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Geological Society, London, Special Publications; 1992; v. 64; p. 77-91;
DOI: 10.1144/GSL.SP.1992.064.01.05
© 1992 Geological Society of London

Modern Upwelling Systems and Palaeo-Upwelling Criteria

Planktonic foraminiferal faunal and stable isotopic indices of upwelling: a sediment trap study in the San Pedro Basin, Southern California Bight

Robert Thunell1 & Leslie Reynolds Sautter2

1 Department of Geological Sciences, University of South Carolina, Columbia, South Carolina 29208, USA
2 Lamont-Doherty Geological Observatory, Palisades, New York 10964, USA

A planktonic foraminiferal faunal and stable isotopic study has been carried out on sediment trap samples collected in 1988 from the San Pedro Basin (Southern California Bight) in order to examine the response of this group of plankton to coastal upwelling. Hydrographic monitoring indicates that a period of upwelling occurred in the basin from late April to early June, with a brief spring bloom of planktonic foraminifera occurring prior to upwelling. The onset of upwelling resulted in a significant increase in total foraminiferal shell flux; the upwelling assemblage was initially dominated by Globigerina quinqueloba, with Globigerina bulloides dominating the latter half of upwelling. Following upwelling, the upper water column became thermally stratified and Neogloboquadrina dutertrei dominated the fauna. The observed pattern of faunal succession may be partly related to changes in food availability.

Stable isotope analyses ({delta}18O and {delta}13C) of Neogloboquadrina pachyderma, N. dutertrei and G. bulloides indicate that all three species adjust their depth habitats in response to upwelling. Globigerina bulloides migrates from below the thermocline to the surface at the onset of upwelling. Both N. pachyderma and N. dutertrei appear to adjust their depth habitats in order to remain within specific temperature ranges.





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F. J. C. Peeters and G.-J. A. Brummer
The seasonal and vertical distribution of living planktic foraminifera in the NW Arabian Sea
Geological Society, London, Special Publications, 2002; 195: 463 - 497.
[Abstract] [PDF]