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Wyszukujesz frazę "Middle Tremadocian" wg kryterium: Wszystkie pola


Wyświetlanie 1-2 z 2
Tytuł:
Origin of hydrocarbon gases accumulated in the Middle Cambrian reservoirs of the Polish part of the Baltic region
Autorzy:
Kotarba, M. J.
Powiązania:
https://bibliotekanauki.pl/articles/2059071.pdf
Data publikacji:
2010
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
Polish Baltic Sea region
Upper Cambrian-Tremadocian source rock succession
thermogenic gases
microbial methane
hydrous pyrolysis
stable isotopes
Opis:
The origin of natural gases associated with oil and condensate accumulations within the Middle Cambrian sandstone reservoirs on the Polish part of the Baltic region was characterized by means of molecular analyses, stable carbon isotopes of methane, ethane and propane, and stable hydrogen isotopes of methane. Gases generated from the Upper Cambrian-Tremadocian source rock succession by hydrous pyrolysis at 330°C for 72 h was used to characterize thermogenic gas and to identify the microbial methane input in the natural gas accumulations. A insignificant component of microbial methane is only present in gases from the B3 offshore field and from two inflows in the B7-1/91 borehole. The traps within the Middle Cambrian sandstone reservoirs had already been formed and sealed between the Late Cambrian and the Early Ordovician time span when migration of microbial methane took place along the fault system. The traps were successively supplied with thermogenic gaseous hydrocarbons, condensate and oil generated from the same source organic matter of the Upper Cambrian-Tremadocian source rock succession at a successively higher maturation stage.
Źródło:
Geological Quarterly; 2010, 54, 2; 197-204
1641-7291
Pojawia się w:
Geological Quarterly
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A new genus of middle Tremadocian orthoceratoids and the Early Ordovician origin of orthoceratoid cephalopods
Autorzy:
Kroger, B.
Powiązania:
https://bibliotekanauki.pl/articles/22312.pdf
Data publikacji:
2008
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
new genus
Middle Tremadocian
orthoceratoid
Early Ordovician
Orthoceratoidea
cephalopod
remains
Orthocerida
Orthoceratoidae
Opis:
The cephalopods of the subclass Orthoceratoidea, which are termed “orthoceratoids” herein, are a group that remains “the last unexplored wilderness in the Cephalopoda” (Flower 1962: 23). After 45 years this statement still holds true because phylogeny reconstructions are hindered by their morphological simplicity, numerous homeomorphies and iterative evolution. The Orthocerida, straight cephalopods that are characterised by a wide chamber spacing, a thin tubular siphuncle and a small spherical initial chamber, lacking a cicatrix (Kröger 2006) were the ancestors of bactritoids, ammonoids, and coleoids (Engeser 1996). The origin of the Orthocerida is poorly understood. The earliest unequivocal Orthocerida are known from the Floian (Early Ordovician). A number of poorly known possible Orthocerida and/or stem group Orthocerida are known from the Tremadocian. Here, I reassign the long known middle Tremadocian “Orthoceras attavus” to the new genus Slemmestadoceras belonging to a group of worldwide distributed orthoceratoids. The presence of Slemmestadoceras with a thin, probable tubular siphuncle and small initial chambers in the middle Tremadocian suggests that the Orthocerida may have originated already at that time. The comparison of Slemmestadoceras with following late Tremadocian and Floian orthoceratoids demonstrates that a higher level taxon comprising these forms, such as the subclass Orthoceratoidea may constitute a paraphylum.
Źródło:
Acta Palaeontologica Polonica; 2008, 53, 4
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-2 z 2

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