Preferencje help
Widoczny [Schowaj] Abstrakt
Liczba wyników

Znaleziono wyników: 17

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

help Ogranicz wyniki do:
first rewind previous Strona / 1 next fast forward last
EN
Possible plate tectonic controls on faunal diversity dynamics have been discussed in the geological literature for around 50 years. The new model of plate tectonic processes is here linked to Jurassic generic diversity (simple α-diversity) of brachiopods. This comparison offers three observations, four hypotheses and three unresolved issues. Most importantly, changes in the global plate root mean square speed coincided with brachiopod diversity dynamics, which can be explained hypothetically by either environmental disturbance triggered by more active plate motion or activity of any process (such as eustasy) tied to plate tectonic mechanisms and with an impact on marine benthic communities. It is also established that global generic diversity dynamics of brachiopods during the Jurassic coincided with the regional picture as established for the Northern Caucasus and the Swiss Jura Alps; this coincidence is difficult to explain with regard to plate tectonics. These and other speculative considerations do not clarify the role of the plate tectonic factor in Jurassic generic diversity dynamics of brachiopods, and, thus, they indicate important issues for further research.
EN
A huge isolated accumulation, more than 3 m thick and 10 m wide, of densely packed, uncrushed brachiopods has been found in Józefka Quarry within the Middle/Upper Devonian Szydłówek Beds deposited in a relatively deep environment of an intrashelf basin (Kostomłoty facies zone, western Holy Cross Mountains, Poland). The low-diversity assemblage is strongly dominated by the atrypide Desquamatia globosa jozefkae Baliński subsp. nov. and, to a lesser degree, by the rhynchonellide Coeloterorhynchus dillanus (Schmidt, 1941), which constitute 72.8% and 22.1% of the fauna, respectively. Less frequent are specimens representing the genera Hypothyridina, Schizophoria and Phlogoiderynchus. According to the conodont fauna found within the coquina bed, the stratigraphic position of the shell accumulation is close to the Givetian/ Frasnian boundary. The brachiopods are associated with numerous crinoids and less frequent bryozoans, receptaculitids (Palaeozoic problematica), sponges and solitary corals. Although it is difficult to entirely exclude the autochthonous nature of the brachiopod coquina member, its allochthonous origin and redeposition of the brachiopod shells to the deep basin by gravity flows is much more probable. Such conclusion is supported by the following facts: (1) the position of the complex in a succession of deep-marine basinal facies impoverished in oxygen; (2) its lateral thinning-out and composite internal stratification; (3) the lensshaped geometry of the coquina bed in the section perpendicular to the bedding dip; (4) high variability of the sediments preserved within the shells; and (5) the preferred orientation of the shells. The brachiopods mixed with crinoidal debris were probably transported by low-velocity, high-density, gravity-induced debris flows. Lack of fossils typical of the Middle Devonian shallows, such as massive stromatoporoids, amphiporoids and tabulates, indicates that the source area of the bioclastic material was not located in the shallowest part of the shelf, but most probably on a submarine sea-mount to the north of present-day Józefka, as suggested by earlier investigators. The triggering mechanism of the allochthonous deposition was an earthquake rather than storm activity. The enormous thickness of the brachiopod complex is probably caused by the sinking of bioclastic material, transported in succeeding depositional multi-events, in a soft, muddy bottom, typical of the Szydłówek Beds deposition.
EN
Small brachiopods of the families Craniidae Menke, 1828 and Thecidellinidae Elliott, 1958 were selected from the Oxfordian sequence which lies transgressively upon a Variscan rhyodacite laccolite exposed at Zalas in the Cracow Upland, southern Poland, a site which is well-known due to various kinds of ubiquitous fossils. The craniids include three species: Craniscus bipartitus (Münster in Goldfuss, 1837), Craniscus tripartitus (Münster in Goldfuss, 1837) and Craniscus antiquior (Jelly, 1843), and the thecidellinids – two species: Rioultina zalasensis sp. nov. and Rioultina wapiennensis Krawczyński, 2008. The species described herein indicate tropical or subtropical waters, and a moderately (?) deep character of the sea basin at Zalas.
