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On-line version ISSN 1678-2690
An. Acad. Bras. Ciênc. vol.74 no.2 Rio de Janeiro June 2002
RHABDOSPHAERA CLAVIGERA (CALCAREOUS NANNOFOSSILS) AS PALEOTEMPERATURE INDICATORS: A COMPARISON WITH ISOTOPIC DATA
MARIA DOLORES WANDERLEY 1 AND JERRY F. MCMANUS 2
1 LabMicro / Depto de Geologia / IGEO / UFRJ - Rio de Janeiro - Brazil.
2 Woods Hole Oceanographic Institution, Woods Hole, MA - USA.
Presented by DIOGENES DE ALMEIDA CAMPOS
The content of nannofossils and O18/O16 isotopic analysis on foraminifer carapaces of the sample (multicore) MC-58 was studied. The purpose of this project was to compare quantitative data of the species Rhabdosphaera clavigera (calcareous nannofossil) with O18/O16 isotopic information. The material was collected by the researchers of the Woods Hole Oceanographic Institution in a joint program with the LAGEMAR-UFF at the sea route 159-5 and was posteriorly deposited in the Laboratório de Micropaleontologia (LabMicro) of the Geology Department/UFRJ. The sample (multicore) MC-58 has a Pleistocene/Holocene age and is situated on the São Paulo Plateau (continental margin of southeastern Brazil) at a depth of 4,015m. Among the 23 nannofossil species found, Rhabdosphaera clavigera is quite common and about 240 individuals of this taxon were recovered. This species is considered an indicator of tropical waters since it is abundant in waters with a temperature of 18.3ºC. The present study showed that there is a strong correlation between the abundance of R. clavigera and decreasing isotopic values of O18/O16, confirming the paleoecological interpretation proposed for this species. ( December 20, 2001 ).