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Paleontological Research
Abstract
Abstract.
We studied the deep-sea benthic foraminiferal fauna from core NGC108 (36°36.85′N, 158°20.90′E; 645 cm long, recovered from 3,390 m water depth) collected from the Shatsky Rise in the central northwestern Pacific Ocean, to determine the relationship between benthic foraminifera and paleoproductivity in the transitional zone between the subtropical Kuroshio Extension and the subarctic current over the last 187 kyr. Cassidulina reniforme, Eilohedra levicula, and Epistominella exigua were the most abundant species. The relative abundance of C. reniforme was positively correlated with biogenic opal and organic carbon contents, which are proxies for paleoproductivity. The relative abundance of E. exigua was negatively correlated with biogenic opal and organic carbon contents, and the relative abundance of E. levicula had no correlation with biogenic opal and organic carbon contents. We conclude that C. reniforme and E. exigua are indicative of high and low productivity, respectively. The high relative abundances of C. reniforme reflect high paleoproductivity during glacial periods [oxygen isotope stages (OISs) 6, 3, and 2], indicating a southward advance of the Subarctic Front during global cooling. The high relative abundances of E. exigua reflect low paleoproductivity during the interglacial and postglacial periods (OISs 5 and 1). Faunal changes in the deep-sea benthic foraminifera on the Shatsky Rise suggest a direct response to orbital-scale paleoproductivity changes.
We thank H. Kawahata for providing samples. M. Hata thanks Y. Ujiié and M. Shiba for their encouragement. The samples used in this study were collected during cruise NH95-2 of the Northwest Pacific Carbon Cycle Study (NOPACCS) project consigned to the Kansai Environmental Engineering Center Co. Ltd. (KANSO) by the New Energy and Industrial Technology Development Organization (NEDO). This study was supported by JSPS KAKENHI grant number 26400504.
- Faunal reference list of foraminiferal species in this study (in alphabetical order)
- Brizalina pacifica (Cushman and McCulloch). Bolivina acerosa Cushman var. pacifica Cushman and McCulloch, 1942 , p. 185, pl. 21, figs. 2, 3.
- Cassidulina reniforme Nørvang. Cassidulina crassa d'Orbigny var. reniforme Nørvang, 1945 , p. 41, fig. 6.
- Ehrenbergina trigona Goës. Ehrenbergina serrata Reuss var. trigona Goës, 1896 , p. 49; Ehrenbergina trigona Goës: Jones, 1994 , p. 61, pl. 55, figs. 2–3, 5.
- Eilohedra levicula (Resig). Epistominella levicula Resig, 1958, p. 304, fig. 16; Eilohedra levicula (Resig): Lipps, 1965 , p. 124.
- Epistominella exigua (Brady). Pulvinulina exigua Brady, 1884 , p. 696, pl. 103, figs. 13, 14; Epistominella exigua (Brady): Ujiié, 1990 , p. 32, pl. 14, figs. 1a–c.
- Fontbotia wuellerstorfi (Schwager). Anomalina wuellerstorfi Schwager, 1866 , p. 258, pl. 7, fig. 105; Fontbotina wuellerstorfi (Schwager): Loeblich and Tappan, 1987 , p. 583, pl. 634, figs. 10–12.
- Fursenkoina complanata (Egger). Virgulina schreibersiana Czjzek var. complanata Egger, 1893 , p. 292, pl. 8, figs. 91, 92; Fursenkoina complanata (Egger): Jones, 1994 , p. 56, pl. 52, figs. 1–3.
- Globocassidulina subglobosa (Brady). Cassidulina subglobosa Brady, 1881 ; Globocassidulina subglobosa (Brady): Ujiié, 1990 , p. 39, pl. 21, figs. 4–7.
- Gyroidina lamarckiana (d'Orbigny). Rotalina lamarckiana d'Orbigny, 1839 , p. 131, pl. 2, figs. 13–15; Gyroidina lamarckiana (d'Orbigny): Loeblich and Tappan, 1994 , p. 163, pl. 361, figs. 7–12.
- Oridorsalis umbonatus (Reuss). Rotalia umbonatus Reuss, 1851 , p. 75, pl. 5, fig. 35a–c; Oridorsalis umbonatus (Reuss): Ujiié, 1990 , p. 48, pl. 28, figs. 1–3, 5, 6.
- Pacinonion novozealandicum (Cushman and Edwards): Astrononion novozealandicum Cushman and Edwards, 1937 , p. 35, pl. 3, fig. 18a, b; Pacinonion novozealandicum (Cushman and Edwards): Vella, 1962 , p. 290, pl. 1, figs. 10, 11. Ujiié, 1995 , p. 69, pl. 12, fig. 1.
- Porogavelinella ujiiei Kawagata, 1999 , p. 40, figs. 11-1–7.
- Pullenia quinqueloba (Reuss). Nonionina quinqueloba Reuss, 1851 , p. 71, pl. 5, fig. 31; Pullenia quinqueloba (Reuss): Ujiié, 1990 , p. 43, pl. 23, figs. 5–7; pl. 24, figs. 1–5.
- Triloculina frigida Lagoe, 1977 , p. 120, figs. 6, pl. 1, figs. 12, 17.
- Uvigerina peregrina Cushman, 1923 , p. 166, pl. 42, figs. 7–10. Lamb and Miller, 1984 , p. 6, pl. 8, figs. 1–6; pl. 9, figs. 1–5.
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