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Anomalous Upper Devonian mercury enrichments : comparison of Inductively Coupled Plasma – Mass Spectrometry (ICP-MS) and Atomic Absorption Spectrometry (AAS) analytical data

Racki G., Rakociński M., Marynowski L.

Geological Quarterly

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2018

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Vol. 62, No. 3

487--495

EN

Mercury geochemistry is emerging recently as a hot topic in chemostratigraphical and facies research, owing to the diagnostic character of Hg enrichments as a proxy of volcanic activity (crucial in the context of assumed causal links between volcanic cataclysms and mass extinctions). Thus, as a prerequisite to such far-reaching interpretations, reliable analytical determinations of Hg concentrations are necessary. In conventionally performed analyses in sedimentary geochemistry, Inductively Coupled Plasma – Mass Spectrometry (ICP-MS) is usually applied, as an analytical standard for trace elements, including Hg. However, with a detection limit (DL) of 10 ppb, such measured values have been questioned as a conclusive geochemical indicator of Hg anomalies, and, instead, far more accurate techniques, such as Atomic Absorption Spectrometry (AAS; DL = 0.2 ppb), are requested. As a preliminary test of this view, we present comparative analysis of 91 samples from three sections encompassing the key Frasnian-Famennian and Famennian-Tournaisian boundary intervals in Morocco (Lahmida), Germany (Kahlleite) and Uzbekistan (Novchomok), for which Hg concentrations were determined by both methods in the same samples. Despite some differences, especially at low Hg concentrations, both analytical methods reveal the same 12 extraordinarily enriched samples in excess of 1 ppm (with one exception, the determination error is <20%), as well as similar overall chemostratigraphic patterns characterized by a few prominent Hg spikes, with a top value of 5.8 ppm. The Hg concentrations determined by ICP-MS and AAS are significantly correlated, as high as r = 0.98 (Novchomok), even if the first method reveals a general tendency toward slightly heightened values (by ~15 to 30% for medians). Therefore, ICP-MS results can conclusively be used in mercury chemostratigraphy in order to recognize extraordinary volcanic (or other) signals, at least in the Devonian geological record. False Hg anomalies were not generated by these conventional ICP-MS determinations.

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Portal prezentujący kościonośny kajper Górnego Śląska w świetle wyników grantu N307 11703

Racki G.

Przegląd Geologiczny

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2017

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Vol. 65, nr 5

275--281

EN

The major goal of the project “The evolution of terrestrial environments of the Upper Silesian Keuper as biotopes of vertebrates”, granted for Grzegorz Racki by the Ministry of Science and Higher Education (2009-2013), was an exhaustive, integrated study of the bone-enriched middle Keuper interval in terms of stratigraphy, sedimentology, mineralogy and geochemistry. The new website “Bone-bearing Keuper of the Upper Silesia, southern Poland” (http://www.ing.pan.pl/Keuper/Bone-bearing_Keuper-1.htm)presents in English the results of this project. The significant achievements are only a starting point to a comprehensive presentation of the complex Keuper themes, jointly with an extensive repository of regional literature (above 420 full-texted publications since 1790). In addition, the main results of the grant, as well as diversity of their implications for future studies are summarized herein, with emphasis on controversial geochronological aspects in vertebrate paleontology (how many bone-rich levels?), and in a broad historical context.

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Influential Polish publications in sedimentary geology 1996-2016

Racki G.

