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Wyszukujesz frazę "Antarctic Peninsula" wg kryterium: Temat


Wyświetlanie 1-2 z 2
Tytuł:
Palaeomagnetism of Late Cretaceous-Paleocene igneous rocks from the western part of the Antarctic Peninsula (Argentine Islands Archipelago)
Autorzy:
Bakhmutov, V.
Shpyra, V.
Powiązania:
https://bibliotekanauki.pl/articles/2058740.pdf
Data publikacji:
2011
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
Cretaceous
Paleocene
Antarctic Peninsula
palaeomagnetism
Opis:
A collection of 360 oriented samples of igneous rocks from the western part of the Antarctic Peninsula (Argentine Islands Archipelago, Penola Strait area), has yielded well-defined palaeomagnetic directions. Age determinations by various methods showed a Late Cretaceous-Paleocene time interval for the rocks studied. The characteristic remanent magnetisation (ChRM) was isolated by a stepwise thermal demagnetisation mostly in the temperature interval 450-580 degreesC. It is evidently a primary magnetisation. The rocks along the coastline of the western part of the Antarctic Peninsula (AP) were emplaced during the Cretaceous Normal Superchron while the rocks from the islands with reversed polarity are of Paleocene. New Cretaceous (112-85 Ma) and Paleocene (60 Ma) palaeomagnetic poles for the passive continental margin of the Antarctic Peninsula fit well with a synthetic East Antarctica apparent polar wander path and confirms that the AP did not undergo latitudinal displacement for the last 100 Ma. The palaeomagnetic pole for 60 Ma shows a slight shift from palaeopoles obtained for the South Shetland Islands which implies that the South Shetland block is characterized by own tectonic evolution and probable anticlockwise rotation during the Paleocene.
Źródło:
Geological Quarterly; 2011, 55, 4; 285-300
1641-7291
Pojawia się w:
Geological Quarterly
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Eocene bryozoan assemblages from the La Meseta Formation of Seymour Island, Antarctica
Autorzy:
Hara, U.
Mörs, T.
Hagström, J.
Requero, M. A.
Powiązania:
https://bibliotekanauki.pl/articles/2060414.pdf
Data publikacji:
2018
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
Cyclostomata
Cheilostomata
taxonomy
Paleogene
James Ross Basin
Antarctic Peninsula
Opis:
Early to Late Eocene bryozoans from the La Meseta Formation of Seymour Island were collected at two localities within the Cucullaea I Allomember (Telm4 and Telm5) on the northwestern side of the island and in two localities within the Submeseta Allomember (Telm6 and Telm7) on the northeastern side. This fauna is represented by cyclostomes of the suborders Tubuliporina and Cerioporina and suborders of Neocheilostomata, among which nine species have been recognized. The following new species are introduced: Micropora nordenskjoeldi sp. nov., Lunulites marambionis sp. nov., Otionellina antarctica sp. nov. and Otionellina eocenica sp. nov. Some other taxa recognized in the studied material, such as Reticrescis plicatus, Uharella seymourensis and Celleporaria mesetaensis, were previously described from the lowermost (Telm1) or uppermost parts (Telm6-7), thus their stratigraphical ranges within the La Meseta Formation are extended. The diverse growth-forms of the bryozoans include a sole ball-shaped celleporiform colony and reticulated and bilamellar-foliaceous colony, as well as rich encrusting and free-living forms (so-called sand faunas), indicating the existence of locally restricted shallow-marine environments. This is particularly true in the middle and upper parts of the La Meseta Formation (Telm4-7). Reticulated, spheroidal and robust, branched colonies, which thrived in the environmental conditions of the lower part (Telm1), are represented only by a sparse bryozoan biota in the upper part of the La Meseta Formation. Lunulitiforms, such as Lunulites and Otionellina which are warm water, free-living bryozoans, dominate in the siliciclastic sediments of Telm5, but erect folded sheets forming a shell bed composed of ?Goodonia occur in Telm6-7. These three genera are recognized in Antarctica for the first time. The austral genus Otionellina has its earliest fossil record here, showing close biogeographical links with the Late Eocene-Miocene faunas of Australia and New Zealand. The taxonomic composition of the studied fauna together with their growth forms is a very good tool for reconstructing palaeoenvironmental conditions in the middle and upper parts (Telm4-7) of the La Meseta Formation, deposited during the Late Ypresian-Priabonian.
Źródło:
Geological Quarterly; 2018, 62, 3; 705--728
1641-7291
Pojawia się w:
Geological Quarterly
Dostawca treści:
Biblioteka Nauki
Artykuł
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