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Oligocene Neritic Foraminifera in Southern Australia: Spatiotemporal Biotic Patterns Reflect Sequence-Stratigraphic Environmental Patterns

By
Graham Moss
Graham Moss
Institute for Geophysics, University of Texas at Austin, Austin, Texas 78759-8500, U.S.A.
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Brian Mcgowran
Brian Mcgowran
Department of Geology and Geophysics, Adelaide University, Adelaide, South Australia 5005, Australia
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Published:
January 01, 2003

Abstract

Quantitative analysis of Oligocene assemblages in cool-water carbonates suggests a two-tiered response by benthic, neritic foraminiferal faunas to a succession of glacioeustatic fluctuations. One response appears at lower-frequency or second-order cycles and is marked by more substantial, nonreversible, taxic change at the Eocene–Oligocene boundary, at the Rupelian–Chattian (Early–Late Oligocene) boundary, and during a Late Oligocene transgressive phase. These faunal changes were responses to climatic changes forced by glaciations signaled by oceanic oxygen-isotope maxima. The second response is seen in fluctuations in the abundances of benthic neritic taxa. Rapid changes in infaunal-to-epifaunal ratios appear to chronicle reversible “short-term” local paleoenvironmental shifts forced by third-order cycles. Sequence stratigraphic packages and bounding surfaces are easier to decipher in sequences characteristic of the warmer and more sluggish Priabonian ocean than in the cooler and better-ventilated Rupelian ocean. The major (second-order) physical event at the Rupelian–Chattian boundary is recorded faunally but shows a relatively muted impact on the regional succession of neritic foraminifera compared to the sequence boundary coinciding with glaciation Oi1 in the very earliest Oligocene. We interpret, from graphic correlation and cluster analysis, that patterns of faunal change reflect endemism that developed on a broad neritic zone with wide variation in intensity of oceanic influence.

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SEPM Special Publication

Micropaleontologic Proxies for Sea-Level Change and Stratigraphic Discontinuities

Hilary Clement Olson
Hilary Clement Olson
Institute for Geophysics, University of Texas, 4412 Spicewood Springs Rd., Bldg. 600, Austin, Texas 78759-8500, U.S.A.
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R. Mark Leckie
R. Mark Leckie
Department of Geosciences, University of Massachusetts, 611 N. Pleasant St., Amherst Massachusetts 01003, U.S.A.
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SEPM Society for Sedimentary Geology
Volume
75
ISBN electronic:
9781565762121
Publication date:
January 01, 2003

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