Geological Quarterly

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2016

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Vol. 60, No. 2

537--546

EN

The list of thirty highest cited recent Polish publications (after 1995) on diverse themes resulted from study of sedimentary rocks, usually referred as sedimentary geology, is presented. The progressively successful fields include in first order large-scale palaeogeographic and lithofacies analyses in supra-regional geotectonic framework (by Golonka), and also tectonic-regional varieties of basin analysis, developed by several research groups in Cracow, Warsaw and Wrocław, in agreement with one of the leading research front in worldwide geosciences. Ecological and Integrative stratigraphic-event characteristics of sedimentary successions are another well-known Polish specialties, the best exemplified by flysch ichnology (Uchman) and Devonian studies at University of Silesia. On the other hand, sedimentary geochemistry is still in infancy in Poland, despite a big progress in last years (in particular organic topics - Marynowski). The dominance of Cracow geological school is obvious, derived from a long-lasting tradition of mostly Carpathian studies in Jaggielonian University, even if this research is well advanced as well in many other institutions in Poland. For example, a newly emerging Polish specialty in tsunami hazard studies (Szczuciński) is markedly located at Adam Mickiewicz University. Nevertheless, Carpathian and post-Palaeozoic stratigraphic-sedimentological themes were still the most popular, although simultaneously an evolution toward effective cooperation in largely international groups (also outside of Poland, especially in Ukraine) appears to be the most significant tendency in modern Polish geosciences.

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Brachiopods and stratigraphy of the Upper Devonian (Frasnian) succession of the Radlin Syncline (Holy Cross Mountains, Poland)

Baliński A., Racki G., Halamski A. T.

Acta Geologica Polonica

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2016

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Vol. 66, no. 2

125--174

EN

The lower part of the Frasnian succession in the Radlin Syncline (Kielce–Łagów Synclinorium, southern region of the Holy Cross Mountains), in the two studied successions: Józefka at Górno and (for the first time) Radlin, consists of the rhythmic marly Szydłówek Beds, the fossil-rich limestones of the Wietrznia Beds (locally) and the atypically developed, calcareous Kostomłoty Beds. The carbon isotope chemostratigraphic pattern overall corresponds well to the global Early–Middle Frasnian biogeochemical perturbation, even if the major punctata positive excursion is only fragmentarily recorded in the Kostomłoty intrashelf basin. Two brachiopod assemblages are abundantly represented in both sections: the Phlogoiderhynchus polonicus Assemblage, typical of the Szydłówek Beds, and the Biernatella lentiformis Assemblage, limited to the middle part of the Wietrznia Beds. Both are highly dominated by the index species. Twenty nine lower Frasnian brachiopod species (Craniida – 1 species, Strophomenida – 1, Productida – 2, Protorthida – 1, Orthida – 5, Pentamerida – 1, Rhynchonellida – 4, Atrypida – 4, Athyridida – 3, Spiriferida – 4, Spiriferinida – 3) are described from the Szydłówek and Wietrznia Beds. Seven new species are introduced: Skenidioides cretus Halamski sp. nov., Biernatium minus Baliński sp. nov., Monelasmina montisjosephi Baliński sp. nov., Atryparia (Costatrypa) agricolae Halamski and Baliński sp. nov., Davidsonia enmerkaris Halamski sp. nov., Leptathyris gornensis Baliński sp. nov., and Echinocoelia parva Baliński sp. nov. Davidsonia enmerkaris Halamski sp. nov. is intermediate between Davidsonia Bouchard-Chantereaux, 1849 and Rugodavidsonia Copper, 1996 and is the youngest known representative of the suborder Davidsonioidea Copper, 1996. Skenidioides cretus Halamski sp. nov. is the last representative of the genus. Statistical investigation of a large sample of Spinatrypina (Exatrypa) explanata did not confirm the existence of two dimorphic forms, coarse- and fine-ribbed. The high-diversity Biernatella lentiformis Assemblage is quite dissimilar to coeval brachiopod assemblages described heretofore from the Holy Cross Mountains region. It is interpreted as consisting of mostly parautochthonous dwellers of deep-slope muddy habitats and a local, occasionally storm-agitated, intra-basin brachiopod-crinoid-coral shoal. The fauna was adapted probably to cooler and nutrient-poor waters during an initial phase of the severe carbon cycle perturbation.

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Formacja grabowska : podstawowa jednostka litostratygraficzna kajpru Górnego Śląska

Szulc J., Racki G.

