**5. Acknowledgement**

The present study was supported by the Sasagawa Scientific Research grant No.23-601 from the Japan Science Society; the Sumitomo Foundation grant No.103359; awards from the 21st Century COE and the Global COE programs at Nagoya Univ. of the Ministry of Education, Culture, Sports, Science and Technology, Japan (Dynamics of the Sun-Earth-Life Interactive System, No. G-4; From Earth System Science to Basic and Clinical Environmental Studies, No. K-04).

#### **6. References**


Baikal, the dissolved and detrital uranium in the water column are derived mainly from uranium-bearing rocks in the Selenga drainage basin, and are transported to the lake via the Selenga River and its tributaries (Edgington et al., 1996, 1997). Most of this uranium is in a dissolved form. Uranium contained in the sediment is mainly preserved as an authigenic component from dissolved uranium adsorbed on the surface of suspended sediment loads in the river and lake water and diatom frustules produced in the lake, which accumulates on the lake bottom (Edgington et al., 1996, 1997; Goldberg et al., 2010; Sakaguchi et al., 2006). Therefore, there is a possibility that the uranium deposition may be affected by the supply

On the other hand, chronological studies on the bottom sediment in Lake Baikal indicate that the depositional rates are nearly constant through the glacial-interglacial periods over the whole lake area: 14.8 cm/kyr for the last 264 kyr at the Buguldeika saddle (Colman et al., 1999) and 3.9 cm/kyr for the last 6.7 Ma at the underwater Academician Ridge (Kravchinsky et al., 2003). The observed sedimentary features of Lake Baikal suggest that the amount of materials on which the uranium adsorbed would vary little over the entire sequence, and the concentration of uranium in the bottom sediment would be only slightly dependent on the abundances of detritus materials and diatom frustules. Therefore, we believe that the uranium variation strongly influences the input of uranium into the lake, reflecting the weathering in the Selenga drainage basin which was associated with changes in moisture levels in the region.

Comparing the bioSi and uranium variations, the Lake Baikal records from the Buguldeika saddle and the paleoproxy records of global climate change showed only slight differences on glacial-interglacial and centennial-to-millennial scales — there are statistically no significant differences between these two records. Thus, we conclude that the bioSi and uranium records of Lake Baikal sediment follow the same degree of global climate changes

The present study was supported by the Sasagawa Scientific Research grant No.23-601 from the Japan Science Society; the Sumitomo Foundation grant No.103359; awards from the 21st Century COE and the Global COE programs at Nagoya Univ. of the Ministry of Education, Culture, Sports, Science and Technology, Japan (Dynamics of the Sun-Earth-Life Interactive System, No. G-4; From Earth System Science to Basic and Clinical Environmental Studies,

BDP-93 Baikal Drilling Project Members (1997). Preliminary results of the first scientific

Bond, G.; Kromer, B.; Beer, J.; Muscheler, R.; Evans, M. N.; Showers, W.; Hoffmann, S.; Lotti-

*International*, Vol.37, (June 1998), pp. 3-17, ISSN 1040-6182

Drilling on Lake Baikal, Buguldeika site, southeastern Siberia. *Quaternary* 

Bond, R.; Hajdas, I. & Bonani, G. (2001). Persistent solar influence on North Atlantic climate during the Holocene. *Science*, Vol.294, No.5549, (December 2001), pp. 2130-

of detritus materials and the production rate of diatoms.

on time scales covering centuries to tens of millennia.

**4. Conclusion** 

**5. Acknowledgement** 

No. K-04).

**6. References** 

2136, ISSN 0036-8075


Response of Biogenic Silica Production in Lake Baikal and

0012-8252

2190, ISNN 0148-0227

Uranium Weathering Intensity in the Catchment Area to Global Climate Changes 135

Mackay, A. W. (2007). The paleoclimatology of Lake Baikal: A diatom synthesis and

Manabe, S. & Broccoli, A. J. (1985). The influence of continental ice sheets on the climate of

Murakami, T.; Katsuta, N.; Yamamoto, K.; Takamatsu, N.; Takano, M.; Oda, T.; Matsumoto, G.

