Quaternary Calcareous Nannofossil Datums and Biochronology in the North Atlantic Ocean, IODP Site U13081 Tokiyuki Sato,2 Shun Chiyonobu,3 and David A

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Channell, J.E.T., Kanamatsu, T., Sato, T., Stein, R., Alvarez Zarikian, C.A., Malone, M.J., and the Expedition 303/306 Scientists Proceedings of the Integrated Ocean Drilling Program, Volume 303/306

Data report: Quaternary calcareous nannofossil datums and biochronology in the North Atlantic Ocean, IODP Site U13081 Tokiyuki Sato,2 Shun Chiyonobu,3 and David A. Hodell4

Chapter contents Abstract

Abstract ...... 1 We studied high-resolution Quaternary calcareous nannofossil Introduction ...... 1 biostratigraphy to clarify the relationship between nannofossil events and oxygen isotope stratigraphy using the continuous sed- Samples and methods...... 1 iment sequence from Integrated Ocean Drilling Program Site Results ...... 2 U1308 in the North Atlantic Ocean. Results indicate that some Remarks on stratigraphic position of datums . 2 nannofossil events found in the section, such as the last occur- Conclusion ...... 3 rences of Reticulofenestra asanoi and Gephyrocapsa spp. (large), are Acknowledgments...... 3 located in a different stratigraphic position compared to previous References ...... 3 studies. We also clarify the critical stratigraphic positions of both Figures ...... 5 the first occurrence of Emiliania huxleyi and the last occurrence of Table ...... 9 Pseudoemiliania lacunosa, which occur just below the highest peaks of each marine isotope Stage 8 and 12.

Introduction Quaternary calcareous nannofossil datums and their chronostratigraphic framework have been discussed over the last 20 y mainly based on their correlation to magnetostratigraphy (Raffi and Rio, 1979; Rio, 1982; Takayama and Sato, 1987) or to oxygen isotope stages (Thierstein et al., 1977; Wei, 1993; Raffi et al., 1993; Raffi, 2002). These studies indicate that Quaternary nannofossil datums show a small diachroneity between different latitudes. However, some studied sections were not completely continuous because of coring problems or were not suitable for high-resolution study be- 1 Sato, T., Chinyonobu, S., and Hodell, D.A., 2009. cause of low sedimentation rate. Data report: Quaternary calcareous nannofossil datums and biochronology in the North Atlantic In 2005, drilling sites of Integrated Ocean Drilling Program Ocean, IODP Site U1308. In Channell, J.E.T., (IODP) Expedition 303 in the North Atlantic Ocean were chosen Kanamatsu, T., Sato, T., Stein, R., Alvarez Zarikian, to recover cores that would yield complete and continuous re- C.A., Malone, M.J., and the Expedition 303/306 cords of millennial-scale environmental variability. This means Scientists, Proc. IODP, 303/306: College Station, TX that the core samples from Expedition 303 are suitable for study (Integrated Ocean Drilling Program Management International, Inc.). of millennial climate variability throughout the Quaternary. The doi:10.2204/iodp.proc.303306.210.2009 main purpose of this study is to clarify the detailed relationship 2 Institute of Applied Earth Sciences, Faculty of between Quaternary nannofossil events and oxygen isotope stra- Engineering and Resource Science, Akita tigraphy using the continuous Quaternary sedimentary sequence University, 1-1 Tegata-gakuencho, Akita 010-8502, from Site U1308 in the North Atlantic Ocean (Fig. F1). Japan. [email protected] 3 Institute of Geology and Paleontology, Graduate School of Science, Tohoku University, Aramaki- Aoba, Sendai 980-8578, Japan. Samples and methods 4 Department of Geological Sciences, University of Florida, 214 Williams Hall, PO Box 112120, Although core catcher samples were used for lower Quaternary Gainesville FL 32611, USA. samples below the Cobb Mountain Subchron, samples above the

Proc. IODP | Volume 303/306 doi:10.2204/iodp.proc.303306.210.2009 T. Sato et al. Data report: nannofossil datums and biochronology

