Preferencje help
Widoczny [Schowaj] Abstrakt
Liczba wyników
Powiadomienia systemowe
  • Sesja wygasła!

Znaleziono wyników: 14

Liczba wyników na stronie
first rewind previous Strona / 1 next fast forward last
Wyniki wyszukiwania
Wyszukiwano:
w słowach kluczowych:  mastrycht
help Sortuj według:

help Ogranicz wyniki do:
first rewind previous Strona / 1 next fast forward last
EN
Biostratigraphic analysis of calcareous nannofossils from the Pełczyska section in the Miechów Trough (southern Poland) has revealed that the entire section covers the lowermost Maastrichtian. The UC16bTP Tethyan subzone is designated based on the presence of Broinsonia parca constricta Hattner, Wind and Wise, 1980, reworked remains of Uniplanarius trifidus (Stradner) Hattner and Wise in Wind and Wise, 1983 and the simultaneous lack of Eiffellithus eximius (Stover) Perch-Nielsen, 1968. The studied section spans also the interval between the LO of Zeugrhabdotus praesigmoides Burnett, 1997 and the FO of Prediscosphaera mgayae Lees, 2007 (UC16 S3 Boreal subzone). Quantitative analysis of nannofossil assemblages has shown the dominance of cold water species (up to 50%), e.g., Micula decussata Vekshina, 1959, Prediscosphaera spp., Arkhangelskiella spp., Calculites obscurus (Deflandre) Prins and Sissingh in Sissingh, 1977 and Lucianorhabdus cayeuxii Deflandre, 1959. In the early Maastrichtian, the studied area was more influenced by cool water masses from the Boreal Province rather than by warm water from the Tethyan Province. The significant predominance of cold water taxa and the elevated presence of Prediscosphaera cretacea (Arkhangelsky) Gartner, 1968 also supports the hypothesis of climate cooling in the early Maastrichtian.
EN
The Maastrichtian sediments of northern Iraq are rich in larger benthic foraminifera. Among them, the genus Loftusia is well-known one because of its significant palaeogeographic distribution across the Mediterranean and Middle East. In this study, observations of abnormal test shapes, species recognition criteria and endoskeleton characteristics of Loftusia are discussed, based on the new material from north-eastern Iraq. The following species of Loftusia are described: Loftusia elongata Cox, L. persica Brady, Loftusia morgani Douvillé, L. anatolica Meriç, L. matsumarui Meriç and Görmüs, L. minor B Cox, L. ketini B Meriç and L. kahtaensis Meriç, Loftusia minor A Cox, L. oktayi Meriç and L. baykali Meriç. The predominant species are Loftusia elongata, L. morgani and L. baykali. Skewed abnormal individuals and epidermal parts of the endoskeleton structure are also interesting aspects to note. Quantitative data obtained for Loftusia allow us to better understand and interpret species identification criteria, abnormal occurrences and the endoskeleton structure.
EN
A new cephalopod collection from the Campanian-Maastrichtian boundary interval of NE Mexico, consisting of 1076 individuals assigned to 29 species and 22 genera is presented. This collection is a mix of ammonoids, one coleoid and one nautilid, which originate from at least three ammonoid biozones: The upper Campanian Exiteloceras jenneyi and Nostoceras (Nostoceras) hyatti zones, and the lower Maastrichtian Pachydiscus (Pachydiscus) neubergicus Zone. The age of the collection is thus middle late Campanian to late early Maastrichtian, and it closes a stratigraphic gap between faunas described formerly from this region. The specimens are nuclei collected from the desert pavement. The abundance of specimens allows for a comparison to other Campanian-Maastrichtian ammonoid records from Mexico, North America and Europe.
