PP41B-0639 Clay Minerals in Response to the Mid-Pliocene Global Warmth in Polar Regions (ODP, Site 911, Yermak Plateau, Arctic Ocean and Site 1165,
Yana r.
Lena r. Prydz Bay, Antarctica) b.
Beaufort Gyre Laptev Sea J. Junttila (1, 2), K. Strand (2) ° 60 S AC C Khatanga r. (1) Department of Geosciences, P. O. Box 3000, FIN-90014, University of Oulu, Finland Site 744 Site 738 TPDp (2) Thule Institute, P.O. Box 7300, FIN-90014, University of Oulu, Finland, ([email protected]) Site Di TPDs verg 1165 ence rctic Anta Site 65 r current Franz Josef Land 1167 P ola Nansen Basin Novaya Zemlya elf Ice S h West C. Darnley Prydz Site 1166 Yermak Bay Plateau Mawson Mawson Gyre Introduction Coast Davis Kara Sea Amery Fram 911 Ice Strait Shelf Greenland 23/0 Svalbard 9/37 75 ° E 80 5 Barents Sea The Mid-Pliocene global warmth (MPGW), a period when the global average temperatures were significantly warmer than the 0 400 km present, was possibly caused by higher CO2 levels than today and significantly stronger ocean thermohaline circulation due to drastic EGC WSC climatic changes in the Southern Ocean. In the Northern Hemisphere, MPGW could have been one decisive trigger for the intensification of glaciation at 2.7 Ma. Some recent studies in the East Antarctica have shown that the East Antarctic Ice Sheet (EAIS) Fig. 2. a) Location of the ODP Site 1165 drilled into drift sediments at the continental rise off may have varied from a polythermal, dynamic condition to a predominantly cold stable state as recently as the Pliocene period, Prydz Bay, Antarctica (Modified after Grüzner at al. 2005). b) Generalised map of the present-day including MPGW. This presentation may illuminate the Mid-Pliocene climate conditions of the Arctic Ocean and the dynamics of ocean currents in the Prydz Bay region (modified from Smith et al., 1984; Cooper et al., 2004). ACC = Antarctic Circumpolar Current. Norwegian Current the EAIS based on a clay mineral study. Research of this kind, integrated with other proxies, can provide some indication of how the Earth may respond to the future global warming. Fig. 1. Location of the Site 911on the left (modified afer Ruikka & Strand, 2002) (TPD=Transpolar Drift, EGC=East Greenland Current, Material WSC=West Spitsbergen Current).Source areas of smectite, illite, kaolinite and chlorite in the Arctic Ocean on the right (Washner et al.,1999) The Ocean Drilling Program (ODP) Site 911 was drilled on the Yermak Plateau, Arctic Ocean (Fig. 1) to a depth of 505.8 meters Site 911, Yermak Plateau, Arctic Ocean below the seafloor (mbsf). It contained sediments from the Pliocene to Pleistocene ages. ODP Site 1165 was drilled on the Wild Drift Site 1165, Prydz Bay, Antarctica on the Continental Rise off Prydz Bay, East Antarctica, (Fig. 2) to a total depth of 999.1 mbsf. Of special interest is the sediment column between 0 and 50 mbsf, which consists of a well-preserved section of Pliocene- to Pleistocene-age sediments. 0 8 1.2-1.5 Ma (Diatom, 10 Methods Whitehead & 9 Bohaty, 2003)
20 The X-Ray diffraction (XRD) analysis was performed on oriented clay samples as described by Hardy and Tucker (1988). 10 Diffractograms were recorded by a Siemens D 5000 with copper radiation (40 kV, 40 mA) at angles ranging from 2˚ to 32˚ 2θ (0.02˚ ) ) f f
s 2θ per second) immediately after the treatments of the samples. The principal four clay mineral groups was recognised by their basal 11 30 s b b m m ( ( spacings at 7 Å (kaolinite, chlorite), 10 Å (illite), 12-15 Å (smectite), 14 Å (chlorite). In this study, chlorite (004) was identified at h h t t p
p 12 Pleistocene e e 40 3.54 Å and kaolinite (002) at 3.58 Å, and this proportion was used to calculate the quantities of kaolinite and chlorite from the joint D D peak at 7 Å. MacDiff software version 4.2.5 (http://www.geologie.uni-frankfurt.de/Staff/Homepages/Petschick/RainerE.html)
13 Plio-Pleistocene 50 was used to quantify clay minerals, which were subsequently used to calculate percentages using weighting factors (Biscaye 1965).