Cobb Mountain Subchron were collected at ~5 cm ama Chron. Datum 13 is detected just below the intervals from the upper Quaternary sequences for Olduvai Subchron (Fig. F2). discussion of the relationship between oxygen iso- We also compared the nannofossil datum events tope stratigraphy and nannofossil datums. The with oxygen isotope stratigraphy (Fig. F2). Datums 2 depth of each sample is calculated to meters compos- and 3 are respectively situated in marine isotope ite depth (mcd) based on core to core correlation. As Stage (MIS) 8 and 12. Both datums are situated just the Quaternary sedimentation rate of this site is 7.6 before the highest peak of the respective MIS. Da- cm/k.y. (Channell et al., 2006), the studied intervals tums 5 and 6 are respectively found in MIS 21 and (~5 cm) correspond to 650 y. Samples were prepared 27, and Datums 7, 8, 9, and 10 are found in MIS 34, by smear slide methods and were studied under a 35, 38, and 44, respectively. Ages of nannofossil da- Zeiss Axio Imager polarizing microscope under tums and the relationship between nannofossil bio- 1600× magnification. stratigraphy, magnetostratigraphy, and oxygen isotope stratigraphy are summarized in Figure F3 and Results Table T1. A total of 11 uppermost Pliocene to Quaternary nannofossil datums are detected in the Site U1308 sec- Remarks on stratigraphic tion (Table T1; Figs. F2, F3). Based on the datum position of datums numbers of Sato and Takayama (1992), Datum 2, the first occurrence of Emiliania huxleyi, which defines Takayama and Sato (1987) identified 11 Quaternary the Zone NN20/NN21 boundary of Martini’s zona- nannofossil datums at Deep Sea Drilling Project Sites tion, is found at 16.88–16.93 mcd. Datum 3, the last 606, 607, 608, 609, 610, and 611, located between occurrence of Pseudoemiliania lacunosa, which corre- 37°N and 53°N in the North Atlantic Ocean. They lates to the Zone NN19/NN20 boundary, is detected described that 9 of 11 Quaternary nannofossil da- between 28.14 and 28.19 mcd. Because Helicosphaera tums were traceable to all sites in the North Atlantic inversa occurs rarely throughout the section, Datums Ocean and that the stratigraphic positional relation- 1 and 4 were not recognized here. Datums 5 and 7, ship of each nannofossil datum to magnetostratigra- the last and first occurrences of Reticulofenestra phy were invariable. Site U1308 is a reoccupation of asanoi, are respectively found at 55.47–55.52 and Site 609. 80.28–80.33 mcd. Datums 6 and 8, the first occur- Site U1308 is suitable for high-resolution study to rence of Gephyrocapsa parallela and last occurrence of clarify the relationship between magnetostratigra- the large form Gephyrocapsa spp., are situated at phy, oxygen isotope stratigraphy, and calcareous 66.40–66.45 and 84.56–84.86 mcd, respectively. Da- nannofossil biostratigraphy in detail (Figs. F2, F3). tums 9 (last occurrence of Helicosphaera sellii; 84.86– The relationship between magnetostratigraphy, oxy- 90.16 mcd), 10 (first occurrence of large Gephyro- gen isotope stratigraphy, and calcareous nannofossil capsa spp.; 100.59–103.52 mcd), 11 (first occurrence biostratigraphy has been previously discussed based of Gephyrocapsa oceanica; 123.07–131.27 mcd), 12 on study of deep-sea sediments (Thierstein et al., (first occurrence of Gephyrocapsa caribbeanica; 1977; Wei, 1993; Raffi et al., 1993; Raffi, 2002). Raffi 131.27–132.74 mcd), and 13 (last occurrence of Dis- (2002) and Raffi et al. (2006) summarized the bio- coaster brouweri; 114.51–153.29 mcd) are situated in chronology of nannofossil events and discussed the the uppermost Pliocene to lower Pleistocene inter- synchroneity of nannofossil datum events. val. Although our results are almost the same as those by Based on the stratigraphic position of these datums Raffi et al. (2006), some datums such as Datums 5 at Site U1308, we also correlate the datums to mag- and 8 are biochronostratigraphically different from netostratigraphy, which was studied by Channell et those described by Raffi et al. (2006). al. (2006) (Fig. F2). Both Datums 2 and 3 are traceable to the Brunhes Chron. Datum 5 is situated be- Datum 8: last occurrence of Gephyrocapsa tween the Brunhes Chron and Jaramillo Subchron of the Matuyama Chron, and Datum 6 is traceable to spp. (large) the top of the Jaramillo Subchron. Datum 7 is found Gephyrocapsa spp. (large) in this study is correlated to between the Jaramillo and Cobb Mountain Sub- large Gephyrocapsa spp. by Raffi (2002) and Raffi et chrons, and Datum 8 is situated within the Cobb al. (2006) and Gephyrocapsa spp. A-B by Wei (1993). Mountain Subchron of the Matuyama Chron (Fig. Raffi (2002) correlated the position of Datum 8 to F2). Datums 9–12 are present between the Cobb MIS 37–38 below the Cobb Mountain Subchron. Our Mountain and the Olduvai Subchrons in the Matuy- results, however, indicate that Datum 8 is found