EN
Detailed biogeographical and biofacies analyses of the Late Ordovician brachiopod faunas with 160 genera, grouped into 94 faunas from individual lithotectonic units within the Kazakh Orogen strongly support an archipelago model for that time in that area. The Kazakh island arcs and microcontinents within several separate clusters were located in the tropics on both sides of the Equator. Key units, from which the Late Ordovician faunas are now well known, include the Boshchekul, Chingiz-Tarbagatai, and Chu-Ili terranes. The development of brachiopod biogeography within the nearly ten million year time span of the Late Ordovician from about 458 to 443 Ma (Sandbian, Katian, and Hirnantian), is supported by much new data, including our revised identifications from the Kazakh Orogen and elsewhere. The Kazakh archipelago was west of the Australasian segment of the Gondwana Supercontinent, and relatively near the Tarim, South China and North China continents, apart from the Atashu-Zhamshi Microcontinent, which probably occupied a relatively isolated position on the south-western margin of the archipelago. Distinct faunal signatures indicate that the Kazakh terranes were far away from Baltica and Siberia throughout the Ordovician. Although some earlier terranes had joined each other before the Middle Ordovician, the amalgamation of Kazakh terranes into the single continent of Kazakhstania by the end of the Ordovician is very unlikely. The Late Ordovician brachiopods from the other continents are also compared with the Kazakh faunas and global provincialisation statistically determined.
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 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.
EN
The Ordovician sedimentary succession of the Pol-e Khavand area, situated on the northern margin of the Yazd block, has important differences from those in other parts of Central Iran. It has been established that the presumably terminal Cambrian to Lower Ordovician volcano-sedimentary Polekhavand Formation, exposed in the Pol-e Khavand area, has non-conformable contact with greenschists of the Doshakh Metamorphic Complex. The succeeding, mainly siliciclastic Chahgonbad Formation contains low to moderately diverse faunal assemblages, including brachiopods, cephalopods, trilobites and tentaculitids. The Darriwilian age of the lower part of the formation is well established by the co-occurrence of brachiopod genera Camerella, Phragmorthis, Tritoechia and Yangtzeella. The associated rich cephalopod fauna is different from the Darriwilian cephalopod associations of the Alborz terrane and may show some affinity with warm water faunas of North China and South Korea. It is likely that the Mid Ordovician fauna recovered from the lower part of the Chahgonbad Formation settled in the area sometime during a warming episode in the late Darriwilian. By contrast the low diversity mid Katian brachiopod association includes only three taxa, which occur together with the trilobite Vietnamia cf. teichmulleri and abundant, but poorly preserved tentaculitids questionably assigned to the genus Costatulites. This faunal association bears clear signatures linking it to the contemporaneous cold water faunas of the Arabian, Mediterranean and North African segments of Gondwana. Four brachiopod species recovered from the Chahgonbad Formation, including Hibernodonta lakhensis, Hindella prima, Lomatorthis? multilamellosa and Yangtzeella chupananica are new to science.
EN
At a glance, progress in palaeontology and eustatic reconstructions in the past decade permits to prove or to disprove the possible dependence of Palaeozoic brachiopod generic diversity dynamics on global sea-level changes. However, the available diversity curve is of much lower resolution than the eustatic curve. This problem can be resolved by decreasing the resolution of the latter. The other restriction linked to the chronostratigraphical incompatibility of the available data allows to focus on the Middle Palaeozoic only. A series of mass extinctions and other biotic crises in the Silurian-Devonian does not allow to interpret correctly the results of direct comparison of the brachiopod generic diversity dynamics with global sea-level changes. With the available data, it is only possible to hypothesize that the eustatic control was not playing a major part in diversity dynamics of Middle Palaeozoic brachiopods. The resolution of the stratigraphic ranges of Palaeozoic brachiopods should be increased significantly, and these ranges should be plotted against the most up-to-date geologic time scale. Until this task will be achieved, it is impossible to judge about the existence of any dependence (either full or partial) of the Palaeozoic brachiopod diversity dynamics on global sea-level changes.
