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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 65 (1981)

Issue: 5. (May)

First Page: 987

Last Page: 987

Title: Cenozoic Deep-Water Benthic Foraminifers: ABSTRACT

Author(s): Detmar Schnitker

Article Type: Meeting abstract


Cenozoic deep water deposits have yielded rich and diversified faunas of benthic formaminifers. From still limited data, it is clear than these faunas were depth stratified and that most species were cosmopolitan in distribution. The wide distribution and species richness, together with faunal turnover, which in places was very abrupt, points to great biostratigraphic potential. High turnovers delineate distinct Paleocene, Eocene, and Oligocene-early Miocene faunas. A gradual but profound wave of extinction and speciation occurred during the middle Miocene and by late Micene had created the modern deep water faunas.

Superimposed upon these evolutionary developments are strong changes in depth preference, particularly among those species that persist across the turnover periods. During the Paleocene-Eocene transition some species became restricted to the bathyal realm while others preferred the abyss. During the Eocene-Oligocene transition a net downward depth range extension of bathyal species occurred. During the late Miocene the periodic vertical migrations of bathyal and abyssal faunas that so strongly characterize the Quaternary began to appear. In the North Atlantic, such depth range excursions may extend over more than 1,500 m.

The evolutionary and bathymetric changes of benthic faunas are their response to the evolution of the deep water environment, particularly the establishment of the cold water sphere during the late Eocene, and the addition of the North Atlantic as a source of cold water during the middle Miocene. The late Cenozoic depth changes are indicative of periodic rearrangements of the deep ocean circulation in response to climatic change at the earth's surface.

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