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    Tytuł:
    Early-Middle Frasnian cyrtospiriferid brachiopods from the East European Platform
    Autorzy:
    Sokiran, E V
    Powiązania:
    https://bibliotekanauki.pl/articles/21097.pdf
    Data publikacji:
    2006
    Wydawca:
    Polska Akademia Nauk. Instytut Paleobiologii PAN
    Tematy:
    Early-Middle Frasnian
    Frasnian
    cyrtospiriferid brachiopod
    brachiopod
    East European Platform
    paleontology
    Russia
    Brachiopoda
    Cyrtospiriferidae
    Opis:
    The cyrtospiriferids are among the most important fossils in the Frasnian strata of the East European Platform (EEP). During the Early Frasnian (Palmatolepis falsiovalis Zone) the numerous and morphologically distinct Uchtospiriferinae, accompanied by very scarce Cyrtospiriferinae, are known from South Timan. The mass appearance of cyrtospiriferins on the platform at the beginning of the Middle Frasnian is linked with significant sea−level rise of Devonian Transgression−Regression (T−R) cycle IIc. At that interval these brachiopods attain their highest diversity of the entire Frasnian. The Early Frasnian type species of the genus Uchtospirifer is here revised, and subfamily Uchtospiriferinae re−established. Cyrtospirifer schelonicus, C. rudkinensis, C. mylaensis sp. nov., and C. tenticulum are described from the Middle Frasnian of NW and central regions of EEP and Middle Timan.
    Źródło:
    Acta Palaeontologica Polonica; 2006, 51, 4; 759-772
    0567-7920
    Pojawia się w:
    Acta Palaeontologica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Conodont ecology in the Early-Middle Frasnian transition on the South Polish carbonate shelf
    Autorzy:
    Sobstel, M
    Makowska-Haftka, M.
    Racki, G.
    Powiązania:
    https://bibliotekanauki.pl/articles/23066.pdf
    Data publikacji:
    2006
    Wydawca:
    Polska Akademia Nauk. Instytut Paleobiologii PAN
    Tematy:
    conodont
    ecology
    Early-Middle Frasnian
    Frasnian
    Southern Poland
    carbonate shelf
    paleoecology
    Holy Cross Mountains
    deposit
    Palmatolepis transitans
    Palmatolepis punctata
    Opis:
    Well exposed Early–Middle Frasnian (E–MF, Palmatolepis transitans to Palmatolepis punctata zonal interval) deposits of the Holy Cross Mountains, in particular the reference Wietrznia section at Kielce, were studied in terms of conodont biofacies dynamics. Frequency of the conodont elements has been controlled mostly by depositional rate in hemipelagic muddy lithofacies and post−mortem gravity sorting during lateral redeposition in storm−generated, talus−like and encrinite layers. The conodont assemblages are dominated by a highly varying proportion of polygnathid, icriodontid, and ancyrodellid fauna. Major biofacies turnovers coincided with the deepening pulses corresponding to Timan, Middlesex, and early Rhinestreet global events. Trends in the conodont dynamics, mortality, and diversity point that the biotic shifts also coincide with the large−scale δ¹³C excursions as a record of changing trophic conditions during the major biogeochemical perturbation. A gradual decline of the Early Frasnian Ancyrodella reef−dwelling community correlates with the minor positive and succeeding larger negative δ¹³C excursion, and this is paired with a replacement by, mostly sparse, polygnathid and polygnathid−icriodontid biofacies, as well as with a short−term Belodella acme in mud−mounds areas. The distinctive habitat deterioration in pelagic and reef ecosystems is broadly correlative with the Domanik Crisis. The progressive biofacies unification is a conodont response to onset of the prolonged (ca. 0.5 Ma) δ¹³C enrichment, probably linked with high−stress life conditions due to eutrophication and partly anoxic regimes. A negative carbon isotope excursion in the late Pamatolepis punctata Zone is marked by the second major biofacies turning point during the Rhinestreet transgression, as recorded primarily in a final mesotaxid extinction, and highlighted also by decrease of conodont size and increased mortality of juveniles. After stabilization of δ¹³C values and a return to the background level across the Palmatolepis punctata–Palmatolepis hassi zonal transition, renewed biofacies diversification, in particular re−appearance of reef−related ancyrodellid fauna, took place. In addition, a large−scale migration event among palmatolepids and polygnathids during sea−level rise, mainly from the East European Platform, characterised this Middle Frasnian interval.