*of Paleolimnology*, Vol.43, No.2, (February 2010), pp. 369-383, ISSN 0921-2728 Murakami, T.; Takamatsu, T.; Katsuta, N.; Takano, M.; Yamamoto, K.; Nakamura, T. and

Petit, J. R.; Jouzel, J.; Raynaud, D.; Barkov, N. I.; Barnola, J. M.; Basile, I.; Bender, M.;

Antarctica. *Nature*, Vol.399, No.6735, (June 1999), pp. 429-436, ISSN 0023-0836 Prokopenko, A. A.; Hinnov, L. A.; Williams, D. F. & Kuzmin, M. I. (2006). Orbital forcing of

Prokopenko, A. A.; Karabanov, E. B.; Williams, D. F.; Kuzmin, M. I.; Shackleton, N. J.;

*Quaternary Research*, Vol.55, No.2, (March 2001), pp. 123-132, ISSN 0033-5894 Prokopenko, A. A.; Williams, D. F.; Karabanov, E. B. & Khursevich, G. K. (1999). Response

Prokopenko, A. A.; Williams, D. F.; Karabanov, E. B. & Khursevich, G. K. (2001b).

Prokopenko, A. A.; Williams, D. F.; Kuzmin, M. I.; Karabanov, E. B.; Khursevich, G. K. &

Nos. 23-24, (December 2006), pp. 3431-3457, ISSN 0027-3791

in the sediment of Lake Baikal, southeast Siberia.

(October 1999), pp. 239-253, ISSN 0012-821X

pp. 217-226, ISSN 0921-8181

8222

prospectus. *Earth-Science Review*, Vol.82, No.3-4, (June 2007), pp. 181-215, ISSN

ice age. *Journal of Geophysical Research*, Vol.90, No.D1, (February 1985), pp. 2167-

I.; Horiuchi, K. & Kawai, T. (2010) A 27-kyr record of environmental change in central Asia inferred from the sediment record of Lake Hovsgol, northwest Mongolia. *Journal* 

Kawai, T. (under review) Centennial- to millennial-scale climate shifts in continental interior Asia repeated between warm-dry and cool-wet conditions during the last three interglacial states: Evidence from uranium and biogenic silica

Chappellaz, J.; Davis, J.; Delaygue, G.; Delmotte, M.; Kotlyakov, V. M.; Legrand, M.; Lipenkov, V.; Lorius, C.; Pépin, L.; Ritz, C.; Saltzman, E. & Stievenard, M. (1999). Climate and Atmospheric History of the Past 420,000 years from the Vostok Ice Core,

continental climate during the Pleistocene: a complete astronomically tuned climatic record from Lake Baikal, SE Siberia. *Quaternary Science Reviews*, Vol.25,

Crowhurst, S. J.; Peck, J. A.; Gvozdkov, A. N. & King, J. W. (2001a). Biogenic silica record of the Lake Baikal response to climatic forcing during the Brunhes.

of Lake Baikal ecosystem to climate forcing and *p*CO2 change over the last glacial/interglacial transition. *Earth and Planetary Science Letters*, Vol.172, Nos.3-4,

Continental response to Heinrich events and Bond cycles in sedimentray record of Lake Baikal, Siberia. *Global and Planetary Change*, Vol.28, No.1-4, (February 2001),

Peck, J. A. (2002). Muted climate variations in continental Siberia during the mid-Pleistocene epoch. *Nature*, Vol.418, No.6893, (July 2002), pp. 65-68, ISSN 0023-0836 Reimer, P. J.; Baillie, M. G. L.; Bard, E.; Bayliss, A.; Beck, J. W.; Bertrand, C. J. H.; Blackwell,

