16 1 Vol. 16, No. 1 2004 3 CHIN ESE JOURNAL OF POLAR RESEARCH March 2004 (, 100029) (, 100085) (, 100029) 10 Be 26 Al, 2Ma, (L GM), 200m,, (L GM), 10 Be 26 Al 1 2600 km 3, 83 %, 60 (Denton,2002),,, (Denton et al., 1991 ; Ing lfsson et al., 1998 ; Anderson, 1999 ;Denton et al.,1984),, (Dowsett et al.,1996) [ ] 2003 12,2004 2 [ ] (2001DIA50040) [ ],,1974,
1 : 23,, (Clapperton Dugden,1991 ; Warnke et al.,1996 ; Sugen et al.,1995), 1/ 3 ( Webb Harwood,1990 ; Wilson, 1995) (Lal,1991 ;Nishiizumi et al.,1991 ; Ivy2Ochs et al.,1995 ; Sch afer et al.,1999 ;,1997 ;,1999) 10 Be 26 Al ( Grove Mountains) (Zakharoff Ridge) (Mount Harding),, 440km, 72 20 73 10 S, 73 50 75 40 E 64 (Liu et al., 2003), 3200km 2, 1800 1900m, 2000 2100m,, (Denton Hughs,2002 ; Huybrechts,2002) 15 16 19 1998 2002, (Liu et al.,2003 ;Li et al.,2003 ;,2003),, 100m,, 120m 10 Be 26 Al, 2 (Zakharoff Ridge) (Mount Harding) ( ) ( 1), 2250m, 150m, 2300m, 200m, (,2002 ;Liu et al.,2003), 4, 30 %, 0. 1 0. 5cm R8201,R8205, 2230m,R9201 2001, 20m 1
24 16 1 Fig. 1. Map of the Grove Mountains showing sample locations, 0. 1 1mm,, 1 % HF 1 % HNO 3 4 5,, 0. 5mg 9 Be Be Al, 850 C ( Kohl Nishiizumi,1992) 10 Be 26 Al (Australian Nuclear Science & Technology Orgnisation, ANSTO) (AMS) Al ( ICP2AES), Al 10 2 ppm ( 1),, 1 % 10 Be/ 9 Be 0. 5 10-14 1. 3 10-14, 3 10 Be 26 Al : N = P ( + / ) - ( + [1 - e / ) T ] + N 0 e - T (1) N ( / ), P ( / ), T ( ), ( / ),, ( / ), ( / ) N 0, 0 (Nishiizumi et al.,1991 ;Lal,1991), 0 10 Be 26 Al
1 : 25, 10 Be 26 Al Stone (2000), 10 Be 26 Al 5. 1 / 31. 1 / Stone (2000), 200m, Stone (2000) Dunai (2000), Lal (1991) Stone (2000) 1 1 Table 1. Altitudes and minimum exposure ages of the bedrock samples in the Grove Mountains Al 10Be/ 9 Be 26Al/ Al (m) ( 10-6 ) a (g) (10-12 ) ( %) (10-12 ) ( %) 10Be (10 6 / ) 26Al (10 6 / ) 26Al/ 10 Be 10Be (Ma) 26Al (Ma) R8201 2256 180 12. 4 21. 3 4. 1 58. 2 0. 6 57. 9 234. 5 4. 05 0. 26 2. 08 + 0. 15/ - 0. 14 2. 08 0. 04/ - 0. 03 R8203 2243 185 13. 6 14. 3 1. 6 44. 2 4. 8 48. 8 183. 0 3. 74 0. 39 1. 61 0. 04 1. 18 + 0. 26/ - 0. 21 R8205 2230 478 11. 0 16. 9 2. 8 18. 1 9. 1 50. 6 193. 5 3. 82 0. 29 1. 73 + 0. 08/ - 0. 07 1. 34 + 0. 21/ - 0. 18 R9201 2300 748 10. 7 19. 7 0. 5 13. 2 1. 9 63. 1 219. 9 3. 48 0. 19 2. 30 0. 02 1. 60 + 0. 23/ - 0. 19 R9207 2216 119 12. 5 26. 9 8. 2 73. 6 3. 1 73. 1 196. 3 2. 69 0. 27 3. 49 + 0. 86/ - 0. 62 b 1. 41 + 0. 20/ - 0. 17 : 10 Be 26 Al ( 10 %, Gosse et al.,2001). aicp2aes 5 %. b. 4 1 2Ma R9201 ( 200m) 10 Be 26 Al ( 2. 30 0. 02) Ma (1. 60 + 0. 23/ - 0. 19) Ma,, R8201 10 Be 26 Al (2. 08 + 0. 15/ - 0. 14) Ma (2. 08 + 0. 04/ - 0. 03) Ma, R9201 R9207 10 Be, 10 Be 26 Al, 10 Be 26 Al, 10 Be 10 Be/ 26 Al 10 Be 2, R8201, R8203,R8205 R9201,,, R9207, 10 Be, R9201,,,