EN
A new species of micromorphic articulate brachiopod (Rhynchonellida) Lambdarina jugowiensis sp. nov., from the upper Viséan (Sokolec Beds) of central Sudetes, SW Poland, is described. The studied specimens are calcified, what makes them unique in respect of their state of preservation. The material is represented by a full range of growth stages; from brephic to gerontic. Based on its morphological features and the palaeogeographical distribution of all its known species, two main evolutionary lines are proposed for the genus; the Australian and the European ones. Lambdarina was widely distributed in the equatorial-tropical waters of marginal seas of the Palaeotethys Ocean, mostly during Mississippian time.
EN
The Matmor Formation is a set of late Callovian marls and limestones exposed in the Matmor Hills, Hamakhtesh Hagadol, southern Israel. It was deposited during a regional transgression which produced patch reefs across a shallow carbonate platform in this area. The thecideide brachiopods described here were part of a diverse sclerozoan community which encrusted the calcareous surfaces of sponges and corals. These brachiopods represent a new, very small species of Moorellina and the only thecideide brachiopod found in the Jurassic deposits of the Middle East. A gall-like structure interpreted as the trace of the parasitic (ascothoracid?) infestation has been recorded in one specimen of Moorellina negevensis sp. nov.
EN
New biostratigraphic and lithostratigraphic data are presented for the tectonically reduced Ordovician succession at Pobroszyn in the Łysogóry region of the Holy Cross Mountains, central Poland. Only some of the chronostratigraphic units known from the Łysogóry region can be recognized in this section. However, based on lingulate brachiopods, conodonts, acritarchs and chitinozoa, the units present may be referred to the Late Tremadoc, Late Arenig, Early Lanvirn, Late Lanvirn, Early Caradoc and to the Middle Caradoc and Ashgill. New lithostratigraphic units are established in the lower part of the Ordovician of the Pobroszyn section: the Opatówka Mudstone/Sandstone Formation (?Late Tremadoc) and the Pobroszyn Sandstone Formation (Late Arenig). Three species of lingulate brachiopods are described, of which two are new: Myotreta anitae and Eoconulus lilianae. The conodonts and acritarchs are illustrated and briefly discussed.
12
Content available remote The Upper Oxfordian (Jurassic) thecideide brachiopods from the Kujawy area, Poland
EN
Thecideide brachiopods from the slope facies of a sponge-cyanobacterial bioherm exposed in the Wapienno and Bielawy quarries (Kujawy, Poland) are described. Numerous specimens were found in the upper part of the section, in the Hauffianum-Planula Subzones of the Oxfordian, and constitute the first record of these brachiopods from the Jurassic deposits in the area. Two species: Rioultina wapiennensis sp.nov. and Neothecidella ulmensis QUENSTEDT, 1858, are described, the first being the only representative of the genus Rioultina found in Poland. Excellent preservation of some specimens enabled recognition of details of their internal morphology usually inaccessible in fossil material, including features associated with reproduction and the development of the brachidium. Study of relatively large numbers of thecideides still cemented to the substrate, together with analysis of the associated fauna, allowed the reconstruction of aspects of their ecology.
