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GCAGS Transactions

Abstract


Gulf Coast Association of Geological Societies Transactions
Vol. 21 (1971), Pages 450-450

Abstract: Provincialism Among Mid-Eocene Calcareous Nannofossils

Laurel M. Bybell (1), Stefan Gartner, Jr (1)

ABSTRACT

The Middle Eocene Lisbon Formation of Alabama contains a rich and varied assemblage of pentaliths, members of the coccolith family Braarudosphaeridae. Similar pentalith assemblages are recorded from hemipelagic marine deposits in numerous areas, but are notably lacking in oceanic pelagic sediments. Pentaliths are rare in contemporary nannofloras, but several other Recent coccolithophores have a provincial distribution which is attributed primarily to a benthonic phase in the life cycle of the organism. Eocene Braarudosphaeridae may have had similar limitations; nevertheless, they must have possessed a phase which was capable of traversing the open ocean, since the same species occur in hemipelagic strata on all continents. These organisms either represent a non-calcifying phase, such as is known among modern coccolithophores, or their remains were not suitable for preservation in oceanic sediments. Alternatively, the open ocean representatives of the various pentalith species are entirely dissimilar and have remained unrecognized. This apparent provincialism does not diminish the usefulness of pentaliths, because the occurrence of a particular species is synchronous throughout the geographic range of that form. Thus, pentaliths are useful, both as stratigraphic indicators in Paleogene rocks, and as environmental indicators of the hemipelagic realm.

FOOTNOTE 2. Contribution from Rosenstiel School of Marine and Atmospheric Sciences, University of Miami.

EDITOR'S NOTE: Unfortunately the printer received this paper too late for the text to be included.

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ACKNOWLEDGMENTS AND ASSOCIATED FOOTNOTES

(1) Rosenstiel School of Marine and Atmospheric Sciences, University of Miami.

Miami, Florida 33149

Copyright © 1999 by The Gulf Coast Association of Geological Societies