P. G.; Buck, C. E.; Burr, G. S.; Cutler, K. B.; Damon, P. E.; Edwards, R. L.; Fairbanks, R. G.; Friedrich, M.; McCormac, G.; Manning, S.; Ramsey, C. B.; Reimer, R. W.; Remmele, S.; Southon, J. R.; Stuiver, M.; Talamo, S.; Taylor, F. W.; van der Plicht, J. & Weyhenmeyer, C. E. (2004). IntCal04 terrestrial radiocarbon age calibration, 0–26 cal kyr BP. *Radiocarbon*, Vol.46, No.3, (December 2004), pp. 1029-1058, ISSN 0033-


EPICA community members (2004). Eight glacial cycles from an Antarctic ice core. *Nature*,

Gavshin, V. M.; Bobrov, V. A. & Khlystov, O. M. (2001). Periodicity in diatom sedimentation

Goldberg, E. L.; Chebykin, E. P.; Zhuchenko, N. A.; Vorobyeva, S. S.; Stepanova, O. G.;

Goldberg, E. L.; Grachev, M. A.; Chebykin, E. P.; Phedorin, M. A.; Kalugin, I. A.; Khlystov,

Imbrie, J.; Hays, J. D.; Martinson, D. G.; McIntyre, A.; Mix, A. C.; Morley, J. J.; Pisias, N. G.;

269-305, Plenum Reidel, ISBN 978-9027717917, Dordrecht, Netherlands Karavanov, E. B.; Prokopenko A. A.; Williams, D. F. and Colman, S. M. (1998) Evidence from

Karabanov, E.; Williams, D.; Kuzumin, M.; Sideleva, V.; Khursevich, G.; Prokopenko, A.;

Kashiwaya, K.; Ochiai, S.; Sakai, H. & Kawai, T. (2001). Orbital-related long-term climate

Koyama, M. & Matsushita, R. (1980). Use of neutron spectrum sensitive monitors for

Kravchinsky, V. A.; Krainov, M. A.; Evans, M. E.; Peck, J. A.; King, J. W.; Kuzmin, M. I.;

Laskar, J.; Joutel, F. and Boudin, F. (1993) Orbital, precessional, and insolation quantities for

*Research*, Vol.50, No.1, (March 2001), pp. 46-55, ISSN 0033-5894

Nos.1-4, (July 2004), pp. 227-243, ISSN 0031-0182

No.6824, (March 2001), pp. 71-74, ISSN 0023-0836

<http://hdl.handle.net/2433/76875>

(March 1993), pp. 522-533, ISSN 0004-6361

298, ISSN 0031-0182

and geochemistry of diatomaceous mud in Lake Baikal: global aspect. *Geologiya i Geofizika (Russian Geology and Geophysics)*, Vol.42, No.2, (February 2001), pp. 317-

Khlystov, O. M.; Ivanov, E. V.; Weinberg, E. & Gvozdkov, A. N. (2010). Uranium isotopes as proxies of the environmental history of the Lake Baikal watershed (East Siberia) during the past 150 ka. *Palaeogeography Palaeoclimatology Palaeoecology*,

O. M. & Zolotarev, K. V. (2005). Scanning SRXF analysis and isotopes of uranium series from bottom sediments of Siberian lakes for high-resolution climate reconstructions. *Nuclear Instruments and Methods in Physics Research Section A: Accelerations, Spectrometers, Detectors and Associated Equipment,* Vol.543, No.1, (May

Prell, W. L. & Shackleton, N. J. (1984). The orbital theory of Pleistocene climate: support from a revised chronology of the marine 6180 record, In: *Milankovitch and Climate, part 1*, Berger, A.; Imbrie, J.; Hays, J.; Kukula, G. & Saltzman, B., (Ed.), pp.

