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Wyszukujesz frazę "Gondwana." wg kryterium: Wszystkie pola


Wyświetlanie 1-4 z 4
Tytuł:
Large tridactyl dinosaur tracks from the Early Jurassic of southern Gondwana : uppermost Elliot Formation, Upper Moyeni, Lesotho
Autorzy:
Abrahams, Miengah
Sciscio, Lara
Reid, Mhairi
Haupt, T’nielle
Bordy, Emese M.
Powiązania:
https://bibliotekanauki.pl/articles/1836362.pdf
Data publikacji:
2020
Wydawca:
Polskie Towarzystwo Geologiczne
Tematy:
vertebrate ichnology
tridactyl
large theropods
southern Gondwana
Karoo
upper Elliot Formation
Opis:
A new ichnosite in southwest Lesotho (Upper Moyeni; Quthing District) is located within the uppermost part of the highly fossiliferous Elliot Formation, ~35 m below the conformably overlying Clarens Formation and ~65 m above the world-renowned Lower Moyeni ichnosite. While the Lower Moyeni site preserves diverse Early Jurassic ichnofossils, the ichnites at the Upper Moyeni comprise one vertebrate burrow and ~50 tridactyl tracks with footprint lengths between 15 and 51 cm. Many of the tracks preserve digital pad impressions, claw marks and displacement rims, all related to substrate conditions. The morphometric parameters of the Upper Moyeni tracks are consistent with Grallator, Eubrontes and Kayentapus. Several larger tracks with footprint lengths > 40 cm are Kayentapus-like and Eubrontes-like, and are comparable to previously described very large theropods tracks with lengths > 50 cm from the uppermost Elliot and Clarens formations. On the basis of sedimentological and ichnological evidence, the Upper Moyeni ichnofossils were formed in a palaeolandscape with small rivers and shallow lakes by burrowing tetrapods and a variety of bipedal dinosaurs (theropods), some of which were up to 7–8 m in body length. The Upper Moyeni tracks, together with the other very large tracks from coeval locations in southern Africa, collectively highlight the tendency towards increasing diversity in size of tridactyl tracks and by extension theropod trackmaker body size body size, which runs in tandem with the increasing diversity of non-sauropod, sauropodomorph body fossils in the Sinemurian-Pliensbachian of southern Gondwana.
Źródło:
Annales Societatis Geologorum Poloniae; 2020, 90, 1; 1-26
0208-9068
Pojawia się w:
Annales Societatis Geologorum Poloniae
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Rare-earth and trace elements of the lower Cambrian–Lower Cretaceous siliciclastic succession of NE Gondwana in Jordan : from provenance to metasomatism
Autorzy:
Amireh, Belal S.
Saffarini, Ghazi A.
Amaireh, Mazen N.
Jarrar, Chaleb H.
Abed, Abdulkader A.
Powiązania:
https://bibliotekanauki.pl/articles/2134835.pdf
Data publikacji:
2022
Wydawca:
Polskie Towarzystwo Geologiczne
Tematy:
Jordan
NE Gondwana
rare-earth and trace elements
fractionation
provenance proxies
Arabian-Nubian Shield
siliciclastics
Opis:
The present bulk-rock geochemical study aims to answer some questions concerning the distribution and variability of trace elements (TEs) and rare earth elements (REEs) in the lower Cambrian–Lower Cretaceous sandstones and mudstones of NE Gondwana in Jordan. The study proved that the REE and the TE distribution patterns in both detrital and authigenic, light and heavy minerals are controlled principally by the source-rock provenance, followed by an interplay of many factors: chemical weathering, recycling, hydraulic sorting, locally low-temperature, hydrothermal metasomatism, depositional environment and redox conditions, and diagenesis. On the basis of specific trace elements, trace-element ratios, and petrographic proxies, the provenance is constrained to be mainly felsic-, rarely mafic granitoids of the Arabian-Nubian Shield, and less commonly, recycled Palaeozoic and Mesozoic siliciclastic strata. REEs are hosted mainly in zircon, Ti-bearing minerals, and partly in clay minerals. They were depleted by both chemical weathering and recycling; nevertheless, they were enriched by subsequent hydraulic sorting and low-temperature, hydrothermal metasomatism. Chemical weathering initially depleted zirconium. However, this was counteracted by subsequent enrichment through recycling, hydraulic sorting, and low-temperature, hydrothermal metasomatism. The fractionation of the other TEs, due to these sedimentological factors during the genesis of subarkosic arenites, quartz arenites and mudstones, is discussed and some conclusions are derived. The Eu negative anomaly was enhanced significantly by recycling and low-temperature, hydrothermal metasomatism. Scandium abundance increased with decreasing grain size from coarse sand to the mud fraction. The recorded REE and TE fractionation might also apply to siliciclastics in similar, geological environments.
