نتایج جستجو برای: foraminifera
تعداد نتایج: 4350 فیلتر نتایج به سال:
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...
New and poorly known Middle Jurassic larger benthic foraminifera from the Karst Dinarides of Croatia
Some new and poorly known larger benthic foraminifera are described from Middle Jurassic (Upper Aalenian–Bajocian) shallow-water limestones of the Croatian Karst Dinarides. Cymbriaella lorigae FUGAGNOLI is reported for the fi rst time outside its type-locality, the Upper Pliensbachian of the Southern Alps. New taxa described include Bosniella bassoulleti n. sp. and Dubrovnikella septfontainei n...
Difficulties remain with theoretical explanations of the apparent reduced zonal sea surface temperature gradient in the tropical Pacific of the Pliocene. One favored hypothesis is that it was a ‘‘permanent El Niño’’ state, with the warm phase of ENSO remaining fixed over millions of years. Here, an alternative is suggested— that there was a ‘‘perpetually running ENSO’’ with a shorter return tim...
Study of a late Late Santonian to Late Campanian hemipelagic succession from Abtalkh Formation at the Bahadorkhan section (Central Kopet-Dagh) enabled us to verify paleoecology changes based on planktonic and benthic foraminifera assemblage. Bahadorkhan section is consisted of calcareous shale, lime marl, marl, and a few dispersed chalky limestone beds. Upper and lower boundaries of Abtalkh For...
the qom formation in ghohrud area, have been investigated in order to determine its biostratigraphy and palaeoecology. the thickness of qom formation is 325 meters at the study area and consists of thin, medium to thick bedded and massive limestons. they underline on eocene volcanic with disconformably and its upper boundary is overlain by alluvium. based on thin section studies 14 genera and 2...
Difficulties remain with theoretical explanations of the apparent reduced zonal sea surface temperature gradient in the tropical Pacific of the Pliocene. One favored hypothesis is that it was a ‘‘permanent El Niño’’ state, with the warm phase of ENSO remaining fixed over millions of years. Here, an alternative is suggested— that there was a ‘‘perpetually running ENSO’’ with a shorter return tim...
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