Jere H. Lipps, 1979. "Ecology and Paleoecology of Planktic Foraminifera", Foraminiferal Ecology and Paleoecology, Jere H. Lipps, Wolfgang H. Berger, Martin A. Buzas, Robert G. Douglas, Charles A. Ross
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Planktic foraminifera have been studied in detail for over a hundred years. During this time, they have been useful for biostratigraphic correlation of Cretaceous and younger deep water facies and for paleooceanographic inference. Their paleoecologic utility has been more limited, perhaps because it is based primarily on empirical comparisons of fossils with modern species occurrences. The first planktic species possibly occurred in the Triassic and by the Jurassic, simple globigeriniform species were present in tropical seas. Iterative evolution thereafter produced recurring radiations of high diversity, morphologically complex faunas interspersed with low diversity, morphologically simple faunas.
Test morphology can be interpreted as adaptations for main enance of position in the water column, defense against predators, or maintenance of a preferred orientation. Of these, water column positioning is likely to be most critical. Test morphologies may function in relation to density of the foraminiferan and its difference with water, resistance to sinking, and turbulence.
The biology and paleobiology of planktic species is poorly known, These foraminifera probably utilize different feeding, reproductive, behavioral, and life history strategies in eutrophic and oligotrophic waters. Mostof these strategies can be inferred from fossils, and therefore have considerable paleoecologic potential. Biogeographic distributions are most commonly used for paleoecology, yet it is very difficult to explain these patterns not only for foraminifera, but for other plankton as well. Six hypotheses are considered. The patterns are not determined by temperature, salinity or circulation alone, nor do they match water mass boundaries wellbecause of mixing along the edges. The idea of “core” ecosystems of more or less fixed biotic structure surrounded by wide ecotones of variable conditions and structure is supported by plankton and foraminiferal evidence. A non-exclusive hypothesis is that environmental stability or lack of it is influential in producing faunal compositions. Bipolar species may be maintained by mixing, coiling directions do not depend on temperature, and distributions on continental shelves are complex but related in general to oceanic water and depth.
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Foraminiferal Ecology and Paleoecology
Perhaps no fossil group is used as much as foraminifera for paleoecologic inference, both in academia and industry. Since the late 1960s, new concepts and much additional data have appeared that make it difficult for the casual worker not immediately concerned with foraminiferal ecology and paleoecology to stay abreast of the latest developments. In these notes, the authors summarize much of that information, or provide reference to more detailed sources. They also attempt to point out problems and other methods of dealing with them. Most paleoecologic work with foraminifera in the past has relied on direct comparison of fossil assemblages with the most similar modern assemblages, and inferring then that the environments were similar also. The method is used widely in scientific studies and in industrial applications. The result is based on the single hypothesis that the fossils are environmentally analogous to their modern counterparts. These notes present a number of alternative working hypotheses, and in some cases, examine the data to attempt of disprove them.