Przegląd Geologiczny

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2015

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Vol. 63, nr 2

103–-113

EN

Lithostratigraphic division of the Upper Silesian Keuper continental succession belongs to abandoned matters, even if newly-discovered sites with unique vertebrate faunas highlight an increasing request to more precise designation of their stratigraphic setting. As a result of multidisciplinary grant and with a guide use of new borehole sections, a major lithostratigraphic unit is formally proposed for the middle Keuper (i.e., above the Schilfsandstein; Stuttgart Formation in Stratigraphische Tabelle von Deutschland, 2002), based on previously inaccurately used unit, Grabowa Formation of Bilan (1976). The re-defined Formation of Variegated Mudstones and Carbonates from Grabowa includes Upper Gypsum Beds and Steinmergelkeuper in traditional scheme from Germany (=Weser and Arnstadt Formations), and generally correlates with the Norian stage. Two bone-bearing horizons (Krasiejów and Lisowice) are placed within the unit, which is completely subdivided in three members: Ozimek (mudstone-evaporate), Patoka (marly mudstone-sandstone) and WoŸniki (limestone).

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The bone–bearing Upper Triassic of Upper Silesia, southern Poland : integrated stratigraphy, facies and events – introductory remarks

Racki G., Szulc J.

Annales Societatis Geologorum Poloniae

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2015

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Vol. 85, No. 4

553--555

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Key aspects of the stratigraphy of the Upper Silesian middle Keuper, southern Poland

Szulc J., Racki G., Jewuła K.

Annales Societatis Geologorum Poloniae

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2015

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Vol. 85, No. 4

557--586

EN

The stratigraphy of the Upper Silesian Keuper, a continental, mudstone-dominated succession is poorly known, although the already renowned, newly discovered vertebrate localities highlight the growing demand for a more precise intra-regional correlation and an appropriate stratigraphic reference framework. A major lithostratigraphic unit, preliminarily proposed for the middle Keuper (i.e., above the Schilfsandstein; Stuttgart Formation in “Stratigraphische Tabelle von Deutschland”, 2002) by Szulc and Racki (2015; Przegląd Geologiczny, 63: 103– 113), is described in detail. The redefined Grabowa Variegated Mudstone-Carbonate Formation, the unit previously based on inaccurately presented information, includes the Upper Gypsum Beds and the Steinmergel-keuper in the traditional scheme from Germany (= Weser and Arnstadt formations). Three members are formally defined: the Ozimek (Mudstone-Evaporite) Member, the Patoka (Marly Mudstone-Sandstone) Member and the Woźniki (Limestone) Member. Two significant bone-bearing horizons (Krasiejów and Lisowice) are placed within the Patoka Mbr. The formation thickness in a composite, regional reference section of the Upper Silesian Keuper, based on the new Woźniki K1 and Patoka 1 well profiles, is approximately 215 m thick. The Grabowa Fm generally correlates with the Norian stage, with the base located in the undefined upper Carnian, and is topped by a major, erosive disconformity and sedimentary sequence boundary, near the Norian-Rhaetian boundary. However, hiatuses in the Silesian middle Keuper succession are located and paired with a cannibalistic type of sand-mud flat deposition, largely controlled by Early Cimmerian movements of tectonic blocks associated with the Kraków–Lubliniec shear zone.

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How many Upper Triassic bone–bearing levels are there in Upper Silesia (southern Poland)? A critical overview of stratigraphy and facies

Szulc J., Racki G., Jewuła K., Środoń J.