EN
The benthic macroinvertebrates of the Lower Maastrichtian chalk of Saturn quarry at Kronsmoor (northern Germany)been studied taxonomically based on more than 1,000 specimens. Two successive benthic macrofossil assemblages were recognised: the lower interval in the upper part of the Kronsmoor Formation (Belemnella obtusa Zone) is characterized by low abundances of macroinvertebrates while the upper interval in the uppermost Kronsmoor and lowermost Hemmoor formations (lower to middle Belemnella sumensis Zone) shows a high macroinvertebrate abundance (eight times more than in the B. obtusa Zone) and a conspicuous dominance of brachiopods. The palaeoecological analysis of these two assemblages indicates the presence of eight different guilds, of which epifaunal suspension feeders (fixo-sessile and libero-sessile guilds), comprising approximately half of the trophic nucleus of the lower interval, increased to a dominant 86% in the upper interval, including a considerable proportion of rhynchonelliform brachiopods. It is tempting to relate this shift from the lower to the upper interval to an increase in nutrient supply and/or a shallowing of the depositional environment but further data including geochemical proxies are needed to fully understand the macrofossil distribution patterns in the Lower Maastrichtian of Kronsmoor.
EN
The inarticulate brachiopod Discinisca is a rare faunal element in the Upper Cretaceous of the U.S. Western Interior. We report two occurrences of encrustation of Discinisca on a scaphitid ammonite (scaphite) and several inoceramids from the lower Maastrichtian Baculites baculus/Endocostea typica Biozones of the Pierre Shale at two localities. Six specimens of Discinisca are present on a single specimen of Hoploscaphites crassus from eastcentral Montana. They occur along the furrow at the mature apertural margin. Because the brachiopods are restricted to the margin and do not occur on the rest of the shell, it is likely that they encrusted the ammonite during its lifetime. If so, this implies that the soft body of the scaphite did not cover the outside surface of the aperture, leaving this area vulnerable to epizoan attachment. A total of 13 specimens of Discinisca are also present on four specimens of Cataceramus? barabini from east-central Wyoming. The brachiopods occur in crevices on the outside of the shells and may have encrusted the inoceramids after their death as the shells began to break down and delaminate, resulting from the decomposition of the organic matrix holding them together. Based on the faunal assemblages at both localities, the presence of Discinisca may indicate environments with either low oxygen levels and/or few predators or competitors.
EN
The taxonomy and stratigraphy of the Upper Campanian and Lower Maastrichtian belemnites from the Vistula (central Poland) and Kronsmoor (northern Germany) sections are revised on the basis of new collections from the Vistula section as well as a reinvestigation of the classic collection of Schulz from the Kronsmoor section. For the taxonomic description a new biometric procedure is proposed, which can be applied to both the genera Belemnella and Belemnitella. For the species-level taxa recognition the Artificial Neural Networks method, the self-organizing Kohonen algorithm, was implemented. This new taxonomic and methodological approach enabled the recognition of nine species of the genus Belemnella. Five of them can be assigned to the existing species B. lanceolata, B. longissima, B. inflata, B. obtusa and B. vistulensis. However, the species concept differs from that applied by Schulz (1979). As a consequence, the stratigraphic ranges of these species are modified. Four species are left in open nomenclature and represent possibly new species. Future studies may reveal that they might be assigned to East European forms from Ukraine or Russia. The species of Belemnella recognized are placed into the stratigraphic framework based on the standard ammonite and inoceramid bivalve zonations, especially those recognized in the Vistula section. The newly proposed belemnite zonation for the Vistula and Kronsmoor sections is correlated via inoceramids with the standard GSSP at Tercis, France, in order to identify the base of the Maastrichtian Stage. The Campanian/Maastrichtian boundary as defined in Tercis is placed here at the base of the newly defined B. obtusa and B. vistulensis Zones ["obtusa/vistulensis"] - thus it is markedly higher than the traditional boundary based on the FAD of representatives of the genus Belemnella - This new boundary coincides well with a distinct turnover of belemnite guard morphology and represents one of the most important points in the early evolutionary history of Belemnella. Three belemnite zones defined by their lower boundaries are recognized in the Campanian/Maastrichtian interval, in addition to three subzones recognized within the B. obtusa Superzone. The B. lanceolata and B. inflata zones as understood here are referred to the Upper Campanian [Tercis definition]. The B. obtusa Zone is subdivided into three subzones, viz.: Belemenlla vistulensis, Belemnella sp. G and Belemnella sp. F, which are referred to the Lower Maastrichtian [Tercis definition]. The fast evolving species of Belemnella enable the proposal of a biostratigraphic scheme with a resolution that is higher than those based on inoceramid bivalves and ammonites - the longevity of a belemnite zone could be as low as 200Ky.