    Źródło:
    Acta Palaeontologica Polonica; 2006, 51, 4; 719-746
    0567-7920
    Pojawia się w:
    Acta Palaeontologica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Early-Middle Frasnian transition: Biotic response to a major perturbation of the global carbon budget
    Autorzy:
    Balinski, A
    Olempska, E.
    Racki, G.
    Powiązania:
    https://bibliotekanauki.pl/articles/22463.pdf
    Data publikacji:
    2006
    Wydawca:
    Polska Akademia Nauk. Instytut Paleobiologii PAN
    Tematy:
    Early-Middle Frasnian
    Frasnian
    biotic response
    perturbation
    global carbon budget
    Źródło:
    Acta Palaeontologica Polonica; 2006, 51, 4; 606-608
    0567-7920
    Pojawia się w:
    Acta Palaeontologica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Gastropod succession across the Early-Middle Frasnian transition in the Holy Cross Mountains, southern Poland
    Autorzy:
    Krawczynski, W
    Powiązania:
    https://bibliotekanauki.pl/articles/21568.pdf
    Data publikacji:
    2006
    Wydawca:
    Polska Akademia Nauk. Instytut Paleobiologii PAN
    Tematy:
    paleontology
    gastropod succession
    Early-Middle Frasnian
    Frasnian
    transition
    Holy Cross Mountains
    Southern Poland
    Polska
    Gastropoda
    Eotomariidae
    Elasmonematidae
    bioevent
    Devonian
    Opis:
    Gastropod response to a marked carbon isotopic geochemical anomaly across the Early–Middle Frasnian transition (Palmatolepis transitans–Palmatolepis punctata conodont zones) has been analysed along the southern Laurussian shelf, mainly within the Dyminy Reef in the Holy Cross Mountains. Gastropods are represented by three reefal associations (Kowalatrochus sanctacrucensis, Euryzone kielcensis, and Grabinopsis guerichi associations), and an impoverished open−shelf Straparollus laevis assemblage. The most severe diversity crisis is connected to the disappearance of local low−energy muddy habitats, as a result of a transgressive pulse (Middlesex Event) and benthic habitat changes tied to strongly fluctuating carbon cycling; this has been observed at the highly diverse Kadzielnia−type assemblage. Fifteen taxa have been recognised in this distinctive Early Frasnian mud−mound association, including six (probably endemics), which are unknown from the Middle Frasnian. The disappearance of three relict Givetian species (Euryzone delphinuloides, Straparollus laevis, and Goniasma? zarecznyi) is also recorded. Other species probably migrated into the shallower water part of Dyminy Reef and persisted in the Middle and Late Frasnian. The Middlesex Event and the earlier major biogeochemical perturbation seem to have less serious effects for evolution of gastropods in the Polish−Moravian part of the Laurussia shelf than the catastrophic Frasnian–Famennian extinction. Two new taxa are described: Frydiella kaimi gen. et sp. nov. (Eotomariidae) and Heidelbergeria czarnieckii gen. et sp. nov. (Elasmonematidae).