Annales Societatis Geologorum Poloniae

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2015

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Vol. 85, No. 4

587--626

EN

At least three widely separated bone-bearing intervals in the Upper Triassic succession of Upper Silesia, ranging in age from the Carnian to Rhaetian (i.e., in the interval of 25 Ma), are presented in papers by the Warsaw research group, led mainly by Jerzy Dzik and/or Grzegorz Niedźwiedzki. The stratigraphic arguments are reviewed for the vertebrate localities studied so far, in particular for the well-known middle Keuper sites at Krasiejów and Lipie Śląskie, to show that the previously proposed age assignments are still inadequately documented and questionable. This unreliability is exemplified by the evolving stratigraphic correlation of the fragmentary Silesian sections (8–18 m thick) with informal subsurface units from central-western Poland and with the German standard succession, ultimately not corroborated by comparison with the composite reference succession of the Upper Silesian Keuper, including new profiles (ca. 260 m thick) from the Woźniki K1 and Patoka 1 wells. Based on a multidisciplinary stratigraphic study covering consistent litho-, bio-, climato- and chemostratigraphic premises, focused on the regional reference section, two bone-bed levels only are recognized in the Patoka Marly Mudstone-Sandstone Member (= Steinmergelkeuper) of the Grabowa Formation, not very different in age (Classopollis meyeriana Palynozone; probably IVb Subzone): (1) the localized Krasiejów bone breccia level (early Norian in age) in the Opole region, and (2) the far more widely distributed Lisowice bone-bearing level (middle Norian) in a vast alluvial plain (braided to anastomosing river system) during the Eo-Cimmerian tectonic-pluvial episode. As a consequence of the principal uncertainties and controversies in Upper Triassic terrestrial stratigraphy, this is still a somewhat preliminary inference. Typical skeletal concentra- tions of a combined hydraulic/sedimentologic type, related to fluvial processes, are common in the Upper Silesian Fossil-Lagerstätten, although factors governing preservation are probably important, as well.

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Comparative oxygen and carbon isotopic records of Miocene and recent lacustrine unionid bivalves from Poland

Błażejowski B., Racki G., Gieszcz P., Małkowski K., Kin A., Krzywiecka K.

Geological Quarterly

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2013

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Vol. 57, No. 1

113–-122

EN

The δ13C and δ18O isotope data from both fossil (Miocene) and modern freshwater bivalve shells of family Unionidae from Poland (species Margaritifera flabellatiformis and Unio tumidus, respectively) show a similar, truncated sinusoidal pattern.. The isotopic profiles of the whole shell are visibly marked by three growth stages, linked with a progressive loss of environmental record because of declining intra-annual biocarbonate accretion rate. The juvenile and gerontic phases exhibit generally more positive and stable (plateau) isotopic pattern than the mid-age stage. An increasing δ13C trend is typical for the final life stage, likely influenced by nutrient overloading, reversing the tendency towards δ13C depletion throughout the individual’s life induced by metabolic processes. Due to the progressive loss of environmental signals through ontogeny, these initial and final isotopic profile segments probably correspond to, respectively, an instant signature of the first season growth, and a multiyear value set of summer maxima during geriatric stage. Vague seasonal cyclic record is the striking feature of the mid-age δ18O and δ13C profile slices. In case of low-amplitude δ18O curve, this is probably promoted by a sensitivity of the lake ecosystem to many dynamic intra-annual factors affecting water budget balance. This consistent signature mode seems to be typical for lake-dwelling unionid shells at least since Miocene from different climatic zones, as confirmed by coeval lacustrine low-latitude mussels from Amazonia. Thus, this isotope record is relevant to obtain information on the habitat and life cycle of the fossil freshwater bivalves, as well as could help understand modern environmental change.

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Ewolucja środowisk lądowych kajpru Górnego Śląska jako biotopów kręgowców-nowy projekt badawczy

Racki G.

Przegląd Geologiczny

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2010

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Vol. 58, nr 2

124-126

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Proliferation of abnormal palynoflora during the end-Devonian biotic crisis

Filipiak P., Racki G.