EN
The formal definition of the Global Stratotype Section and Point (GSSP) for the base of the Maastrichtian Stage at Tercis, southwest France, is based on the first or last occurrences of twelve taxa, including three species of ammonites, Pachydiscus (Pachydiscus) neubergicus, Diplomoceras cylindraceum, and Nostoceras (Nostoceras) hyatti. The taxonomy and stratigraphical distribution of these, and allied forms, are studied, on the basis of material from the opoka succession across the upper Campanian.lowermost Maastrichtian boundary in the Middle Vistula River section, central Poland. in view of the imprecise location of two ammonite GSSP markers in that section, a direct ammonite-based correlation with the GSSP at Tercis is impossible. however, data available indicate that in the Middle Vistula River section the first occurrence of Pachydiscus (P.) neubergicus and the last occurrence of Nostoceras (N.) hyatti are situated significantly higher than the first occurrence of Belemnella lanceolata, the traditional belemnite marker for the base of the Maastrichtian Stage in the Boreal Realm, and that Diplomoceras cylindraceum appears significantly below this level. There are no unequivocal records of Pachydiscus (P.) neubergicus from the Belemnella lanceolata Zone s.l. in the Middle Vistula River section.
EN
The Campanian-Maastrichtian boundary interval of the Middle Vistula River valley section (central Poland) represents a continuous, lithologically monotonous, fossiliferous succession, with a good stable isotope and palaeomagnetic signal. It yields all the biostratigraphically critical macro- and microfossil groups: ammonites, belemnites, inoceramid bivalves, foraminifera, nannofossils and dinoflagellates. Additionally, it is located in the transitional zone between the Boreal and Tethyan biogeographic provinces, as well as between the western and eastern biogeographic areas of Europe. The section supplements the data on the interval acquired recently from the basal Maastrichtian stratotypic section in Tercis, south-west France, and from the interval reference section in Kronsmoor, northern Germany.
EN
The sponge fauna from the Upper Campanian.lowermost Maastrichtian succession of the Middle Vistula River valley (central Poland) is represented mainly by dictyid hexactinellid sponges (Hexactinosida and Lychniscosida). Their greatest abundance and taxonomic variability is noted in the "Inoceramus" inkermanensis Zone (Upper Campanian), and they are less diverse in the overlying (Upper Campanian) Trochoceramus costaecus Zone and lower "Inoceramus" redbirdensis Zone. In the upper "Inoceramus" redbirdensis Zone (basal Maastrichtian in the sense of the Tercis rather than the Boreal definition) they are extremely rare. With the beginning of the Maastrichtian the number of dictyid sponges gradually increases. The observed changes in the abundance and taxonomic variability of the dictyid sponges indicate environmental changes in the latest Campanian.earliest Maastrichtian sea in the area. It seems that changes in basin bathymetry, confined to eustatic sea-level changes in the latest Campanian and early Maastrichtian, were the most important factor. Progressive shallowing of the basin in the latest Campanian drastically restricted the development of dictyids. In the peak regression, the sea level could have fallen to only several tens of metres. The gradual recovery of the sponge assemblages correlates with subsequent deepening of the basin with the start of the Maastrichtian.