Proc. IODP | Volume 303/306 2 T. Sato et al. Data report: nannofossil datums and biochronology within the Cobb Mountain Subchron at Site U1308 tion just before the highest peak of MIS 8 and 12, re- and is correlated to MIS 35. This correlates well with spectively. results from Sites 609, 610, and 611 (Takayama and Sato, 1987) and from Quaternary sequences in Japan (Sato and Takayama, 1992). Acknowledgments Samples for this study were provided by the Inte- Datum 5: last occurrence of Reticulofenestra grated Ocean Drilling Program. We are grateful to asanoi many scientific staff on board the JOIDES Resolution. Although the stratigraphic position of Datum 5, last occurrence of R. asanoi at Site U1308, is correlated to the lowest peak of MIS 21 in this study, its position References by Wei (1993) and Raffi (2002) is traced to MIS 22. Channell, J.E.T., Sato, T., Kanamatsu, T., Stein, R., Malone, Raffi (2002) summarized the biochronological prob- M., Alvarez-Zarikian, C., and the IODP Expeditions 303 lems introduced by the influence of regional envi- and 306 Scientists, 2006. IODP Expeditions 303 and 306 ronmental conditions on diachronous placement of monitor Miocene-Quaternary climate in the North biological datum events. However, Datum 5 was in- Atlantic. Sci. Drill., 2:4–10. doi:10.2204/ terpreted as being abrupt and consistently isochro- iodp.sd.2.01.2006 nous and is associated with the mid-Pleistocene rev- Raffi, I., 2002. Revision of the early-middle Pleistocene cal- olution (Raffi, 2002). Our results indicate that the careous nannofossil biochronology (1.75–0.85 Ma). presence of a small difference in chronostratigraphic Mar. Micropaleontol., 45(1):25–55. doi:10.1016/S0377- position of this datum may reflect the influence of 8398(01)00044-5 regional environmental conditions. Raffi, I., Backman, J., Fornaciari, E., Pälike, H., Rio, D., Lou- rens, L., and Hilgen, F., 2006. A review of calcareous Datums 2 and 3: first occurrence nannofossil astrobiochronology encompassing the past 25 million years. Quat. Sci. Rev., 25(23–24):3113–3137. of Emiliania huxleyi and last occurrence doi:10.1016/j.quascirev.2006.07.007 of Pseudoemiliania lacunosa Raffi, I., Backman, J., Rio, D., and Shackleton, N.J., 1993. Datums 2 and 3 in this study occur in MIS 8 and 12, Plio–Pleistocene nannofossil biostratigraphy and cali- respectively. These results are the same as those of bration to oxygen isotope stratigraphies from Deep Sea Drilling Project Site 607 and Ocean Drilling Program Thierstein et al. (1977), Wei (1993), and Raffi (2002). Site 677. Paleoceanography, 8(3):387–408. doi:10.1029/ Furthermore, our high-resolution study also clarifies 93PA00755 the critical stratigraphic positions of both datums, Raffi, I., and Rio, D., 1979. Calcareous nannofossil bio- which are situated just before the highest peaks of stratigraphy of DSDP Site 132—Leg 13 (Tyrrhenian Sea- each MIS (Fig. F2). Datum 2 is at 16.88–16.93 mcd, Western Mediterranean). Riv. Ital. Paleontol. Stratigr., 0.82 m below the highest peak of MIS 8. Datum 3 is 85:127–172. also traceable to 28.14–28.19 mcd, 0.41 m below the Rio, D., 1982. The fossil distribution of coccolithophore highest peak of MIS 12. These differences between genus Gephyrocapsa Kamptner and related Plio–Pleisto- MIS peak and datum level are calculated as 12.6 k.y. cene chronostratigraphic problems. In Prell, W.L., Gard- (Datum 2) and 16.2 k.y. (Datum 3) (Fig. F4). ner, J.V., et al., Init. Repts. DSDP, 68: Washington, DC (U.S. Govt. Printing Office), 325–343. doi:10.2973/ dsdp.proc.68.109.1982 Conclusion Sato, T., and Takayama, T., 1992. A stratigraphically signifi- We clarify the critical relationship between nanno- cant new species, Reticulofenestra asanoi (calcareous nannofossil). In Ishizaki, K., and Saito, T. (Eds.), Centenary of fossil biostratigraphy, oxygen isotope stratigraphy Japanese Micropaleontology: Tokyo (Terra Sci. Publ.), 457– and magnetostratigraphy based on high-resolution 460. http://www.terrapub.co.jp/e-library/cjm/pdf/ studies of the Quaternary sequence of Site U1308 in 0457.pdf the North Atlantic Ocean. The last occurrence of Ge- Takayama, T., and Sato, T., 1987. Coccolith biostratigraphy phyrocapsa spp. (large) is situated within the Cobb of the North Atlantic Ocean, Deep Sea Drilling Project Mountain Subchron, the same as results by Ta- Leg 94. In Ruddiman, W.F., Kidd, R.B., Thomas, E., et al., kayama and Sato (1987), and is traceable to MIS 35. Init. Repts. DSDP, 94: Washington, DC (U.S. Govt. Print- The first occurrence of E. huxleyi and last occurrence ing Office), 651–702. doi:10.2973/ of P. l acu n osa are correlated to the stratigraphic posi- dsdp.proc.94.113.1987