Geological Quarterly

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2010

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Vol. 54, No 1

1-14

EN

The dispersed miospore assemblage of the Retispora lepidophyta-Verrucosisporites nitidus (LN) Zone from the Holy Cross Mountains(Poland) is marked by enrichment (above 4%) in abnormal spore morphotypes during a terrestrial flora turnover close to the Devonian-Carboniferous boundary, recorded just above the Hangenberg Black Shale level. Incomplete and complete tetrads represent mostly Vallatisporites spp., supplemented by Grandispora, Retusotriletes and Apiculiretusispora. Additional peculiar morphotypes, marked byanomalous overall shape and ornamentation, are interpreted as mutated varieties of Vallatisporites based on intermediate morphologicalstages, connecting them with this well known genus. This relatively high aberrant palynomorph frequency is accompanied by volcanicash intercalations, as well as by charcoal debris and polycyclic aromatic biomarkers indicative of forest wildfire. Thus, the anomalousspore morphology could reflect the mutagenic effect of regional acidification due to explosive volcanism. However, palynological literature data from NW France and Canada highlight the possibility of a supra-regional mutated miospore signal near the Devonian-Carboniferous boundary, and there is need for high-resolution studies of the LN Zone to examine this. The end-Permian scenario of abnormalfloral growth in immensely stressed habitats may therefore apply to other potentially volcanically-induced biotic turnovers.

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Very large stromatoporoid indicating Early Frasnian reef core (Holy Cross Mts., Poland)

Racki G., Sobstel M.

Geological Quarterly

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2004

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Vol. 48, No 1

83--88

EN

A large stromatoporoid Actinostroma cf. crassepilatum Lecompte, 1951, at least 8.5 m in diameter and 0.85 m in height, occurs in the Śluchowice quarry in Kielce, Holy Cross Mountains. This sponge occurs in growth position within Early Frasnian (transitans Zone) intraclast-rich reef-rubble deposits. A unique preservation of the reef-builder close to a reef core is implied for the northern flank of the developing Dyminy Reef during its maximum expansion northward into the Kostomłoty intrashelf basin.

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Geochemical and ecological aspects of lower Frasnian pyrite-ammonoid level at Kostomłoty (Holy Cross Mountains, Poland)

Racki G., Piechota A., Bond D., Wignall P. B.

Geological Quarterly

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2004

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Vol. 48, No 3

267--282

EN

The lower Frasnian (transitans Zone with Ancyrodella priamosica = MN 4 Zone) rhythmic basin succession of marly limestones and shales (upper Szydłówek Beds) at Kostomłoty, western Holy CrossMts., Central Poland, contains a record of the transgressive-hypoxic Timan Event in this drowned part of southern Laurussian shelf. The unique facies consists of organic-rich marly shales and a distinctive pyritic, goniatite level, 1.6mthick. The faunal assemblage is dominated by pyritized shells of diminutivemollusks with cephalopods (including goniatites Epitornoceras and Acanthoclymenia), buchioline bivalves (Glyptohallicardia) and styliolinids. This interval is marked by moderately low Th/U ratios and pyrite framboid size distributions suggestive of dysoxic rather than permanent euxinic conditions. The scarcity of infauna and bioturbation resulted in finely laminated sedimentary fabrics, as well as the low diversity of the presumed pioneer benthos (mostly brachiopods). In the topmost part of the Szydłówek Beds, distinguished by the Styliolina coquina interbedded between limestone-biodetrital layers, the above geochemical proxies and C-isotope positive shift indicate a tendency to somewhat increased bottom oxygen deficiency and higher carbon burial rate linked with a bloom of pelagic biota during high-productivity pulse. The geochemical and community changes are a complex regional record of the initial phase of a major perturbation in the earth-ocean system during a phase of intermittently rising sea level in the early to middle Frasnian, and associated with the highest positive C-isotope ratios of the Devonian.

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What is hot in sedimentary research over the millenium crossroad?

Racki G.

Acta Geologica Polonica

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2002

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Vol. 52, nr 4

577-584

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Late Devonian radiolarians and sponge spicules from Poland and palaeoenvironmental implications

Vishnevskaya V., Pisera A., Racki G.

Biuletyn Państwowego Instytutu Geologicznego

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2001

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nr 396

162-163

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Tektoniczne a eustatyczne uwarunkowania rozwoju sedymentacji dewonu świętokrzyskiego

Racki G., Narkiewicz M.

