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The AAPG/Datapages Combined Publications Database
GCAGS Transactions
Abstract
EXTENDED ABSTRACT: The Last Global Extinction in the Deep Sea
Bruce W. Hayward1, Shungo Kawagata2,
Hugh R. Grenfell1, Ashwaq T. Sabaa1, and Tanya O’Neill3
1Geomarine Research, 49 Swainston Rd., St. Johns, Auckland, New Zealand
2Yokohama National University, 79-2 Tokiwadai, Hodogaya-ku, Yokohama, 240-8501, Japan
3Department of Earth Science, Massey University, Priv. Bag 11222, Palmerston North, New Zealand
EXTENDED ABSTRACT
The disappearance of a small group of elongate, cylindrical, deep-sea benthic
foraminifera
close to the Brunhes/Matuyama boundary (Early-Middle Pleistocene boundary)
was first noted less than 30 years ago (Lutze, 1979; Caralp, 1985). Its potential
biostratigraphic
value was immediately recognised, as the Pleistocene is a period with few
useful foraminiferal events to assist dating. The disappearance was found to
occur
throughout the Atlantic by Weinholz and Lutze (1989) who dubbed it the “Stilostomella
Extinction.” It was extended to a global extinction by Schönfeld
(1996) who summarized
known records worldwide and concluded that it was diachronous and involved
species of
at least five genera.
Over the last six years, we have documented this period of enhanced extinction
more extensively (Hayward, 2001, 2002; Hayward et al., 2006; 2007; Kawagata
et al.,
2005, 2006, 2007; O’Neill et al., 2007), and now conclude that about
twenty percent (19
genera, 95 species) of cosmopolitan, deep-sea (500-4000 m [1640-13,123 ft]),
benthic
foraminiferal
species became extinct during the late Pliocene – Middle Pleistocene
(3-0.12
Ma) (Fig. 1). A peak period of extinctions (76 species) occurred during the
mid-
Pleistocene Climate Transition (MPT, 1.2-0.55 Ma) (Fig. 2). One whole family
(Stilostomellidae, 30 species) was wiped out and a second (Pleurostomellidae,
29 species)
was decimated with just one species possibly surviving through to the present.
These
two families plus 10 genera in the Nodosariidae are here referred to as the
Extinction
Group (Table 1). All members of the Extinction Group had become extinct by
the end of
the MPT, except for two species (Proxifrons advena, and Pleurostomella alternans)
that
appear to have survived through to the present, and four others (Pleurostomella
[3 species],
and Neugeborina longiscata) that finally died out in the late Middle Pleistocene
(0.4-0.2 Ma).
Extinction Architecture and Possible Cause
Our studies at 21 deep sea core sites world-wide show widespread pulsed declines in abundance and diversity of the Extinction Group species during more extreme glacial periods, with partial interglacial recoveries. These declines started in the late Pliocene in southern-sourced deep-water masses (Antarctic Bottom Water, and Circum-Polar Deep Water) and extending into intermediate waters (Antarctic Intermediate Water, and North Atlantic Deep Water) in the MPT, with the youngest declines in sites furthest downstream from high-latitude intermediate water source areas.
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