Causes and consequences of a middle Pleistocene origin of the modern planktonic foraminifer Neogloboquadrina pachyderma sinistral

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doi: 10.1130/0091-7613(2002)030<0539:CACOAM>2.0.CO;2
Author(s): Kucera, Michal; Kennett, James P.
Author Affiliation(s): Primary:
Royal Holloway University of London, Department of Geology, Egham, United Kingdom
University of California at Santa Barbara, United States
Volume Title: Geology (Boulder)
Source: Geology (Boulder), 30(6), p.539-542. Publisher: Geological Society of America (GSA), Boulder, CO, United States. ISSN: 0091-7613 CODEN: GLGYBA
Note: In English. 24 refs.; illus.
Summary: Switches in coiling direction of shells of the planktonic foraminifer Neogloboquadrina pachyderma have been extensively used as a paleotemperature proxy from the late Miocene through the Quaternary, exploiting the specific modern polar affinity of the sinistrally coiled form. Here we have reexamined the origin of the modern sinistral form in Pliocene and Pleistocene sediments from Ocean Drilling Program Site 1014 in the eastern North Pacific. By using morphometric and stable isotope data, we show that Pliocene and Pleistocene sinistral forms of N. pachyderma are morphologically and ecologically different and that modern-type sinistral form first appeared ca. 1 Ma. These findings suggest that N. pachyderma sinistral should not be used for calibrated paleoceanographic reconstructions prior to the middle Pleistocene and reinforce the need to assess the origin of specific ecological affinities of other modern planktonic foraminifer species. The first appearance of the modern form and the subsequent evolution of its mean shell size appear to have been synchronous in the North Pacific and the North Atlantic. Such hemispheric evolutionary synchronicity implies existence of trans-Arctic gene flow. The modern-type shell morphology and the specific cold-water affinity of N. pachyderma sinistral may have evolved in response to the onset of the 100 k.y. climate regime in the middle Pleistocene.
Year of Publication: 2002
Research Program: ODP Ocean Drilling Program
Key Words: 10 Paleontology, Invertebrate; 24 Surficial Geology, Quaternary Geology; Affinities; Biochemistry; Biologic evolution; C-13/C-12; Carbon; Cenozoic; Coiling; East Pacific; Foraminifera; Globigerina; Globigerina bulloides; Globigerinacea; Globigerinidae; Invertebrata; Isotope ratios; Isotopes; Leg 167; Marine sediments; Microfossils; Middle Pleistocene; Modern; Morphology; Morphometry; Neogene; Neogloboquadrina; Neogloboquadrina pachyderma; North Pacific; Northeast Pacific; O-18/O-16; ODP Site 1014; Ocean Drilling Program; Oxygen; Pacific Ocean; Paleo-oceanography; Paleoclimatology; Paleoecology; Planktonic taxa; Pleistocene; Pliocene; Protista; Quaternary; Rotaliina; Sediments; Shells; Size; Stable isotopes; Tertiary
Coordinates: N325002 N325002 W1195853 W1195853
Record ID: 2002043016
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