    Źródło:
    Acta Palaeontologica Polonica; 2006, 51, 4; 679-693
    0567-7920
    Pojawia się w:
    Acta Palaeontologica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Benthic ostracods from the Early-Middle Frasnian transition in the north-western East European Platform, Russia
    Autorzy:
    Evdokimova, I O
    Powiązania:
    https://bibliotekanauki.pl/articles/21796.pdf
    Data publikacji:
    2006
    Wydawca:
    Polska Akademia Nauk. Instytut Paleobiologii PAN
    Tematy:
    benthic ostracod
    ostracod
    Early-Middle Frasnian
    Frasnian
    paleontology
    East European Platform
    Russia
    Ostracoda
    Main Devonian Field
    Opis:
    Pronounced changes in benthic ostracod associations in the north−west part of the East European Platform, across the Early–Middle Frasnian (Devonian) transition, track a marine transgression event. More than 80 ostracod species belonging to the Eifelian Mega−Assemblage were recorded. Cavellinidae and Acratiidae generally dominate the Early Frasnian Sargaevo Horizon. Middle Frasnian ostracod associations of the Semiluki Horizon are more diverse and are characterised by different dominant both geographically and stratigraphically, resulting from significant palaeo−basin bottom relief and benthic biotope differentiation. The ostracod associations are indicative of very shallow, well oxygenated semi−restricted epeiric environment, with occasional marine influence, alternating with short periods of open shelf conditions. The relative abundance of ostracod species in the different associations, and faunal diversity indices, show considerable variations throughout the Early–Middle Frasnian, and suggest a less restricted position within an intra−platform setting in the Middle Frasnian, relative to a more restricted ostracod habitat in the Early Frasnian. The succession of Early–Middle Frasnian micro−benthic associations within the Main Devonian Field seems to be of a regional scale, and resulted from a marine regression−transgression couplet, corresponding to eustatic cycles IIb–IIc. This was paired with synsedimentary tectonic subsidence in adjacent areas of the north−east East European Platform, progressively improving marine water circulation in the extremely shallow−water shelf seas.
    Źródło:
    Acta Palaeontologica Polonica; 2006, 51, 4; 773-778
    0567-7920
    Pojawia się w:
    Acta Palaeontologica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Conodont-based event stratigraphy of the Early-Middle Frasnian transition on the South Polish carbonate shelf
    Autorzy:
    Pisarzowska, A
    Sobstel, M.
    Racki, G.
    Powiązania:
    https://bibliotekanauki.pl/articles/22673.pdf
    Data publikacji:
    2006
    Wydawca:
    Polska Akademia Nauk. Instytut Paleobiologii PAN
    Tematy:
    conodont association
    stratigraphy
    Early-Middle Frasnian
    Frasnian
    Polska
    carbonate shelf
    biostratigraphy
    carbon isotope
    paleoecology
    Devonian
    Palmatolepis transitans
    Palmatolepis punctata
    Opis:
    Early to Middle Frasnian (E–MF) epicontinental sequences are investigated in five representative localities of the Holy Cross Mountains and Cracow region, with emphasis on conodont biostratigraphy, to evaluate the regional stratigraphic and biotic context of a major biogeochemical perturbation in global carbon cycling. Conodont associations from the Palmatolepis transitans to Palmatolepis punctata Zone boundary beds are dominated by the shallow−water polygnathid and ancyrodellid fauna in the South Polish epicontinental successions, and first appearances of index palmatolepid species are delayed due to facies control of pelagic environments during intermittent drowning of the carbonate shelf. Thus, identification of the zonal boundary is based mainly on species of Ancyrodella, and five distinctive ancyrodellid levels in the succession across the E–MF interval enable refined correlation of the sections studied, especially when paired with chemostratigraphic proxies. Prominent conodont biofacies shifts coincided with eustatic deepening, which is correlated with the Timan, Middlesex, and early Rhinestreet events, respectively. Trends in the conodont dynamics, mortality and diversity, partly replicated by the benthic biota (especially shelly faunas and crinoids), indicate that the faunal turnovers correlate also with the main δ¹³C excursions and related changes in trophic conditions. The E–MF transitional interval, marked by short−term sea−level fluctuations, is distinguished by a change from relatively diversified biofacies to more homogenous, mostly impoverished faunas. The latter change is a biotic response to the beginning of a prolonged (ca. 0.5 Ma) positive δ¹³C anomaly, probably paired with unsteady eutrophic and partly anoxic regimes. The late Pa. punctata Zone negative carbon isotope anomaly is synchronous with the second large−scale pelagic biofacies remodelling, including mesotaxid extinction. A stabilization of the carbon cycle and its return to normal background values at the start of the Early Palmatolepis hassi Zone coincide with conodont biofacies diversification and recovery of reef−related biofacies. With the exception of collapsed, endemic Kadzielnia−type mud−mound biota and a moderate biodiversity depletion due to overall ecosystem stagnation, no significant extinction events can be demonstrated, even if the large−scale changes in carbon cycling during the E–MF timespan are of higher−amplitude than the celebrated carbon isotopic anomalies related to the Frasnian–Famennian mass extinction. Thus, this regional succession in detail confirms that the large−scale punctata Isotopic Event (= Pa. punctata Event) is correlated neither with catastrophic enviromental nor radical biotic changes.