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Thierstein, H.R., Geitzenauer, K.R., Molfino, B., and Shack- phy. Paleoceanography, 8(1):85–99. doi:10.1029/ leton, N.J., 1977. Global synchroneity of late Quater- 92PA02504 nary coccolith datum levels validation by oxygen isotopes. Geology, 5(7):400–404. doi:10.1130/ Initial receipt: 29 September 2008 0091-7613(1977)5<400:GSOLQC>2.0.CO;2 Acceptance: 10 September 2009 Wei, W., 1993. Calibration of upper Pliocene–lower Pleisto- Publication: 25 November 2009 cene nannofossil events with oxygen isotope stratigra- MS 303306-210

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Figure F1. Location map of Site U1308 analyzed in this study. Arrows indicate major deepwater flows. DSOW = Denmark Strait Overflow Water, NGS = Norwegian Greenland Sea, ISOW = Iceland Sea Overflow Water, WTRO = Wyville Thomson Ridge Overflow, GFZ = Charlie Gibbs Fracture Zone, LSW = Labrador Sea Water, LDW = Lower Deep Water.

70° N Sill depths: WTRO 650 m NGS ISOW 400 m DSOW 600 m GFZ ~3650 m DSOW

ISOW Site 984

60° Site Site 983 LSW U1307 Site WTRO Site 982 Site U1306 U1305 Sites Site 980/981 552 Rockall Site Trough U1304

50° Sites U1302/ Sites U1303 609/U1308 LDW

Site NADW 607 40°

60°W 40° 20° 0°

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Figure F2. Stratigraphic distributions of marker species of each datum found at Site U1308. Circled numbers = stratigraphic boundaries of magnetic polarity and positions of each datum. PDB = Peedee belemnite, J = Jara- millo, CM = Cobb Mountain, O = Olduvai. FO = first occurrence, LO = last occurrence.

δ18O (‰ PDB) 4.5 3.5 2.5 5 4 3 2 Polarity +2.0+3.0+4.0+5.0 Chron 0 0 1 0 1 Nannofossil datums (Sato and Takayama, 1992)

5 7 88 7

20 2 FO Emiliania huxleyi 20 9 10 9 16.88/16.93 mcd 10 11 12 11 12 28.14/28.19 3 LO Pseudoemiliania lacunosa 13 Brunhes 15 40 15 40

17 19 50 19 49.8±0.4 mcd 55.47/55.52 21

22 5 LO Reticulofenestra asanoi 22 21 23 60 60 24 23 24 25 26

27 25 26 27

28 6 FO Gephyrocapsa parallela 65.7±0.4 66.40/66.45 28 29

30 J 30 29 31 72.0±0.7 33 80 80 33 FO Reticulofenestra asanoi Depth (mcd) 7

35 80.28/80.33 35 84.56/84.86 CM 84.5±1.0 8 LO large Gephyrocapsa spp.

