1,721,566 research outputs found
(Table 1) Oxygen and carbon isotopic composition of Globigerina altispira in DSDP Site 30-289, Western Equatorial Pacific
No full text(Table 1) Oxygen and carbon isotopic composition of Globigerina altispira in DSDP Site 30-289, Western Equatorial Pacifi
(Table 2) Oxygen and carbon isotopic composition of benthic and planktic foraminifera of samples from DSDP Site 30-289 in core 55, Western Equatorial Pacific
No full text(Table 2) Oxygen and carbon isotopic composition of benthic and planktic foraminifera of samples from DSDP Site 30-289 in core 55, Western Equatorial Pacifi
Nannofossil evolutionary events in the mid-Pliocene: an assessment of the degree of synchrony in the extinctions of Reticulofenestra pseudoumbilicus and Sphenolithus abies
No full textThe mid-Pliocene was an interval of subtle reorganisation within the nannoplankton community, including the prominent and biostratigraphically important last occurrences of Sphenolithus abies and Reticulofenestra pseudoumbilicus. The transition is part of the Pliocene to Recent ‘attrition’ of nannofossil species that resulted from changes in the distribution of trophic resources, and deep-water and surface-water current systems, likely associated with the initiation of Northern Hemisphere glaciation.The extinctions of Sphenolithus abies and Reticulofenestra pseudoumbilicus were analysed in detail at ODP Sites 659, 662, and 926 in the equatorial and subequatorial Atlantic. These taxa show significantly different patterns of duration and timing of decline based on high-resolution abundance records and calibration with oxygen isotope stratigraphy. The initiation of abundance decline between 3.71 and 3.67 Ma and the extinction of S. abies between 3.56 and 3.52 Ma are diachronous. This extinction may have been a response to the intensification of glacial intervals at this time. In contrast, the last occurrence of R. pseudoumbilicus at 3.81–3.82 Ma appears to be a valid example of biostratigraphic (although not necessarily biological) synchrony in the fossil record. Direct environmental forcing is not attributable for the extinction of R. pseudoumbilicus; however, indirect physical and/or biological environmental stress may explain the observed patterns
Stable isotope analysis on sediment core RC11-86
No full textOxygen isotope measurements have been made in foraminifera from over 60 deep-sea sediment cores. Taken together with the oxygen isotope measurements published by Emiliani from Caribbean and Equatorial Atlantic cores, this comprises a unique body of stratigraphic data covering most of the important areas of calcareous sediment over the whole world ocean. The oxygen isotopic composition of foraminifera from cores of Late Pleistocene sediment varies in a similar manner in nearly all areas; the variations reflect changes in the oxygen isotopic composition of the ocean. The oceans are mixed in about 1 ka so that ocean isotopic changes, resulting from fluctuations in the quantity of ice stored on the continents, must have occurred almost synchronously in all regions. Thus the oxygen isotope record provides an excellent means of stratigraphic correlation. Cores accumulated at rates of over about 5 cm/ka provide records of oxygen isotopic composition change that are almost unaffected by post-depositional mixing of the sediment. Thus they preserve a detailed record of the advance and retreat of the ice masses in the northern hemisphere, and provide a unique source of information for the study of ice-sheet dynamics
(Table 5) Stable carbon and oxygen isotope ratios of benthic foraminifera from sediment core GIK12392-1 in the eastern Atlantic Ocean
No full text(Table 5) Stable carbon and oxygen isotope ratios of benthic foraminifera from sediment core GIK12392-1 in the eastern Atlantic Ocea
(Table 6) Stable carbon and oxygen isotope ratios of Uvigerina peregrina from sediment core Y71-06-12 in the Atlantic Ocean
No full text(Table 6) Stable carbon and oxygen isotope ratios of Uvigerina peregrina from sediment core Y71-06-12 in the Atlantic Ocea
(Table 4) Stable oxygen isotope ratios of Globigerinoides sacculifer from sediment core RC17-177
No full text(Table 4) Stable oxygen isotope ratios of Globigerinoides sacculifer from sediment core RC17-17
Stable carbon isotopes of Planulina wuellerstorfi of sediment core MD99-2334
No full textStable carbon isotopes of Planulina wuellerstorfi of sediment core MD99-233
(Table 5) Age model of sediment core RC17-177
No full text(Table 5) Age model of sediment core RC17-17
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