Źródło:
Annales Societatis Geologorum Poloniae; 2022, 92, 2; 109--158
0208-9068
Pojawia się w:
Annales Societatis Geologorum Poloniae
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Dinosaur behaviour in an Early Jurassic palaeoecosystem – uppermost Elliot Formation, Ha Nohana, Lesotho
Autorzy:
Rampersadh, A.
Bordy, E. M.
Sciscio, L.
Abrahams, M.
Powiązania:
https://bibliotekanauki.pl/articles/191599.pdf
Data publikacji:
2018
Wydawca:
Polskie Towarzystwo Geologiczne
Tematy:
vertebrate ichnology
tridactyl
tetradactyl
climate change
southern Gondwana
Karoo
upper
Elliot Formation
Opis:
The Ha Nohana palaeosurface in southern Lesotho preserves tridactyl and tetradactyl tracks and trackways attributable to Early Jurassic bipedal, theropod-like dinosaurs. Complementary sedimentological and ichnological observations along the palaeosurface and in the strata below and above it allow detailed interpretations of climatically driven changes in this southern Gondwana palaeoecosystem. Sedimentological evidence suggests trackmaking under a semi-arid climate with heavy storms and episodic flash flooding that induced ephemeral, unconfined sheetwashes. The palaeosurface is overlain by rhythmically bedded, organic-matter rich mudstones that formed in a deep, stratified lake indicative of a longer and wetter period in the history of the site. The unique morphological details of the Ha Nohana tracks help refine the properties of the substrate during track making, the ichnotaxonomic affinities of the footprints and the interpretation of the foot movement relative to the substrate. Two footprint morphotypes, ~ 300 m apart, are defined on the palaeosurface. Tracks of morphotype I are tridactyl, shallow, contain digital pad impressions and were impressed on a firm, sand rippled substrate that underwent desiccation. Conversely, tracks of morphotype II are tetradactyl, deep, and have an elongated posterior region. These tracks are preserved on the surface of a massive sandstone and are associated with soft sediment collapse structures related to the animal’s foot sinking into the water-saturated, malleable sediment layer. Morphotype II tracks show that as the animal waded across the substrate, the liquefied sediment lost its cohesive strength and could only partially support the weight of the animal. In so doing, the animal’s foot sunk deep enough into the sediment such that the impression of the metatarsal and digit I (hallux) are now visible. Thus, the palaeosurface was walked on by small-to-medium sized theropods that traversed over ripple marks in firmer moist sand, as well as a larger theropod that tottered through water-logged sand.
Źródło:
Annales Societatis Geologorum Poloniae; 2018, 88, 2; 163-179
0208-9068
Pojawia się w:
Annales Societatis Geologorum Poloniae
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Palaeozoic palaeogeography of the East European Craton (Poland) in the framework of global plate tectonics
Autorzy:
Golonka, Jan
Porębski, Szczepan J.
Barmuta, Jan
Papiernik, Jan
Bębenek, Sławomir
Barmuta, Maria
Botor, Mariusz
Pietsch, Kaja
Słomka, Tadeusz
Powiązania:
https://bibliotekanauki.pl/articles/191864.pdf
Data publikacji:
2019
Wydawca:
Polskie Towarzystwo Geologiczne
Tematy:
Palaeozoic
Baltica
Avalonia
Gondwana
Laurussia
plate tectonics
Opis:
Global palaeogeographic maps were constructed for eight time intervals in the Palaeozoic. The maps contain information concerning plate tectonics and palaeoenvironment during the Cambrian, Ordovician, Silurian, Devonian and Carboniferous. The East European Craton belonged to the Palaeozoic Baltica Plate, which originated as a result of disintegration of the supercontinent Pannotia during the early Cambrian. Baltica included part of Poland and adjacent areas northeast of a line that extends between Scania and the Black Sea. This plate was located in the Southern Hemisphere and drifted northward during Early Palaeozoic time. The Early Ordovician was the time of maximum dispersion of continents during the Palaeozoic. Avalonia probably started to drift away from Gondwana and moved towards Baltica during Ordovician time. Between Gondwana, Baltica, Avalonia and Laurentia, a large longitudinal oceanic unit, known as the Rheic Ocean, was formed. Avalonia was probably sutured to Baltica by the end of the Ordovician or in the Early Silurian. This process was dominated by the strike-slip suturing of the two continents, rather than a full-scale continent-continent collision. Silurian was a time of Caledonian orogeny, closing of the Early Palaeozoic oceans, collision of Baltica with Avalonia and Laurentia and the assembly of the supercontinent Laurussia. The Variscan orogeny in Poland was caused by the collision of the Bohemian Massif plates and the Protocarpathian terrane with Laurussia. The Protocarpathian terrane acted as an indentor that caused thrust tectonics in the East European Platform, Holy Cross Mountains and the Lublin area.
Źródło:
Annales Societatis Geologorum Poloniae; 2019, 89, 4; 381-403
0208-9068
Pojawia się w:
Annales Societatis Geologorum Poloniae
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-4 z 4

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