257 resultados para Abathomphalus intermedius


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Studies of diatoms from dredge samples collected on the island slope of the Kuril-Kamchatka Trench have allowed to recognize well-preserved marine diatom assemblages corresponding to assemblages of the followed Oligocene zones: Rhizosolenia oligocaenica (subzone ''a'', 33.6-31 Ma), Cavitatus rectus (29.6-28.2 Ma), and Rocella gelida (28.2-24.0 Ma) as identified in the North Pacific zonal scale. Description of these assemblages and their complete taxonomic composition are presented. Diversity of species together with abundance and degree of preservation of diatoms and accompanying siliceous microorganisms suggests their autochtonous origin and favorable conditions of their development. Assemblages of the Early Oligocene zones Rhizosolenia oligocaenica and Cavitatus rectus recognized in sediments of the outer zone of the Lesser Kuril Ridge (submarine slope of the Shikotan Island) and on the Vityaz' submarine ridge were most probably formed under conditions of a vast shelf, while assemblage of the Late Oligocene zone Rocella gelida encountered only in the region of the Lesser Kuril Ridge formed under more deep-water conditions, presumably, over an island slope. Deepening of the basin in the region of the outer zone of the Lesser Kuril Ridge in Late Oligocene probably reflects one of stages of evolution of the Kuril-Kamchatka Trench.

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Über die Verbreitung, Gliederung und Ausbildung des Jungtertiärs im westlichen Schleswig-Holstein war bisher nicht viel bekannt. Am besten bearbeitet sind die glazial gestauchten Schollen von Morsum/Sylt. Eine Aufzählung erbohrter Miozänvorkommen mit nicht immer überzeugender Begründung lieferte H.-L. HECK 1935. S. THIELE (1941) hat die ihm bekannten Vorkommen hauptsächlich nach faziellen und petrographischen Gesichtspunkten bearbeitet. Er erkannte richtig die Stellung der Braunkohlensande. Die angekündigte palaeontologische Bearbeitung ist nicht erschienen. Eine allgemeine Übersicht über die Entwicklung des Jungtertiärs bringen W. WOLFE und H.-L. HECK 1949. W. HINSCH lieferte wertvolle Beiträge zur Molluskenfauna und zur Gliederung des Miozäns (1952, 1955). Über neue Vorkommen von Braunkohlen-Sanden berichtete E. DITTMER(1 956), eine erste Übersicht über neue Vorkommen der Hemmoorer Stufe gab derselbe Verfasser 1957.

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The family Munnopsidae was the most abundant and diverse among 22 isopod families collected by the ANDEEP deep-sea expeditions in 2002 and 2005 in the Atlantic sector of the Southern Ocean. A total of 219 species from 31 genera and eight subfamilies were analysed. Only 20% species were known to science, and 11% of these were reported outside the ANDEEP area mainly from other parts of the SO or the South Atlantic deep sea. One hundred and five species (50%) were rare, occurring at only 1 or 2 stations. Seventy-two percent of all munnopsid specimens belong to the most numerous 25 species with a total abundance of more than 75 specimens; 5 of these species (40% of all specimens) belong to the main genera of the world munnopsid fauna, Eurycope, Disconectes, Betamorpha, and Ilyarachna. About half of all munnopsid specimens and 34% of all species belong to the subfamily Eurycopinae, which is followed in occurrence by the Lipomerinae (19%). Munnopsinae is the poorest represented subfamily (1.5%). The composition of the subfamilies for the munnopsid fauna of the ANDEEP area differs from that of northern faunas. Lipomerinae show a lower percentage (7%) in the North Atlantic and are absent in the Arctic and in the North Pacific. This subfamily is considered as young and having a centre of origin and diversification in the Southern Ocean. The analyses of the taxonomic diversity and the distribution of Antarctic munnopsids and the distribution of the world fauna of all genera of the family revealed that species richness and diversity of the genera are highest in the ANDEEP area. The investigated fauna is characterised also by high percentage of endemic species, the highest richness and diversity of the main munnopsid genera and subfamily Lipomerinae. This supports the hypothesis that the Atlantic sector of SO deep sea may be considered as the main contemporary centre of diversification of the Munnopsidae. It might serve as a diversity pump of species of the Munnopsidae to more northern Atlantic areas via the deep water originating in the Weddell Sea.

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Drilling on the Iberia Abyssal Plain during Ocean Drilling Program Leg 173 allowed us to recover Upper Cretaceous through Paleocene sediments at Sites 1068 and 1069 and only upper Paleocene sediments at Site 1067, which expands considerably the Upper Cretaceous to Paleocene record for this region. Of these three sites, Site 1068 recovered uppermost Cretaceous sediments as well as the most complete Paleocene record, whereas Site 1067 yielded only uppermost Paleocene sediments (Zone CP8). Site 1069 provided a rather complete upper Campanian through Maastrichtian section but a discontinuous Paleocene record. After a detailed calcareous nannofossil biostratigraphy was documented in distribution charts, we calculated mass accumulation rates for Holes 1068A and 1069A. Sediments in Hole 1068A apparently record the final stages of burial of a high basement block by turbidity flows. Accumulation rates through the Upper Cretaceous indicate relatively high rates, 0.95 g/cm**2/k.y., but may be unreliable because of the lack of datum points and/or possible hiatuses. Accumulation rates in the Paleocene section of Hole 1068A fluctuated every few million years from lower (~0.35 g/cm**2/k.y.) to higher rates (~0.85 g/cm**2/k.y.) until the latest Paleocene, when rates increased to an average of ~2.0 g/cm**2/k.y. Mass accumulation rates for the Upper Cretaceous in Hole 1069A indicate a steady rate of ~0.60 g/cm**2/k.y. from 75 to 72 Ma. There may have been one or more hiatuses between 72 and 68 Ma (combined Zone CC24 through Subzone CC25b), as indicated by the very low accumulation rate of 0.15 g/cm**2/k.y. The Paleocene section of Hole 1069A does not show the same continuous record, which may result from fluctuations in the carbonate compensation depth and poor recovery (average = 40%). Zones CP4 and CP5 are missing within a barren interval; this and numerous other barren intervals affect the precision of the nannofossil zonation and calculation of mass accumulation rates. However, in spite of these missing zones, mass accumulation rates do not seem to indicate the presence of hiatuses as the rates for this barren interval average ~1.0 g/cm**2/k.y. This study set out to test the hypothesis that a reliable biostratigraphic record could be constructed from sediments derived from turbidity flows deposited below the carbonate compensation depth. As illustrated here, not only could a reliable biostratigraphic record be determined from these sediments, but sedimentation and mass accumulation rates could also be determined, allowing inferences to be drawn concerning the sedimentary history of this passive margin. The reliability of this record is confirmed by independent verification by the establishment of a magnetostratigraphy for the same cores.