    Źródło:
    Acta Palaeontologica Polonica; 2006, 51, 4; 609-646
    0567-7920
    Pojawia się w:
    Acta Palaeontologica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Brachiopods and their response to the Early-Middle Frasnian biogeochemical perturbations on the South Polish carbonate shelf
    Autorzy:
    Balinski, A
    Powiązania:
    https://bibliotekanauki.pl/articles/20277.pdf
    Data publikacji:
    2006
    Wydawca:
    Polska Akademia Nauk. Instytut Paleobiologii PAN
    Tematy:
    brachiopod
    brachiopod response
    paleontology
    Early-Middle Frasnian
    Frasnian
    biogeochemical perturbation
    Southern Poland
    Polska
    carbonate shelf
    Brachiopoda
    Flabellulirostrum
    Thomasaria
    carbon isotope
    diversity dynamics
    Opis:
    The brachiopod faunas from deposits recording the Early–Middle Frasnian transition of Poland are poorly known. The present report describes these faunas that were recovered from Wietrznia and Kostomłoty (Holy Cross Mountains) and Dębnik (Silesian−Cracow Upland) regions positioned on the southern Polish carbonate shelf. The brachiopod distribution was analysed relative to a significant δ¹³C excursion, referred recently to as Palmatolepis punctata Event. The sporadic occurrence of brachiopods at Dębnik makes it difficult to analyse the biotic response to this geochemical anomaly. However, higher brachiopod frequency in the topmost part of the section coincides with a gradual decrease of δ¹³C down to the Frasnian background values. At two studied sections at Wietrznia the greatest taxonomic diversity and abundance of brachiopods (Flabellulirostrum–Coeloterorhynchus assemblage) are confined to the Palmatolepis transitans Zone. In the following Pa. punctata Zone brachiopods are rare (Biernatella lentiformis assemblage) or absent, which suggests a serious deterioration of the environmental conditions linked probably with periods of benthic anoxia−dysoxia and oligotrophic conditions in the basin. In two Kostomłoty sections brachiopods faunas of this age are members of the mostly monospecific rhynchonellid−dominated Phlogoiderhynchus polonicus assemblage which inhabited deeper−water environments characteristic of intrashelf oxygen−depleted basins of ŁysogóryKostomłoty region. In some horizons large shells of P. polonicus were frequently colonised by discinoid Romerella? sp. Among 28 species described in this report new forms include: Flabellulirostrum kielcensis sp. nov., F. rackii sp. nov., and Thomasaria ventosa sp. nov.
    Źródło:
    Acta Palaeontologica Polonica; 2006, 51, 4; 647-678
    0567-7920
    Pojawia się w:
    Acta Palaeontologica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Faunal and facies changes at the Early-Middle Frasnian boundary in the north-western East European platform
    Autorzy:
    Zhuravlev, A V
    Sokiran, E.V.
    Evdokimova, I.O.
    Dorofeeva, L.A.
    Rusetskaya, G.A.
    Malkowski, K.
