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Wyszukujesz frazę "taphonomy" wg kryterium: Temat


Tytuł:
Reassessment of the Putative Ciliate Fossils Eotintinnopsis, Wujiangella, and Yonyangella from the Neoproterozoic Doushantuo Formation in China
Autorzy:
DUNTHORN, Micah
Lipps, Jere H.
STOECK, Thorsten
Tematy:
Ciliophora, Doushantuo Formation, fossils, homology, taphonomy, diagenesis
Pokaż więcej
Wydawca:
Uniwersytet Jagielloński. Wydawnictwo Uniwersytetu Jagiellońskiego
Powiązania:
https://bibliotekanauki.pl/articles/763445.pdf  Link otwiera się w nowym oknie
Opis:
Three putative ciliate fossils were described from the Neoproterozoic Doushantuo Formation in China: Eotintinnopsis, Wujiangella, and Yonyangella. The identity of these fossils is important for our understanding of the origins and early morphological evolution within ciliate clades. Here we compare the homology of the fossil characteristics with those in their proposed ciliate relatives. Eotintinnopsis resembles a tintinnid, but its feathery tentacle-like apical structure is probably not homologous within any known ciliate. Wujiangella presents homology issues with the size and distribution of its putative somatic cilia. Yonyangella appears to be a suctorian with its tentaclelike structures, but the presence and size of its putative somatic cilia pose homology issues. We suggest that these three fossils are likely to be taphonomically and diagenetically distorted and altered acritarchs. These alterations include secondary mineral encrustations on the interiors of vesicles, the crushing, folding and other distortions of the vesicles, the bending and crushing of the acritarch spines, and the preservation of organic material in and outside of the cysts. The earliest known ciliate fossil remains a tintinnid that occurs in the Ordovician of Kazakhstan.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Coprolite of a durophagous carnivore from the Upper Cretaceous Godula Beds, Outer Western Carpathians, Poland
Autorzy:
Bajdek, P.
Tematy:
coprolite
feces content
taphonomy
turbidite sandstone
Cretaceous
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Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Powiązania:
https://bibliotekanauki.pl/articles/2059732.pdf  Link otwiera się w nowym oknie
Opis:
The Upper Cretaceous turbidite sandstones of the Godula Beds at Międzybrodzie Bialskie, Outer Western Carpathians, Poland, yielded a specimen here interpreted as a coprolite due to its elongated morphology and a high content of fragmented inoceramid shells. The coprolite was produced by a durophagous carnivore, which was most likely a teleost fish, or possibly a reptile. Coprolites are therefore confirmed to have a potential utility as aggregations of body fossils in macrofossil-poor sedimentary rocks, exemplified by the Godula Beds.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Large cruzianid trace fossils in the Ordovician of the peri-Baltic area : the case of the Bukówka Formation (Holy Cross Mountains, Poland)
Autorzy:
Stachacz, M.
Łaska, W.
Uchman, A.
Tematy:
Ordovician
trace fossils
bioturbation
Cruziana
taphonomy
Baltica
Pokaż więcej
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Powiązania:
https://bibliotekanauki.pl/articles/2059780.pdf  Link otwiera się w nowym oknie
Opis:
The Middle Ordovician Bukówka Formation, composed of fine-grained quartz sandstones with siltstone intercalations, belongs to the Kielce Region of the Holy Cross Mountains (peri-Baltic palaeogeographic position). It contains trace fossils of low diversity and poor preservation. Particularly noteworthy are the large Cruziana and Rusophycus, that are typical of peri-Gondwanan areas. They consist of casts of bilobate furrows showing diverse preservation. Other trace fossils include mostly horizontal pascichnia, cubichnia, and fodinichnia, but also vertical domichnia. The trace fossil assemblage is typical of the archetypal Cruziana and partly of the Skolithos ichnofacies. Some beds contain abundant orthid brachiopods. The trace fossils and sedimentary structures (horizontal, low-angle and wave ripple cross-laminations, hummocky cross-stratification) suggest deposition on the middle and lower shoreface with storm influence. The poor preservation and low diversity of the trace fossils are related to the homogeneous lithology, low accumulation rate, shallow burial of organic matter and strong bioturbation. Therefore, animals burrowed strongly but mostly in shallow tiers. Thus, the preservation potential of their traces was much lower than in many peri-Gondwanan sections but still higher than in Baltica sedimentary rocks. This explains the provincial differences in ichnofauna during the Ordovician, which at least partly were influenced by the preservation potential.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Life beneath ammonite shells : a unique Late Cretaceous habitat for the trace maker of Chondrites and its impact on taphonomy of the shells
Autorzy:
Uchman, Alfred
Jurkowska, Agata
Banaś, Michał
Opis:
In a unique middle Campanian horizon at Rzeżuśnia, southern Poland, the trace fossil Chondrites occurs densely and preferentially on the lower side of horizontally oriented ammonite moulds but it is absent in the surrounding sediment and on the upper side of the moulds. The ammonite shells created an ideal microenvironment for the Chondrites trace maker, with a higher organic matter content and shallower redox boundary than in the sediment outside the shells. Detailed microscopic (microfacies, SEM, CL and XRD) analyses revealed different taphonomic histories of shell for the upper and lower side of the ammonite specimens. Probably, the chemosymbiotic worm-like trace maker uses the burrow tunnels for pumping the hydrogen sulfide-rich water. This changes the pH of pore water only below the horizontally lying ammonite shells and enabled the aragonite dissolution. Slower rate of sedimentation in combination with downward migration of geochemical zones cause iron sulfide oxidation, calcite cement precipitation and glauconitization.
