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GCAGS Transactions

Abstract


Gulf Coast Association of Geological Societies Transactions Vol. 58 (2008), Pages 355-361

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.

Figure 1. Number of highest occurrences (HOs) of Extinction Group species per 0.1 myr in our 21 deep-sea study sites (Hayward et al., 2007) showing earlier withdrawals in deeper water sites. Sites are arranged in order of decreasing depth (left to right).

 

Figure 2. Comparison of the timing of highest occurrences (HOs) of Extinction Group species in ten regions of the world oceans: North Atlantic (Kawagata et al., 2005), South Atlantic (O’Neill et al., 2007), Northwest Atlantic (Hayward et al., 2007), Mediterranean Sea (Hayward et al., 2007), Caribbean Sea (Hayward et al., 2006), North Indian Ocean (Kawagata et al., 2006), Northeast Pacific (Hayward et al., 2007), South China Sea (Kawagata et al., 2007), and Southwest Pacific (Hayward, 2002).

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