    Powiązania:
    https://bibliotekanauki.pl/articles/20261.pdf
    Data publikacji:
    2006
    Wydawca:
    Polska Akademia Nauk. Instytut Paleobiologii PAN
    Tematy:
    fauna change
    Early-Middle Frasnian
    East European Platform
    Conodonta
    Brachiopoda
    Ostracoda
    correlation
    carbon isotope
    Frasnian
    Main Devonian Field
    Opis:
    Multidisciplinary study of the Early–Middle Frasnian boundary in the north−western East European Platform (Main Devonian Field) allows evaluation of changes in facies, brachiopod, ostracod, and conodont associations, as well as carbon isotope composition. Brachiopod and ostracod faunas, characterized by predominance of rhynchonellids, spiriferids, podocopids, and platycopids in the Early Frasnian, and by predominance of spiriferids, palaeocopids, and kloedenellocopids in the Middle Frasinan, demonstrate significant changes in dominance and diversity likely caused by regressiontransgression couplets in the extremely shallow−water environment. Changes in diversity of the conodont associations, represented mainly by shallow−water polygnathids and spathognathids, are controlled by sea−level fluctuations as well; however significant evolutionary turnover is absent. Deepening pulses lead to an increasing in diversity of both the benthic and nectic groups, whilst regressions cause diversity fall due to progressive habitat reduction. Most prominent decreasing in the fauna diversity is observed in the late Early Frasnian (Dubnik time) coinciding with the regressive phase of the Late Givetian to Early Frasnian eustatic cycle. Positive−negative δ¹³C excursion, detected in brachiopod calcite from the early interval of the Middle Frasnian, can be correlated with global isotopic perturbations near the Frasnian substage boundary: the positive 2.6‰ δ¹³C excursion is probably linked with enhanced primary production in high−nutrient regimes in the epeiric sea.
    Źródło:
    Acta Palaeontologica Polonica; 2006, 51, 4; 747-758
    0567-7920
    Pojawia się w:
    Acta Palaeontologica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Crinoid and ostracod succesion within the Early-Middle Frasnian interval in the Wietrznia quarry, Holy Cross Mountains, Poland
    Autorzy:
    Gluchowski, E
    Casier, J.G.
    Olempska, E.
    Powiązania:
    https://bibliotekanauki.pl/articles/20148.pdf
    Data publikacji:
    2006
    Wydawca:
    Polska Akademia Nauk. Instytut Paleobiologii PAN
    Tematy:
    paleontology
    crinoid succession
    ostracod succesion
    Early-Middle Frasnian
    Frasnian
    Wietrznia quarry
    Holy Cross Mountains
    Polska
    Crinoidea
    Ostracoda
    Palmatolepis transitans
    Palmatolepis punctata
    Opis:
    Early–Middle Frasnian ostracods and crinoids from Wietrznia in the Northern Kielce subregion of the Holy Cross area were analyzed. Twenty three ostracod species assigned to thirteen named genera, as well as eighteen crinoid species including the representatives of fifteen stem−based taxa were distinguished. For most of the species open nomenclature is applied. The composition of ostracod assemblage changes from moderately diverse in the lower part of the Palmatolepis transitans Zone to poorly diverse in its higher part. Lack of ostracods in the uppermost part of the Pa. transitans Zone and in the Palmatolepis punctata Zone is noted. The crinoid distribution pattern comprises the interval of relatively high diversity, interrupted in the uppermost part of the Pa. transitans Zone, and the interval of temporary recovery in the lower Pa. punctata Zone. Such distribution patterns point to deterioration of environmental conditions across the Early–Middle Frasnian transition, coinciding with a large−scale C−isotopic perturbation superimposed on intermittent, two−step eustatic sea level rise. On the other hand, impoverished, surviving crinoid faunas and absence of ostracods in the Pa. punctata Zone indicate the overall long−term deterioration of life conditions through the major C−isotope anomaly time span. However, this may also result from synsedimentary tectonic pulses, causing block movements and large−scale resedimentation phenomena on the northern slope of the Dyminy Reef during the basal Middle Frasnian sea level rise.