EN
Representatives of the belemnite genus Belemnella from the uppermost Campanian and lowermost Maastrichtian of the Middle Vistula River Valley section (central Poland) have been studied, using the species concept proposed by Schulz in 1979. Results have been compared to a recently proposed new interpretation of the genus Belemnella based on artificial neural networks, as put forward by Remin in 2007 and 2012. In the interval studied, four taxa have been recognised: Bln. longissima, Bln. inflata, Bln. obtusa and Bln. vistulensis, the last-named being a senior synonym of Bln. pseudobtusa. Three additional forms have been left in open nomenclature: Bln. cf. lanceolata, Bln. ex gr. lanceolata/inflata and Belemnella sp. Based on their documented vertical ranges, three Belemnella standard zones, as originally distinguished in the Kronsmoor section by Schulz (1979), northern Germany, have been defined, in ascending order: the Bln. lanceolata, Bln. vistulensis and Bln. obtusa zones. The bases of the lanceolata and obtusa zones in the Middle Vistula River Valley section can be directly correlated with the same zones at Kronsmoor, and appear to be isochronous within limits of stratigraphic resolution. The base of the vistulensis Zone (Bln. vistulensis according to the species concept of Schulz in 1979), however, is probably diachronous, being older in the Middle Vistula section. Although Schulz's and Remin's species concepts differ quite considerably, they do result in similar stratigraphic subdivisions of the Kronsmoor and Middle Vistula River sections.
EN
Results of detailed multistratigraphic analyses of the Campanian.Maastrichtian boundary section at Kronsmoor in northern Germany are summarised and calibrated with the GSSP at Tercis les Bains, southwest France. Additional markers for the definition of the boundary in the Boreal Realm are proposed, and a detailed carbon isotope curve around the Campanian.Maastrichtian boundary in the chalk facies of the Boreal epicontinental sea is presented. The C isotopic GSSP marker for global correlation is the markedly abrupt decrease of c. 0.7 [per mil] [delta^13]C directly at the Campanian.Maastrichtian boundary as dated by ammonites. In electronic borehole measurements the Kronsmoor section covers the SP peaks 53 to 64 and the base of the Maastrichtian being situated just below SP peak 60. The first occurrence (FO) of the ammonite Pachydiscus neubergicus, which corresponds to biohorizon 1 at Tercis, falls in the upper part of nannofossil Zone UC15, at both localities. Biohorizon 3 is the FO of the ammonite Diplomoceras cylindraceum, which first appears in the Upper Campanian of Tercis and at Kronsmoor enters significantly above the FO of Belemnella lanceolata, the conventional Boreal belemnite marker for the base of the Maastrichtian Stage. Based on ammonite evidence, the internationally accepted base of the Maastrichtian at Kronsmoor is located between the FOs of Diplomoceras cylindraceum (Upper Campanian) and Pachydiscus neubergicus (Lower Maastrichtian) c. 11 m above flint layer F 600, at which the first representatives of the belemnite genus Belemnella, in particular Bn. lanceolata occur. The latter thus is a Late Campanian species, appearing c. 450 ky prior to the ammonite-based boundary. The FOs of Belemnella pseudobtusa (sensu Schulz) resp. Belemnella obtusa (sensu Remin) directly at the boundary can be use as the coleoid proxy for the definition of the base of the Maastrichtian in the Boreal Realm. To define the boundary by benthic foraminifera the last occurrence (LO) of Neoflabellina praereticulata is suitable. Biohorizon 12, as defined at Tercis, involves the nannofossil Uniplanarius trifidus, however, at Kronsmoor this species is rare, occurs only sporadically and also significantly lower in comparison to Tercis. It is possible though to compare and correlate nannofossil events between Kronsmoor and Tercis using cosmopolitan taxa such as Broinsonia parca constricta and Eiffellithus eximius. The LO of the latter appears to be situated just above the boundary in both sections; it follows from this that the top of nannofossil Zone UC15 is of Early Maastrichtian age.