Dostawca treści:
Repozytorium Uniwersytetu Jagiellońskiego
Artykuł
Tytuł:
Large cruzianid trace fossils in the Ordovician of the peri-Baltic area : the case of the Bukówka Formation (Holy Cross Mountains, Poland)
Autorzy:
Stachacz, Michał
Uchman, Alfred
Łaska, Weronika
Opis:
The Middle Ordovician Bukówka Formation, composed of fine-grained quartz sandstones with siltstone intercalations, belongs to the Kielce Region of the Holy Cross Mountains (peri-Baltic palaeogeographic position). It contains trace fossils of low diversity and poor preservation. Particularly noteworthy are the large Cruziana and Rusophycus, that are typical of peri-Gondwanan areas. They consist of casts of bilobate furrows showing diverse preservation. Other trace fossils include mostly horizontal pascichnia, cubichnia, and fodinichnia, but also vertical domichnia. The trace fossil assemblage is typical of the archetypal Cruziana and partly of the Skolithos ichnofacies. Some beds contain abundant orthid brachiopods. The trace fossils and sedimentary structures (horizontal, low-angle and wave ripple cross-laminations, hummocky cross-stratification) suggest deposition on the middle and lower shoreface with storm influence. The poor preservation and low diversity of the trace fossils are related to the homogeneous lithology, low accumulation rate, shallow burial of organic matter and strong bioturbation. Therefore, animals burrowed strongly but mostly in shallow tiers. Thus, the preservation potential of their traces was much lower than in many peri-Gondwanan sections but still higher than in Baltica sedimentary rocks. This explains the provincial differences in ichnofauna during the Ordovician, which at least partly were influenced by the preservation potential.
Dostawca treści:
Repozytorium Uniwersytetu Jagiellońskiego
Artykuł
Tytuł:
Indirect biostratigraphy in condensed successions: a case history from the Bajocian of Normandy (NW France)
Autorzy:
Pavia, G.
Martire, L.
Tematy:
taphonomy
condensation
biostratigraphy
ammonites
Middle Jurassic
Normandy
Pokaż więcej
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Powiązania:
https://bibliotekanauki.pl/articles/2061355.pdf  Link otwiera się w nowym oknie
Opis:
The fossil assemblages of the Bajocian of Normandy are affected by taphonomic condensation, and the use of these assemblages for biostratigraphy must be carried out with great care because of the taphonomic reworking (reelaboration) of most of them. Nevertheless such beautiful fossils, ammonites in particular, retain their value at least as taxonomic references if their relative stratigraphic position is recognized. Such a goal has been achieved in the Bretteville section, where the "Oolithe Ferrugineuse de Bayeux" Formation (OFB), consisting of 14 beds contained within 170 cm of strata, is exposed. Each bed contains a condensed ammonite assemblage in which the overall chronologic interval represented by fossils is longer than the time of sedimentation of the bed, and no ammonites can be defined as contemporaneous with the enclosing matrix, except for the topmost two beds. The timing of biologic and sedimentary events in this Fe-oolitic succession must thus be established in an indirect way, through a stratigraphy of fossils based on their taphonomically delayed first occurrence. In particular, we can only define the maximum age of each layer, constrained by the youngest recorded fossil. On the basis of this approach, the lower part of the OFB is shown to fall within the middle to upper part of the Bajocian Stage (Humphriesianum to Parkinsoni chrons), whereas the uppermost OFB can be referred to as the uppermost Bajocian (latest Parkinsoni Chron). We conclude that, at Bretteville and in general for the Fe-oolites of Normandy, fossiliferous horizons with condensed assemblages have no value for definition of the biostratigraphic standard scale, and that indirect biostratigraphy is useful to assign minimal chronologic values to taxa when (1) their stratigraphical range has not yet been established in expanded successions, (2) they are new taxa, and (3) they are present only in a condensed succession that suffered from the same taphonomic constraints as the Bajocian of Normandy.
Dostawca treści:
Biblioteka Nauki
Artykuł

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