynian Orogeny after the diagenetic dolomitization of carbon ates. Hematite, carrying the component B, and goethite, are the latest ferromagnetic minerals that have precipitated into the existing pore space (hematite) and walls of microscopic fractures (goethite) that opened to allow ac cess for oxygen-rich fluids during the Late Mesozoic.

13

The Middle Cambrian paradoxidid trilobite Hydrocephalus from Jamtland, central Sweden

Rushton A.

Acta Geologica Polonica

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2007

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Vol. 57, no. 4

391-401

EN

A new paradoxidid species, Hydrocephalus vikensis, is described from the lower Middle Cambrian praecurrens Zone in Jamtland, central Sweden. It is contrasted with typical Hydrocephalus species and shows features that recall Paradoxides. The genus Hydrocephalus BARRANDE is discussed; the validity of the related genus Rejkocephalus KORDULE is considered to be doubtful. The associated fauna is listed and an agnostoid that differs slightly from Condylopyge regia (SJOGREN) is illustrated.

14

Budowa geologiczna głębokiego podłoża platformy paleozoicznej południowo-zachodniej Polski w świetle wyników eksperymentu sejsmicznego Polonaise’97

Mazur S., Jarosiński M.

Prace Państwowego Instytutu Geologicznego

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2006

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T. 188

203--222

PL

Profile sejsmiczne eksperymentu POLONAISE’97 dokumentują budowę wgłębną strefy szwu transeuropejskiego (TESZ), który stanowi szeroką strefę akrecji terranów na pograniczu proterozoicznej litosfery kratonu wschodnioeuropejskiego oraz młodszej, paleozoicznej litosfery zachodniej Europy. Uzyskane rezultaty sondowań sejsmicznych, w połączeniu z danymi pól potencjalnych i modelami termicznymi, pozwalają na wydzielenie 5 typów litosfery: (1) typ LEEC — litosfera kratonu wschodnioeuropejskiego, (2) typ LTTZ — bloki litosfery przylegające bezpośrednio do kratonu wschodnioeuropejskiego i sięgające po południowo-zachodnią granicę wału śródpolskiego, (3) typ LTES — skorupa szwu transeuropejskiego pomiędzy LTTZ a strefą tektoniczną Dolska, (4) typ LPP — fragment litosfery pomiędzy strefą Dolska a uskokiem środkowej Odry, (5) typ LVP występujący na południe od strefy uskokowej środkowej Odry. Dwa pierwsze typy litosfery (LEEC i LTTZ) są genetycznie związane z Baltiką. Litosfera typu LTES i LPP stanowi osobny blok podłoża, który wywodzi się z Awalonii lub ze spokrewnionego z nią terranu przyłączonego do brzegu Baltiki we wczesnym paleozoiku. Jej struktura sejsmiczna jest prawdopodobnie wypadkową szeregu hipotetycznych czynników, takich jak m.in. wczesnopaleozoiczne podklejanie dolnej skorupy przez magmy wytapiane z subdukowanej płyty oceanu Tornquista, kolizja kaledońska czy wieloetapowe przemieszczenia przesuwcze. Litosfera LPP została również przebudowana w efekcie głęboko zakorzenionej tektoniki waryscyjskiej. Litosfera typu LVP należy do orogenu waryscyjskiego i stanowi fragment Armoryki. Granice pomiędzy blokami litosfery najwyższej rangi, takimi jak Baltika, Awalonia i Armoryka, zaznaczają się subtelnie w obrazie sejsmicznym. Większe kontrasty w strukturze sejsmicznej mogą występować w obrębie jednorodnych genetycznie fragmentów litosfery, rozczłonkowanych przez główne strefy dyslokacyjne.