EN
The phymosomatid Trochalosoma taeniatum (von Hagenow, 1840) is recorded for the first time from upper Maastrichtian strata exposed at Piotrowice, near Lublin, southeast Poland. Although fragmentary, the single, moderately preserved test is of note in representing one of the larger individuals of this species on record (estimated diameter > 60 mm), and in displaying crenulate ambulacral and interambulacral tubercles, at least adapically. Previous records of T. taeniatum include the lower and upper Maastrichtian of Denmark, northern Germany (Rugen), Alava (northern Spain) and Mangyshlak (Kazakhstan). Trochalosoma corneti (Cotteau, 1875), from the upper Maastrichtian of southern and northeast Belgium (Mons and Liege basins, respectively) and the southeast Netherlands (type area of the Maastrichtian Stage), synonymised by some authors with T. taeniatum, is considered to be distinct.
EN
Based on high resolution biostratigraphic analysis of planktic foraminifers, it is confirmed that the Bidart section (eastern margin of the Atlantic Ocean) represents a continuous Cretaceous-Paleogene (K-Pg) succession. Nevertheless, the foraminiferal species Plummerita hantkeninoides, regarded as a latest Maastrichtian marker species, is absent and Abathomphalus mayaroensis ranges to the top of the Maastrichtian (= K/Pg boundary). Pseudoguembelina hariaensis is present throughout the succession, and it is proposed herein to substitute Pl. hantkeninoides as the marker of the uppermost Maastrichtian. At least 53 out of 72 species became suddenly extinct at the K/Pg boundary, defined by the Ir anomaly (Bonte et al. 1984; Delacotte et al. 1982). The extinct species are represented by globotruncanids and large heterohelicids, characteristic of the tropical-subtropical deep photic sea water under the mesotrophic conditions of the Late Maastrichtian. The Lower Danian succession (the zones of Guembelitria cretacea, Parvularugoglobigerina eugubina, Parasubbotina pseudobulloides) is less expanded than at El Kef (Tunisia) [the Global Stratotype Section and Point (GSSP) for the Cretaceous/Paleogene (K/Pg) boundary] or at Elles (Tunisia) [its auxiliary section].
PL
W pelagicznych osadach jednostki podśląskiej (marglach węglowieckich, marglach typu frydeckiego, marglach żegocińskich, piaskowcach z Rybia) oraz w marglach bakulitowych jednostki skolskiej i marglach z Bonarki występujących na monoklinie śląsko-krakowskiej (odsłonięcie Bonarka w Krakowie) stwierdzono liczne formy nanoplanktonu wapiennego wieku kampan-mastrycht. Wyznaczono poziomy nanoplanktonowe, określając wiek badanych osadów. W marglach bakulitowych, nazywanych też marglami z Węgierki, występujących w jednostce skolskiej, odnotowano podobny skład i charakter nanoplanktonu wapiennego jak w szarych marglach typu frydeckiego występujących w jednostce podśląskiej w zachodniej części Karpat. W badanych osadach jednostki podśląskiej nie stwierdzono ciągłego przejścia sedymentacyjnego między osadami mastrychtu i danu. Badania nanoplanktonu potwierdziły istnienie połączenia między strefą borealną i tetydzką na obszarze polskich Karpat zewnętrznych w kampanie i mastrychcie, o czym świadczy obecność w próbkach form nanoplanktonu uważanych za typowo borealne.
EN
In pelagic sediments of the Subsilesian Unit (Węglówka marls, Frydek-type marls, Żegocina marls and Rybie sandstones) and in the bakulit marls from the Skole Unit, and in marls from Bonarka in Silesian-Cracow Monocline many forms of calcareous nannoplankton of Campanian-Maastrichtian age were noted. Distinguishing of several nannoplankton assemblage zones allowed for more detailed time resolution of the studied sediments. Existing of the connection between the boreal and Tethyan realms in Polish Outher Carpathians during Campanian/Maastrichtian has been confirmed. Calcareous nannoplankton of the bakulit marls (Skole Unit) appeared similar to that from the Frydek-type marls (Subsilesian Unit). No continuous transition between sediments of the Maastrichtian and Danian within the studied Subsilesian Unit has been stated. Transition between Boreal and Tethyan realms on the Polish Outher Carpathians area, during Campanian and Maastrichtian age are confirmed.
first rewind previous Strona / 1 next fast forward last
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.