26 16, R9201 (2300m), 200m, (L GM),L GM (Bentley,1999), 10 2 m (Jouzel,1989),, 200m, L GM R8205 2230m,, LM G, 2 26 Al/ 10 Be 10 Be 10 Be Fig. 2. Plot of 26 Al/ 10 Be vs. 10 Be concentrations. 10 Be concentrations have been normalized to sea level, high latitude of northern hemisphere 1 0,, Nishiizumi et al. (1991) cm/ Ma Ivy2Ochsd et al. (1995) 5cm/ Ma Lal (1991) Stone Ivy2Ochsd 5cm/ Ma, 5cm/ Ma R9201 R8201 10 Be, (4. 54 + 1. 42/ - 0. 71) Ma (3. 44 + 0. 92/ - 0171) Ma,,, (Joseph et al.,2002 ;Crowley,1991) 5 10 Be 26 Al
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28 16 Liu X, Zhao Y, Liu X et al. (2003) : Geology of the Grove Mountains in East Antarctic, Science in China (Series D), v. 46, 305 319. Miller MF, Mabin MCG (1998) : Antarctic Neogene landscape in the refrigerator or in the deep freeze? GSA Today, 8, 1 3. Nishiizumi K, Kohl CP, Arnold J R et al. (1991) : Cosmic ray produced 10 Be and 26 Al in Antarctic rocks : exposure and ero2 sion history, Earth and Planetary Science Letters, 104, 440 454. Sch afer J M, Ivy2Ochs S, Wieler R et al. (1999) : Cosmogenic noble gas studied in the oldest landscape on earth : surface exposure ages of the Dry valleys, Antarctica, Earth and Planetary Science Letters, 167, 215 226. Stone JO (2000) : Air pressure and cosmogenic isotope production, Journal of Geophysical Research, 105, 23,753 23, 759. Sugen DW, Marchant DR., Potter N et al. (1995) : Preservation of Miocene glacier ice in the East Antarctic, Nature, 376, 412 414. Warnke DA, Marzo B, Hodell DA (1996) : Major deglaciation of east Antarctic during the early Pliocene? Not Likely from marine perspective, M arine Micropaleontology, 27, 237 251. Webb PN, Harwood DM, Dugden DE (1990) : Late Cenozoic glacial history of the Ross Embayment, Antarctic, Quater2 nary Science Reviews, 10, 215 223. Wilson GS (1995) : The Neogene east Antarctic ice sheet : A dynamic or stable feature? Quaternary Science Reviews, 14, 101 123. BEDROCK EXPO SURE A GES IN THE GROVE MOUNTAINS, INTERIOR EAST ANTARCTICA Huang Feixin (Laboratory of Lithosphere Tectonic Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100101, China) Liu Xiaohan ( Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100085, China) Kong Ping, J u Yitai, Fang Aimin, Li Xiaoli, Na Chunguang ( Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100101, China) Abstract Exposure ages of bedrock samples taken f rom two nunataks in t he Grove Mountains ( GMs), interior East Antarctica, are studied by dating i n sit u produced cosmogenic 10 Be and 26 Al. The results indicate that the minimum exposure time of the five samples are all about 2Ma, much older than that of Last Glacial Maximum. This as well as the field obser2 vations indicates that the thickness of the interior East Antarctic Ice Sheet ( EAIS) had re2 duced more than 200m since early to middle Pliocene. From then on, even in the period of the Last Glacial Maximum (L GM), the elevation of the interior EAIS is never higher than that of early to middle Pliocene Key words east Antarctic ice sheet, Grove Mountains, Pliocene, 10 Be and 26 Al, exposure ages, deglaciation.