    Źródło:
    Acta Palaeontologica Polonica; 2006, 51, 4; 695-706
    0567-7920
    Pojawia się w:
    Acta Palaeontologica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Early and Middle Frasnian brachiopod faunas and turnover on the South China shelf
    Autorzy:
    Ma, X -P
    Becker, R.T.
    Li, H.
    Sun, Y.-Y.
    Powiązania:
    https://bibliotekanauki.pl/articles/21029.pdf
    Data publikacji:
    2006
    Wydawca:
    Polska Akademia Nauk. Instytut Paleobiologii PAN
    Tematy:
    Early Frasnian
    Middle Frasnian
    Frasnian
    paleontology
    brachiopod fauna
    South China shelf
    Devonian
    Brachiopoda
    Cyrtospirifer
    faunal turnover
    Opis:
    The first appearance of the brachiopod Cyrtospirifer and related forms in the Late Devonian of South China significantly postdates the beginning of the Frasnian and the entry of the group in other parts of the world. Scattered data from different sections suggest that its first entry, associated with the emergence of other plicate spiriferids, such as theodossid and conispiriferid brachiopods, was late in the Middle Frasnian. At the same time, many rhynchonellids disappeared or became extinct locally in South China. This brachiopod faunal overturn near the Palmatolepis punctata–Early Pa. hassi zonal boundary is the most significant event in the Early–Middle Frasnian of South China, characterized by about a 35% loss of existing species and the flourishing of the plicate spiriferids, which was coeval with the end of a major biogeochemical perturbation recently recognized in the Pa. punctata Zone. By contrast, atrypid brachiopods do not seem to show any significant diversity change. The brachiopod faunal change was probably related to a (local?) transgressive event in South China, which also brought new pelagic faunas northwards into some intra−shelf deeper water areas, such as the Shetianqiao area in central Hunan Province. Fifteen brachiopod species are described and illustrated, which include some taxa that are first recorded or recognized in South China, e.g., the spiriferid Pyramidaspirifer, which is now known from both North America and South China. One new species, Desquamatia qiziqiaoensis, is erected.
    Źródło:
    Acta Palaeontologica Polonica; 2006, 51, 4; 789-812
    0567-7920
    Pojawia się w:
    Acta Palaeontologica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Ostracods and facies of the Early and Middle Frasnian at Devils Gate in Nevada: Relationship to the Alamo Event
    Autorzy:
    Casier, J -G
    Berra, I.
    Olempska, E.
    Sandberg, C.
    Preat, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/23394.pdf
    Data publikacji:
    2006
    Wydawca:
    Polska Akademia Nauk. Instytut Paleobiologii PAN
    Tematy:
    ostracod
    Early Frasnian
    Frasnian
    Middle Frasnian
    Nevada
    relationship
    Alamo Event
    Ostracoda
    conodont
    sedimentology
    paleoecology
    Opis:
    In order to document the Alamo Event and to investigate its influence on shallow−marine environments, we undertook a study of ostracods, conodonts, and analysis of the sedimentology of the lower member of the type Devils Gate Limestone. Six major carbonate microfacies (MF1–MF6) ranging from open−marine environments below storm wave base to pre−evaporitic supratidal lagoons were recognized. The sedimentological study detected no important sedimentological changes during the Alamo Event; only an influx of detrital material and lithoclasts indicate that an unusual event had occurred. Ostracods are generally rare or absent in the lower member of the Devils Gate Limestone, and only 2,000 carapaces, valves and fragments were extracted; from these some 26 taxa were identified. Two new species, Voronina? eureka and Serenida dorsoplicata are proposed. The ostracods belong to the Eifelian Mega−Assemblage and their distribution was influenced by strong salinity variations. Because of the rarity and low diversity of ostracods and conodonts in samples collected from the lower part of the lower member of the Devils Gate Limestone it is not adequate to demonstrate conclusively an extinction event close to the Alamo Event Bed. Nevertheless the greater abundance and diversity of ostracods above this bed seems to indicate that the Alamo Event did not result in significant extinction of ostracod taxa in this shallow water setting. The ostracod fauna present in the lower member of the Devils Gate Limestone suggests faunal exchanges between Nevada and the Russian Platform via the Western Canadian platform.
