Modern and Palaeoecological Significance of the Radiolarian Spongaster tetras tetras Ehrenberg in the Eastern Equatorial Pacifics |
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| Authors: | S K Haslett |
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| Institution: | Faculty of Applied Sciences, Bath College of Higher Education. Newton Park, Newton St. Loe. Bath, Avon, BA2 9BN, UK. |
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| Abstract: | Abstract. Spongaster tetras tetras Ehrenberg has long been considered by palaeontologists as a species indicative of warm (>21 C) sea-surface temperatures (SSTs) and tropical/subtropical conditions. However. a comparison of the Plio-Pleistocene record of S. t. tetras in the eastern equatorial Pacific (Ocean Drilling Program Hole 677A) with CaCO3, δ18O, and δ13C records reveals that S. t. tetras is most commonly present during periods of intense upwelling, often coinciding with isotopically identified glacial stages. when surface productivity and salinity are high, and SST is expected to be relatively low. Maximum S. t. tetras abundance (1.8% of radiolaria counted) occurred during a cool interglacial. when productivity and salinity were high, wind-driven upwelling intense, and SST relatively warmer than during glacial maxima. It appears that in the eastern equatorial Pacific upwelling system, SSTs are generally too cold (<21 C) for S. t. tetras to survive; however, S. t. tetras can tolerate (with populations <0.7%) cold SSTs if productivity and salinity are increased (due to upwelling), and flourishes (>0.7–> 1.8%) if this is coupled with relatively warm SSTs. This micropalaeontological study Corroborates the findings of an earlier research program on living S. t. tetras cultures (Anderson et al ., 1989a.b, c). |
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| Keywords: | Radiolaria Pliocene-Pleistocene palaeoecology Pacific palaeoceanography |
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