نتایج جستجو برای: keywords foraminifera
تعداد نتایج: 1981950 فیلتر نتایج به سال:
Deposits spanning the Radotruncana calcarata Taxon Range Zone at the Postalm section, Northern Calcareous Alps (Austria) are examined quantitatively for foraminiferal assemblages, especially the planktonic group. This study focuses on establishing a high resolution record spanning an 800 ka long stratigraphic interval from the active continental margin of the Penninic Ocean. The Postalm section...
We present stable isotope and geochemical data from four sediment cores from west of Prins Karls Forland (ca. 340 m water depth), offshore western Svalbard, recovered from close to sites of active methane seepage, as well as from shallower water depths where methane seepage is not presently observed. Our analyses provide insight into the record of methane seepage in an area where ongoing ocean ...
Cifelli, Richard. Textural Observations on Some Living Species of Planktonic Foraminifera. Smithsonian Contributions to Paleobiology, n u m b e r 45, 45 pages, 15 plates, 1982.—Wall textures of 11 species of spinose and quasi-spinose planktonic foraminifera collected in plankton tows from the Nor th and Equator ia l Atlantic have been studied with the scanning electron microscope. Il lustration...
Species-range expansions are a predicted and realized consequence of global climate change. Climate warming and the poleward widening of the tropical belt have induced range shifts in a variety of marine and terrestrial species. Range expansions may have broad implications on native biota and ecosystem functioning as shifting species may perturb recipient communities. Larger symbiont-bearing fo...
Specimens of Recent foraminifera of Amphistegina radiata, Peneroplis planatus and Globigerinoides ruber, from fifty samples of surface sediments of the continental margin of the State of Ceará, Brazil, have been analyzed for carbon and oxygen isotopes to investigate oceanographic parameters and determine the values of delta18O of the oceanic water. From a comparison between values of delta18O o...
Molecular phylogenies of foraminifera are commonly inferred from the small subunit rRNA (SSU) genes, which can easily be obtained from single cells isolated from environmental samples. The SSU phylogenies, however, are often biased by heterogeneity of substitution rates, and their resolution of higher level relationships is often very low. The sequences of protein-coding genes provide an import...
Foraminifera are unicellular organisms that inhabit the oceans in various ecosystems. The majority of the foraminifera precipitate calcitic shells and are among the major CaCO(3) producers in the oceans. They comprise an important component of the global carbon cycle and also provide valuable paleoceanographic information based on the relative abundance of stable isotopes and trace elements (pr...
The larger benthic foraminifera Gyroconulina columellifera Schroeder & Darmoian, 1977 (type-locality: Maastrichtian Aqra Formation of Iraq) is described for the first time from two sections of the Maastrichtian Tarbur Formation of the Zagros Fold-Thrust-Belt, SW Iran. New details on its wall microstructure are provided. The microfacies is represented by bioclastic wacke-/pack-/grainstones with ...
There is general agreement that productivity in high latitudes increased in the late Eocene and remained high in the early Oligocene. Evidence for both increased and decreased productivity across the Eocene-Oligocene transition (EOT) in the tropics has been presented, usually based on only one paleoproductivity proxy and often in sites with incomplete recovery of the EOT itself. A complete reco...
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