Przegląd Geologiczny

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2000

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Vol. 48, nr 1

65-76

PL

Ranga zdarzeń tektonicznych w dewonie świętokrzyskim jest wciąż trudna do sprecyzowania, ale wydaje się drugoplanowa. Nie ma świadectw " bretońskich " deformacji tektonicznych w końcu dewonu i uprzednio eksponowana rola tej "fazy " może ograniczać się do pulsu póżnofrańskiej subsydencji tektonicznej i ruchów blokowych, modyfikujących lokalnie zapis fluktuacji eustatycznych w szeroko rozumianym interwale przejściowym franu i famenu. Związki tego ożywienia tektonicznego na obszarze świętokrzyskim z póżnodewońskąprzebudowąplatformy wschodnioeuropejskiej (inicjacją ryftuprypecko-donieckiego i rozwojem rowu lubelskiego) są prawdopodobne, ale ich korelacja wymaga dalszego postępu w badaniach stratygraficznych na obu tych obszarach.

EN

Documented evidence of synsedimentary tectonics in the Devonian of the Holy Cross Mts. in most cases indicates limited magnitude of deformations leading to modification of the sedimentary record merely in a local scale. In contrast, the events interpreted as eustatic (including i.a. backstepping of the carbonate platform) have a widespread regional record. The tectonic subsidence analysis confirms differences in a development of the Łysogóry and Kielce regions, although both regions reveal very similar scenario of the "post-Caledonian " subsidence, differing mainly in the rates and total amount of the Devonian subsidence. The latter differences may be ascribed to contrasts in a deep structure ofcrustal blocks underlying both regions, separated by the Holy Cross Fault, and responding differently to a regional stress pattern, probably in an extensional regime. Although the importance of tectonic events in the Devonian of the Holy Cross Mts. is still difficult to ascertain, it appears rather subordinate in view of available observations. So far, there is no evidence of the "Bretonnian " tectonic deformations in the latest Devonian. The role of this ,, phase", previously stressed in several publications, may be limited to the probable small pulse of the late Frasnian subsidence and small-scale block movements locally modifying the record of eustatic fluctuations in the wide interval of the Frasnian-Famennian transition. The relationship between these tectonic phenomena and the Late Devonian structural rearrangement of the East European Craton, including initiation of the Pripyat-Donets Rift and development of the Lublin Trough is probable but requires further refinement of a stratigraphic correlation between the discussed areas.

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Proces wymierania i odradzania się faun ramienionogowych a kryzys na granicy fran-famen

Baliński A., Racki G.

Przegląd Geologiczny

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1999

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Vol. 47, nr 4

373-378

PL

Dobrze poznana sukcesja zespołów ramienionogów w późnym dewonie antykliny Dębnika (południowa Polska) umożliwia szczegółowe prześledzenie zjawiska wielkiego kryzysu biotycznego, jakie miało miejsce na granicy fran-famen. Największe zróżnicowanie taksonomiczne frańskich ramienionogów na tym obszarze obserwuje się w poziomach P. punctata–P. hassi (20 gatunków). W młodszych poziomach franu zróżnicowanie taksonomiczne ramienionogów stopniowo maleje aby osiągnąć minimum przy granicy fran-famen. Zespół ramienionogów po wielkim wymieraniu zdominowany jest przez zaledwie dwa zdrobniałe gatunki reprezentujące rynchonellidy i spiriferidy. Począwszy od poziomu P. crepida zaznacza się intensywny proces odbudowy fauny ramienionogów, zdominowanej przez cyrtospiriferidy, atyrididy i produktellidy. W młodszym famenie obserwuje się jednak ponowny spadek zróżnicowania, w miarę nasilania się procesów regresywnych. Podobną dynamikę ewolucyjną ramienionogów w pobliżu granicy fran-famen, a zwłaszcza procesu repopulacji i redywersyfikacji, obserwuje się w Górach Świętokrzyskich. W poziomach P. crepida-P. rhomboidea ramienionogi osiągają największe zróżnicowanie taksonomiczne dla famenu. Ogólny skład pionierskich zespołów pokryzysowych z wczesnego famenu południowej Polski sugeruje pokrewieństwo z płytkowodnymi frańskimi faunami wewnętrznych szelfów węglanowych i środowisk deltowych oraz częściowo - z głębokowodnej biofacji rynchonellidowej.