13
Content available remote The Devonian of Western Karakorum (Pakistan)
EN
Devonian rocks crop out in several thrust sheets in the sedimentary belt of North-Western Karakorum, both to the south and to the north of the Reshun Fault. Gently metamorphosed Devonian dolostones and volcanics are also present in the Tash Kupruk Zone north of the thrust sheet system. The most complete succession is found in the Karambar Thrust sheet where dolostones and recrystallized limestones (Vandanil Formation) lie above the black shales and siltstones of the Baroghil Group. The age of the Vandanil Formation is poorly defined, approximating latest Silurian or earliest Devonian at its base and proven to be Pragian in the 4th of its 5 lithozones. The overlying Chilmarabad Formation is divided into two members. The lower member is a mixed siliciclastic-carbonate package, present in most southern and western thrust sheets. The upper member is ubiquitous; it consists of dolostones, often stromatolitic. The calcareous part of the Tash Kupruk Zone consists of similar facies. The carbonate flats of the Chilmarabad Formation display a trend towards emersion towards the top, and are overlain, with regional unconformity, by the basal unit of the Shogram Formation. The base of the latter consists of arenite and fine conglomerate (deposited in an alluvial setting) overlain by alternating marine bioclastic limestones and litharenites with one or two coral bafflestones in the middle to upper part. The age of the lowermost part of the Shogram Formation is Givetian, extending through the Frasnian and seemingly into the Famennian, but the last is poorly documented (contrasting with the classic Shogram and Kuragh sections of Chitral); it reflects a return to fine terrigenous input. The inferred palaeogeography accords with the Northern Karakorum having been part of the Gondwana margin during the Devonian. Awide, mostly calcareous platform, characterised extensive areas of the Karakorum, Central Pamir, Badakhshan and, in a minor way, Central Afghanistan (Helmand Block). The sandstone petrography suggests that clastics polluting the carbonates originated from erosion of a pre-existing sedimentary cover. During the Givetian a first rifting episode, possibly echoing the opening of an ocean to the east, affected the whole area,with volcanic outpourings in the rifts, while eroding shoulders fed the basins, though never extending as deep as the crystalline basement. A minor volcanic input is also recorded. The tectonic pulse almost ceased during the Frasnian, gradually resuming towards the end of the Devonian.
EN
A survey of the principal benthic faunas from the Devonian of the Ardennes is presented. The [alfa] diversity is very high (707 species, including 138 species of stromatoporoids, 113 species of tabulates, hydroids and chaetetids, and 456 species of brachiopods). Analysis of their distribution through time indicates two brachiopod diversity peaks (Emsian/Eifelian and Frasnian), a single stromatoporoid diversity peak (Givetian), and no clear peak of tabulate corals (with the highest diversification during the Eifelian.Frasnian). The highest diversity of bioconstructors in the Givetian correlates with a decrease in brachiopod diversity. Changes in the vertical distribution of the faunas are correlated with the facies development: the development of carbonates correlates with the abundance of stromatoporoids and tabulates, while brachiopods were most abundant before and after the peak of carbonate development. Bioconstructors are absent (or nearly absent) in siliciclastic facies.
EN
The presented paper contains a detailed description of four species of the genus Craniscus DalI, 1871, found in the Upper Oxfordian of Bielawy and Wapienno quarries, Kujawy area. Three of them: Craniscus bipartitus (Munster, 1837), Craniscus antiquior (Jelly, 1843) and Craniscus corallinus (Quenstedt, 1852) have already been described from Poland, the fourth, however - Craniscus tripartitus (Munster, 1840), had only been known from the Lower Oxfordian of North Bavaria. The Craniscus specimens come from slope deposits of sponge-microbialitic bioherm. This is indicated by the fact that almost all specimens are dorsal valves, separated posthumously from ventral valves. The condition of some specimens and the rock lithology suggests, that the deposition was very violent in some cases and brachiopods were buried alive. The studied material is relatively well-preserved, which alIowes an accurate reading of the location of muscle scal's.
17
Content available remote Lower Devonian Lingulata from the well Ursynów 1 (E Poland)
EN
New data are presented for the poorly known Devonian lingulate fauna. Late Lochkovian members of the lingulate genera: ?Lingularia, 'Trigonoglossa', Lingulodiscina, Orbiculoidea and Schizotreta are described. The material is from a depth 2858.1-2979.1 m of the well Ursynów 1, situated in the NW part of the Radom-Lublin area (E Poland), together with a simplified lithological section of the Lower Devonian
PL
Podano opisy kilku przedstawicieli rodzajów ?Langularia, 'Trigonoglossa', Lingulodiscina, Orbiculoidea oraz Schizotreta. Materiał pochodził z otworu wiertniczego Ursynów 1 z głębokości 2858,1-2979,1 m, usytuowanego w NW części obszaru radomsko-lubelskiego (E Polska). Podano także skondensowany opis profilu litologicznego odwierconych osadów dewonu, a opisana fauna wskazuje na późnolochkowski wiek.
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.