EN

Seismic profiles of the POLONAISE'97 experiment provide evidence for the deep basement structure of the TESZ area representing a broad and complex zone of terrane accretion which separates the old Proterozoic lithosphere of the East European Craton (EEC) from the younger Palaeozoic lithosphere of western Europe. The obtained results combined with potential field data allows the differentiation of 5 varieties of lithosphere: (1) LEEC variety -a lithosphere of the East European Craton, (2) L TTZ variety -lithospheric blocks adjacent to the EEC and extending to the south-western margin of the Mid-Polish Swell belonging to the Teisseyre-Tornquist Zone (TTZ), (3) LTES variety - a lithosphere of the Trans European Suture Zone (TESZ) between the L TTZ and the Dolsk Fault Zone, (4) LPP variety- a segment of the lithosphere be-tween the Dolsk Fault Zone and the Middle Odra Fault Zone, (5) L VP variety occurring to the south-west of the Middle Odra Fault Zone belonging to the typical Variscan platform. The two types LEEC and LTTZ are genetically linked to Baltica, while LTES and LPP represent a lithosphere of Avalonia. A lithosphere of the Palaeozoic Platform (LTES), embraced between the Variscan orogen and the EEC, represents a separate basement błock derived from Avalonia or an Avalonia-related terrane accreted to the Baltica margin during the Early Palaeozoic. The three-layer seismic structure of a crust in that area is probably produced by a number of superimposed effects like under platting by magmas melted off from a subducted plate of the Tornquist ocean. The results of the POLONAISE'97 experiment verify the role of the Dolsk Fault Zone as the northeastern boundary of the area affected by a thick-skinned Variscan tectonics. The Variscan-related modification of a seismic structure has its effect not only on a lithosphere of the Bohemian Massif, usually correlated with the Arrnorica terrane assemblage, but also on a fragment of the Palaeozoic platform of southwestern Poland located between the Dolsk Fault Zone and Middle Odra Fault Zone.

15

New Late Vendian palaeogeography of Baltica and the TESZ

Nawrocki J., Boguckyj A., Katinas V.

Geological Quarterly

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2004

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Vol. 48, No 4

309--316

EN

New palaeomagnetic poles obtained from the Vendian tuffs and basalts of western Ukraine indicate the necessity of a substantial revision of the Late Vendian-Early Cambrian palaeogeography of the Baltic plate. The palaeopole calculated for the most stable component isolated from the Vendian tuffs and basalts is far away from the Vendian-Cambrian apparent polar wander path (APWP), constructed on the basis of Scandinavian poles but is very close to the pole recently isolated from the Vendian sediments of the White Sea Region. Depending on the polarity of the newly-determined Late Vendian pole, two palaeogeographic models of the Baltic plate in the Late Vendian-Early Cambrian are possible. In our preferred model the Baltic plate moved at that time from the moderate southern latitudes to the equator rotating anticlockwise of ca. 120 degrees Celsius. This reconstruction explains the geological structures of the marginal zones of Baltica better than the previously proposed stationary model of the Late Vendian-Cambrian Baltica. According to the new late Vendian palaeogeographic scenario, the European, passive margin of Baltica was separated from an active, Avalonian margin of Gondwana. The Late Neoproterozoic tectonic structures of the Brunovistulian Terrane and the Małopolska Block were developed near the present day southwestern corner of Baltica that was tectonically active at that time. Alternative reconstruction shows the Baltic platemoving from the moderate northern latitudes in the Vendian, crossing palaeoequator in the latest Vendian, and reaching moderate southern palaeolatitudes in the Late Cambrian. This model, however, would have required exceptionally high plate velocity (ca. 33 cm/year).

16

Chitinozoans and acritarchs from the Ordovician of the Skibno 1 borehole, Pomerania, Poland : implications for stratigraphy and palaeography

Wrona R., Bednarczyk W., Stempień-Sałek M.

Acta Geologica Polonica

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2001

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Vol. 51, nr 4

317-331

EN

Biostratographical results of this palynological study agree with those of previous research on graptolites from the Ordovician of the Skibno 1 borehole in the Koszalin - Chojnice Structural Zone, Polish portion of the Pomerania Terrane. They indicate that the investigated core interval can be attributed to the uppermost Llanvirn (Landeilo) - lower Caradoc, and correspond to the teretiusculus and gracilis through the multidens graptolite biozones. Recovered chitinozoan species, including Belonechitina robusta, Conochitina chydaea, C. dolosa, Lagenochitina aff. capax, Spinachitina bulmani, and the index species Laufeldochitina stentor are restricted to the upper Llanvirn - lower Caradoc, the latter species delimits the stentor chitinozoan biozone (upper Uhaku and Kukruse stages). The following identified acritarchs are regarded as biosratigraphically significant: Goniosphaeridium splendens, Ordovicidum elegantulum, O. heteromorphicum, O. nanofurcatum, O. nudum, and are characteristic for the Caradoc. The presence of conodont Scabbardella altipes and ichnofossil Alcyonidiopsis pharmaceus, both characteristic of high palaeolatitudes, as well as lithological similarities between the investigated strata and their equivalents from Rugen indicate that Pomerania could have been situated at relatively high latitudes during the upper Llanvirn to lower Caradoc. These observations together with palynological results support a hypothesis that Pomerania was a terrane derived from Avalonia and accreted to the margin of the East European Craton.