Lake Baikal for Siberian glaciation during Oxygen-Isotope substage 5d. *Quaternary* 

Solotchina, E.; Tkachenko, L. Fedenya, S.; Kerber, E.; Gvozdkov, A.; Khlustov, O.; Bezrukova, E.; Letunova, P. & Krapivina, S. (2004). Ecological collapse of Lake Baikal and Lake Hovsgol ecosystems during the Last Glacial and consequences for aquatic species diversity. *Palaeography, Palaeoclimatology, Palaeoecology*, Vol.209,

cycles revealed in a 12-Myr continental record from Lake Baikal. *Nature*, Vol.410,

instrumental neutron activation analysis. *Bulletin of the Institute for Chemical Research, Kyoto University*, Vol.58, No.2, (August 1980), pp. 235-243, Retrieved from

Sakai, H.; Kawai, T. & Wiiliams, D. F. (2003). Magnetic record of Lake Baikal sediments: chronological and paleoclimatic implication for the last 6.7 Myr. *Palaeography, Palaeoclimatology, Palaeoecology*, Vol.195, Nos.3-4, (June 2003), pp. 281-

the Earth from -20 Myr to +10 Myr. *Astronomy and Astrophysics*, Vol.270, Nos.1-2,

Vol.429, No.6992, (June 2004), pp. 623-628, ISSN 0023-0836

Vol.294, Nos.1-2, (August 2010), pp. 16-29, ISSN 0031-0182

325, ISSN 1068-7971

2005), pp. 250-254, ISSN 0168-9002


**8** 

*Japan* 

**Continental Erosion/Weathering Changes in Central Asia Recorded in the Holocene** 

**Sediment from Lake Hovsgol, Northwest** 

*5Association of International Research Initiatives for Environmental Studies* 

Nagayoshi Katsuta1, Takuma Murakami2,3, Yuko Wada2, Masao Takano2,

Lake Hovsgol (Fig. 1) is located in the southernmost part of the Baikal rift valley basins and occupies the second largest basin next to Lake Baikal. The lake lies 1645 m above sea level, and its surface area is 2,760 km2 (136 km long, 20~40 km wide). It has a water volume of 380.7 km3 and a maximum depth of 262.4 m (Goulden et al., 2006). The lake is surrounded by three types of vegetation regions: taiga-forest, steppe, and steppe-forest. The annual mean temperature is below zero (above zero during May to September), and the precipitation is 300~500 mm per year, most of which falls from April to October (Namkhaijantsan, 2006). The lake water contains Ca2+ at 797 μM. Its alkalinity is 2.60 (mEq/L), and it has a pH of 8.1 (Hayakawa et al., 2003). Geophysical observations reveal that Hovsgol's sediment is several kilometers thick (Fedotov et al., 2006), which suggests that the sedimentary sequences may document a long-term history of environmental

Recent studies on Lake Hovsgol cores indicate that the sediment chemistry records are important sources of information to understand environmental variations in the region and related climate changes. Oscillations in the climate proxy data acquired by stack of elements hosted in the carbonates and organic matter have been found to coincide with abrupt climate shifts in the Holocene and the last glacial/Holocene transition observed in the North Atlantic region (Fedotov et al., 2004a). Periodic variations in the 21 chemical elements in the bulk-sediment suggested that moisture change in central Asia occurred on glacialinterglacial scales, as well as with a period of ~8.7 kyr, through the last glacial/Holocene (Murakami et al., 2010). Phedorin et al. (2008) analyzed the past 1 Myr geochemical records

**1. Introduction** 

changes in arid central Asia.

**Mongolia, by Synchrotron μ-XRF** 

*2Graduate School of Environmental Studies, Nagoya University 3Low Level Radioactivity Laboratory, Kanazawa University 4Environment Safety Center, Tokyo University of Science* 

Masayuki Kunugi4 and Takayoshi Kawai2,5

**Mapping Analyses** 

*1Faculty of Education, Gifu University* 