37 84.86/90.16

39 37 39 9 LO Helicosphaera sellii 41 43 100

43 100

100 45 10 FO large Gephyrocapsa spp. 45 100.59/103.52 47 49 120 120 Matuyama

11 FO Gephyrocapsa oceanica 123.07/131.27 131.27/132.74 12 FO Gephyrocapsa caribbeanica 133.5±0.7

147.0±1.0 144.51/153.29 150 13 LO Discoaster brouweri

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Figure F3. Summary of calcareous nannofossil datum events versus time interval from 0 to 2.0 Ma, Site U1308. PDB = Peedee belemnite, J = Jaramillo, CM = Cobb Mountain, O = Olduvai. FO = first occurrence, LO = last occurrence.

Benthic δ18O 4.5 4 3.5 (‰5 PDB) 0 Polarity Chron +5.0 +4.0 +3.0 +2.0 0 1 100 200 5 Nannofossil datums

300 (Sato and Takayama, 1992) Age 200 7 400 2 FO Emiliania huxleyi 265 ka

9 500 600

400 11 Brunhes 700 3 LO Pseudoemiliania lacunosa 451 ka 13 800 900 600 15 1000

17 1100

19 1200 800

1300 5 LO Reticulofenestra asanoi 853 ka 21 23 1400 25

1000 27 1500 6 FO Gephyrocapsa parallela 987 ka 29 J Age (ka) 31 1600 33 7 FO Reticulofenestra asanoi 1128 ka CM 35 8 LO large Gephyrocapsa spp. 1182 ka 1200 37 9 LO Helicosphaera sellii 1219 ka 39 41 43 10 FO large Gephyrocapsa spp. 1392 ka 1400 45

Matuyama 49

1600

11 FO Gephyrocapsa oceanica 1706 ka

12 FO Gephyrocapsa caribbeanica 1763 ka 1800

2000 13 LO Discoaster brouweri 1990 ka

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Figure F4. Relationship between stratigraphic position of nannofossil Datums 2 (first occurrence of Emiliania huxleyi) and 3 (last occurrence of Pseudoemiliania lacunosa) and oxygen isotope stratigraphy, Site U1308. PDB = Peedee belemnite, MIS = marine isotope stage.

2 Bottom: Emiliana huxleyi 3 Top : Pseudoemiliania lacunosa 264.6–265.47 ka 450.61–452.20 ka 2.5

3.5 O (‰ PDB) 18 δ

4.5

252.43 ka (MIS 8) 435.24 ka (MIS 12) 5 0 100 200 300 400 500 600 Age (ka)

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Table T1. Calcareous nannofossil datum stratigraphic positions and ages, Site U1308. (See table notes.)

Site U1308 Datum Depth Age Age number Calcareous nannofossil datum (mcd) (ka) MIS Chron/Subchron (ka)

2FO Emiliania huxleyi 16.88–16.93 264.64–265.47 8 Brunhes 265 3LO Pseudoemiliania lacunosa 28.14–28.19 450.61–452.20 12 Brunhes 451 5LO Reticulofenestra asanoi 55.47–55.52 852.42–854.05 21 Brunhes~Jaramillo 853 6FO Gephyrocapsa parallela 66.40–66.45 987.34–987.98 27 Top Jaramillo 987 7FO Reticulofenestra asanoi 80.28–80.33 1128.3–1128.7 34 Jaramillo~Cobb Mountain 1128 8LO Gephyrocapsa spp. (large) 84.56–84.86 1180.5–1184.3 35 In Cobb Mountain 1182 9LO Helicosphaera sellii 84.86–90.16 1184.3–1255.2 38 Cobb Mountain~Olduvai 1219 10 FO Gephyrocapsa spp. (large) 100.59–103.52 1371.3–1412.8 44 Cobb Mountain~Olduvai 1392 11 FO Gephyrocapsa oceanica 123.07–131.27 — — Above Olduvai 1706* 12 FO Gephyrocapsa caribbeanica 131.27–132.74 — — Above Olduvai 1763* 13 LO Discoaster brouweri 144.51–153.29 — — Below Olduvai 1990*

Notes: Datum numbers by Sato and Takayama (1992). MIS = marine isotope stage. FO = first occurrence, LO = last occurrence, — = no data, * = based on magnetostratigraphy.

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