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Kontrowersje wokół przyczyn wielkich katastrof ekologicznych

Racki G.

Przegląd Geologiczny

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1999

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Vol. 47, nr 4

343-348

PL

Trwająca blisko 20 lat (od odkrycia anomalii irydowej) polemika nad przyczynami wielkich katastrof ekologicznych w historii Ziemi między zwolennikami koncepcji upadku gigantycznego bolidu i kataklizmu wulkanicznego doprowadziła do istotnych modyfikacji pierwotnych paradygmatów. Do najbardziej istotnych należą modele kryzysów biotycznych ("kroczących" wymierań) wskutek wielokrotnej i (lub) skośnej kolizji z obiektem pozaziemskim, zwłaszcza kometą, jak też koncepcje nawiązujące do dalekosiężnych skutków ekosystemowych erupcji superpióropusza płaszcza czy wielkoskalowego ryftingu. Najbardziej perspektywiczne są scenariusze wymierań odwołujące się albo wyłącznie do ziemskich procesów, zwłaszcza oceanograficznych i klimatycznych (np. intensywnie propagowany model transgresji/anoksji), z coraz lepiej rozumianą rolą zjawisk wulkaniczno-hydrotermalnych, albo koncepcje "mieszane" - z mniejszym lub większym udziałem katastrof kosmicznych. Ta ostatnia hipoteza jest szczególnie przydatna dla wyjaśnienia wymierania z końca kredy, gdy doszło do nałożenia się skutków obu rodzajów kataklizmów o zasięgu globalnym. Dalsze kompleksowe badania o coraz bardziej interdyscyplinarnym charakterze, nawiązujące do zdarzeń kredowych i kenozoicznych jako swoistych reperów, są konieczne dla zrozumienia wielu zagadek historii biosfery, szczególnie w paleozoiku.

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Biostratygraficzne i geochemiczne problemy identyfikacji granicy fran-famen w południowej Polsce

Racki G., Matyja H., Racka M., Joachimski M.

Przegląd Geologiczny

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1999

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Vol. 47, nr 4

369-372

PL

W trakcie dokładnych badań konodontowych reperowych profili pogranicza fran-famen (F-F) w Górach Świętokrzyskich (Kowala) i rejonie Krakowa (Dębnik) natrafiono na trudności w biostratygraficznym rozpoznaniu tej naturalnej granicy pięter, odpowiadającej zdarzeniu wielkiego wymierania, jak i dokumentowaniu jej geochemicznej specyfiki. Sukcesja zespołów konodontowych przez krytyczny poziom F-F wykazuje zaskakująco stopniowy charakter, manifestujący się głównie we współwystępowaniu typowo frańskich palmatolepidów i ancyrodellidów z diagnostycznym dla famenu, bardzo zmiennym gatunkiem Palmatolepis triangularis (obejmującym morfotyp praetriangularis). Profile pierwiastków śladowych oraz izotopów węgla, tak węglanowego, jak i organicznego, wskazują na przeważnie "spokojny", pozbawiony ważniejszych zdarzeń interwał pogranicza F-F sensu stricto, choć być może odpowiadający najwyższym poziomom produktywności. Największe zmiany oceanograficzne miały miejsce w pierwszej fazie sedymentacji górnego poziomu Kellwasser w dobie linguiformis, a więc przed kryzysem konodontów. Dane te wzmacniają scenariusz rozciągniętego w czasie, złożonego kryzysu biotycznego wskutek oddziaływania czynników ziemskich, ale nie globalnej katastrofy kosmicznej.