نتایج جستجو برای: foraminifera
تعداد نتایج: 4350 فیلتر نتایج به سال:
During the 2004 summer season, 14 sediment samples were collected in Kongs− fjorden and Isfjorden, West Spitsbergen, from 6 down to 345 m water−depth (mwd). The samples yielded abundant assemblage of monothalamous foraminifera, belonging to almost 40 morphotypes. Our qualitative (>125 μm) and quantitative data (125–500 μm) allowed to distinguish three water−depth related assemblages in both Kon...
The plasmodiophorids are a group of eukaryotic intracellular parasites that cause disease in a variety of economically significant crops. Plasmodiophorids have traditionally been considered fungi but have more recently been suggested to be members of the Cercozoa, a morphologically diverse group of amoeboid, flagellate, and amoeboflagellate protists. The recognition that Cercozoa constitute a m...
Ammonites are among the best-known fossils of the Phanerozoic, yet their habitat is poorly understood. Three common ammonite families (Baculitidae, Scaphitidae, and Sphenodiscidae) co-occur with well-preserved planktonic and benthic organisms at the type locality of the upper Maastrichtian Owl Creek Formation, offering an excellent opportunity to constrain their depth habitats through isotopic ...
Monothalamous (single-chambered) foraminifera have long been considered as the "poor cousins" of multichambered species, which calcareous and agglutinated tests dominate in the fossil record. This view is currently changing with environmental DNA surveys showing that the monothalamids may be as diverse as hard-shelled foraminifera. Yet, the majority of numerous molecular lineages revealed by eD...
Changes in both silicate weathering rates and organic carbon burial have been proposed as drivers of the transient “Mi-1” glaciation event at the Oligocene-Miocene transition (OMT; ~23 Ma). However, detailed geochemical proxy data are required to test these hypotheses. Here we present records of Li/Ca, Mg/Ca, Cd/Ca, U/Ca, δO, δC, and shell weight in planktonic foraminifera from marine sediments...
The discovery that foraminifera are able to use nitrate instead of oxygen as an electron acceptor for respiration has challenged our understanding of nitrogen cycling in the ocean. It was thought before that only prokaryotes and some fungi are able to denitrify. Rate estimates of foraminiferal denitrification have been very sparse and limited to specific regions in the oceans, not comparing sta...
Coral reefs are now subject to global threats and influences from numerous anthropogenic sources. Foraminifera, a group of unicellular shelled organisms, are excellent indicators of water quality and reef health. Thus we studied a set of samples taken in 1992 to provide a foraminiferal baseline for future studies of environmental change. Our study provides the first island-wide analysis of shal...
the upper cretaceous thick bedded succession in badamouyeh mountain in honooj area shows the late cenomanian-santonian stages. also, these deposits are well exposed in the south-west of bibihayat and south of cheshmah gaz village. in the studied section, lower and upper honooj green marls (informal) with intercalation of exogyroferous shaly limestone are overlain by thick bedded limestones and ...
Planktonic Foraminifera are a major contributor to the deep carbonate flux and their microfossil deposits form one of the richest databases for reconstructing paleoenvironments, particularly through changes in their taxonomic and shell composition. Using an empirically based planktonic foraminifer model that incorporates three known major physiological drivers of their biogeography – temperatur...
The geochemical composition of foraminiferal tests is a valuable archive for the reconstruction of paleo-climatic, -oceanographic and -ecological changes. However, dissolution of biogenic calcite and precipitation of inorganic calcite (overgrowth and recrystallization) at the seafloor and in the sediment column can potentially alter the original geochemical composition of the foraminiferal test...
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