Changes in size and test porosity of Orbulina universa d'Orbigny in the Pleistocene record of Cape Bojador (DSDP Site 397, eastern North Atlantic)
1980; Elsevier BV; Volume: 5; Linguagem: Inglês
10.1016/0377-8398(80)90004-3
ISSN1872-6186
AutoresMaria Rosa Colombo, Maria Bianca Cita,
Tópico(s)Paleontology and Stratigraphy of Fossils
ResumoMeasurements of the diameter of O. universa carried out on 30 specimens from 39 samples covering a sediment thickness of 78 m and going back in time to approximately 750 000 y resulted in the construction of a curve of the mean diameter and a curve of the maximum diameter. Both curves, as well as those calculated with the running-averages technique, display cyclic fluctuations with durations of the order of 100 000 y and downwards decreasing amplitudes. These curves are compared with a carbonate curve (on bulk sediment) and an isotopic curve (on benthic foraminifers) obtained from the same set of samples. Correlations are fair to good, but a time-lag is noticed between the isotopic curve and the faunal (O. universa mean diameter) curve, with the isotopic signal coming first, in the middle part of the Brunhes Epoch. Biostratigraphic calibration to the paleomagnetic record is provided by four datum planes (two based on calcareous nannofossils, two on diatoms) identified in the succession. Changes recorded in test porosity seem to be less meaningful than changes in test size.
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