Since no internal standards were used, the precise accuracy of this procedure is not known, but the quantitative analyses justify 14 60 interpretations of fluctuations around +/- 2%. 15 70 0.78 Ma Results and conclusions (Polarity, 16 0 20 40 60 80 20 40 60 80 20 40 60 80 20 40 60 80 0 10 20 30 40 50 60 70 80 10 20 30 40 50 60 70 80 10 20 30 40 50 60 70 80 10 20 30 40 50 60 70 80 Myhre et al., 1995) The Pliocene sediments at Site 911 have higher smectite content and lower kaolinite and chlorite contents compared to the Pleistocene % Smectite % Illite % Kaolinite % Chlorite samples (Fig. 3). This may indicate more active sea-ice conditions for smectite transportation from the Kara and Laptev Seas (Fig. 1) % Smectite % Illite % Kaolinite %Chlorite during the Pliocene compared to the Pleistocene sea-ice transportation conditions.This is not surprising if the Kara Sea was frozen to 2.7-3.2 Ma (Diatom, 390 the ground during Pleistocene (cf. Siegert & Dowdeswell, 2004) and the smectite source area (Putorana) was covered with continental 26 2.78 Ma Whitehead & (Nannofossil, ice sheet (cf. Siegert et al. 2001). The Mid-Pliocene sediments at Site 1165 (Fig. 4) show increasing smectite content and decreasing Bohaty, 2003) Sato & Kameo, 1996) illite content and suggest that the EAIS at that time may have been more dynamic than that during the Plio-Pleistocene transition, to 400 which the results were compared (Junttila et al., 2005). 28 ) ) f f s s b References b m m
( 410 (
h h t t p Biscaye, P.F., 1965. Mineralogy and sedimentation of recent deep-sea clay in the Atlantic Ocean Sato, T. & Kameo, K., 1996. Pliocene to Quaternary calcareous nannofossil biostratigraphy of p e e
D 30 and adjacent seas and oceans. Geol. Soc. Am. Bull. 76, 803-832. the Arctic Ocean, with reference to late Pliocene glaciation. In Thiede, J., Myhre, A.M., Firth, D
Cooper, A.K., and O'Brien, P.E., 2004. Leg 188 synthesis: transitions in the glacial history of the J.V., Johnson, G.L., and Ruddiman, W.F. (eds.): Proceedings of the Ocean Drilling Program, Mid-Pliocene 420 Mid-Pliocene Prydz Bay region, East Antarctica, from ODP drilling. In Cooper, A.K., O'Brien, P.E., and Richter, Scientific Results, Vol. 151, 39-59. College Station, Texas, USA. C. (Eds.), Proc. ODP, Sci. Results, 188 [Online]. Available from World Wide Web: http://www- Siegert, M., Dowdeswell, J., Hald, M., Svendsen, J-I., 2001. Modelling the Eurasian Ice Sheet odp.tamu.edu/publications/188_SR/synth/synth.htm. [Cited YYYY-MM-DD] through a full (Weichselian) glacial cycle. Global and Planetary Change, 31, 367-385. Grützner, J., Hillenbrand, C-D., Rebesco, M., 2005. Terrigenous flux and biogenic silica Siegert, M., Dowdeswell, J., 2004. Numerical reconstructions of the Eurasian Ice Sheet and 32 430 deposition at the Antarctic continental rise during the late Miocene to early Pliocene: implications climate during the Late Weichselian. Quaternary Science Reviews, 23, 1273-1283. for ice sheet stability and sea ice coverage. Global and Planetary Change, 45, 131-149 Smith, N., Dong, Z., Kerry, K., and Wright, S., 1984. Water masses and circulation in the region Hardy, R., Tucker, M., 1988. X-ray powder diffraction of sediments. In Tucker, M. (edit.) of Prydz Bay, Antarctica. Deep-Sea Res., 31:1121–1147. Techniques in sedimentology. Blackwell Scientific Publications, Oxford, 191-228. Washner, M., Müller, C., Stein, R., Ivanov, G., Levitan, M., Shelekhova, E. & Tarasov, G., 1999 440 Junttila, J., Ruikka, M., Strand, K., 2005. Clay Mineral Assemblages in High-Resolution Plio- Clay-mineral distribution in surface sediments of the Eurasian Arctic Ocean and cintinental 34 Pleistocene Interval at ODP Site 188-1165, Prydz Bay, Antarctica. Global and Planetary margin as indicator for source areas and transport pathways - a synthesis. Boreas, Vol. 28, pp. 0 20 40 60 80 20 40 60 80 20 40 60 80 20 40 60 80 0 10 20 30 40 50 60 70 80 10 20 30 40 50 60 70 80 10 20 30 40 50 60 70 80 10 20 30 40 50 60 70 80 Change, 45, 151-163. 215-233. Oslo Myhre, A. M., Thiede, J. & Firth, J. V. (eds.), 1995: Proceedins of the Ocean Drilling Program, Whitehead, J.M., Bohaty, S.M., 2003. Data report: Quaternary-Pliocene diatom biostratigraphy % Smectite % Illite % Kaolinite % Chlorite Scientific Results, Vol. 151. College Station, Texas, U.S.A. of ODP Sites 1165 and 1166, Cooperation Sea and Prydz Bay. In Cooper, A.K., O'Brien, P.E., % Smectite % Illite % Kaolinite %Chlorite Ruikka, M., & Strand, K., 2002. Clay minerals in response to the Pleistocene climate change on and Richter, C. (Eds.), Proc. ODP, Sci. Results, 188 [Online].Available from World Wide Web: Fig. 3. Clay mineral distribution at Site 911. the Yermak Plateau, Arctic Ocean (ODP, Site 911). Polar Record 38 (206): 241-248.