    Źródło:
    Acta Palaeontologica Polonica; 2006, 51, 4; 813-828
    0567-7920
    Pojawia się w:
    Acta Palaeontologica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Growth in early species of the conodont Ancyrodella and implications for correlation of the Middle-Upper Devonian boundary
    Autorzy:
    Miller, C.G.
    Powiązania:
    https://bibliotekanauki.pl/articles/2059511.pdf
    Data publikacji:
    2007
    Wydawca:
    Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
    Tematy:
    conodonts
    Devonian
    Givetian
    Frasnian
    Ancyrodella
    ontogeny
    Opis:
    The first occurrence of the conodont Ancyrodella rotundiloba has been used extensively for correlating the Middle-Up per Devonian (Givetian-Frasnian) boundary in sections worldwide despite many arguments as to its precise taxonomic definition. These arguments are summarised herein and three ontogenetic series illustrated from three samples across the Givetian-Frasnian boundary within the Vorota Formation of the Kozhym River section, Sub-Polar Urals, Russia. General trends within the three ontogenetic series suggest that the ratio of basal pit width to platform width in Ancyrodella pristina, and Ancyrodella recta in creases through ontogeny but the morphology of lateral secondary keel extensions to the basal pit remains constant and is a useful taxonomic feature. Folds and collars on the basal surface occur only in the later stages of development. The out line of the platform within species is variable and controlled by the formation of incipient nodes in juveniles; gerontic specimens can also have very variable platform out lines. Measure ments of platform width to basal pit width ratios and platform shape out lines may not therefore be a good way to compare between species. The three ontogenetic series provide typical late Givetian and early Frasnian examples and increase the potential for correlation of the Middle-Upper Devonian boundary particularly using juvenile Ancyrodella specimens.
    Źródło:
    Geological Quarterly; 2007, 51, 4; 443-452
    1641-7291
    Pojawia się w:
    Geological Quarterly
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Givetian and early Frasnian cono donts from the Compte section (Middle-Upper Devonian, Spanish Central Pyrenees)
    Autorzy:
    Liao, J.-C.
    Valenzuela-Ríos, J. I.
    Powiązania:
    https://bibliotekanauki.pl/articles/2060201.pdf
    Data publikacji:
    2008
    Wydawca:
    Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
    Tematy:
    Devonian
    Spanish Pyrenees
    conodonts
    correlation
    biostratigraphy
    Opis:
    The Givetian and Frasnian conodont suc cession investigated in the Compte section (Spanish Pyrenees) is subdivided into nine Givetian standard conodont zones and two Frasnian zones (MN zones). This succession allows precise identifcation of the lower/middle Givetian, middle/upper Givetian and of the Givetian-Frasnian boundaries by means of index conodonts. The joint entry of Mesotaxis falsiovalis and Skeletognathus norrisi in the same bed shows local isochroneity of the beginning of the falsiovalis and norrisi zones in the latest Givetian. In the earliest Frasnian the sequence of Ancyrodella pristina, A. soluta and A. rotundiloba is observed whilst A. binodosa is lacking. The conodont assemblages consist of key species of the following nine genera: Polygnathus, Icriodus, Tortodus, "Ozarkodina", Schmidtognathus, Klapperina, Mesotaxis, Skeletognathus and Ancyrodella. This is the first conodont report from the Pyrenees showing such a detailed succession of enormous correlation potential.
    Źródło:
    Geological Quarterly; 2008, 52, 1; 1-1
    1641-7291
    Pojawia się w:
    Geological Quarterly
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
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