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No apparent lock-in depth of the Laschamp geomagnetic excursion: Evidence from the Malan loess

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Science China Earth Sciences 2006年第9期49卷 960-967页

作者： ZHU Rixiang1, LIU Qingsong1,2. PAN Yongxin1, DENG Chenglong1, ZHANG Rui1 & WANG Xianfeng3 1. Paleomagnetism and Geochronology Laboratory (SKL of Lithosphere Evolution), Institute of geology and geophysics, Chi- nese Academy of Sciences, Beijing 10002., China 2. Institute of geophysics and Planetary geophysics, university of California, Santa Cruz, CA 95064, usa 3. department of geology and geophysics, university of minnesota, Minneapolis, mn 55455, usa Paleomagnetism and Geochronology Laboratory (SKL of Lithosphere Evolution) Institute of Geology and Geophysics Chinese Academy of Sciences Beijing China Institute of geophysics and Planetary geophysics University of California Santa Cruz USA department of geology and {2. University of Minnesota Minneapolis USA

The first-order chronological framework of the long-term Chinese loess/paleosol sequences was based mainly on magnetostratigraphy. However, there remain arguments on the lock-in ages of the major geomagnetic reversals. This study systematically compared the stratigraphic locations of the Laschamp excursion and Henrich events (H4 at～39 ka and H5 at～48 ka) recorded by the Luochuan loess profile in the central Chinese Loess Plateau. Results show that the Lascchamp excursion is bracketed well by these two cold events, and the corresponding estimated age is between about 41.7-43.7 ka, which is close to the widely accepted age of ～40-41 ka for the ***, our new results do not suggest apparent lock-in effects in the last glacial Malan loess.

关键词： Chinese loess, Laschamp excursion, Henrich event, lock-in depth.

A possible Younger Dryas-type event during Asian monsoonal Termination 3

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Science China Earth Sciences 2006年第9期49卷 982-990页

作者： CHEN Shitao1, WANG Yongjin1, KONG Xinggong1, LIU Dianbing1, CHENG Hai2.& R.L. Edwards2.1. College of Geography Science, Nanjing Normal university, Jiangsu Key Laboratory of Environmental Change and Ecological Construction, Nanjing 2.0097, China 2. department of {2. and geophysics, university of minnesota, Minneapolis mn55455, usa College of Geography Science Nanjing Normal University Jiangsu Key Laboratory of Environmental Change and Ecological Construction Nanjing China department of geology and {2. University of Minnesota Minneapolis USA

Seven U-Th dates, 560 δ 18O data and microscopic sequences were measured for sta- lagmites from two high-altitude caves in Shennongjia area, Hubei Province. Variations of the de- cadal-resolution stalagmite δ 18O record from Swan Cave (1600 m elevation) reflect large spatial changes in circulation strength and precipitation of Asian monsoon. The evidence comes from a great similarity among the stalagmite δ 18O records from Nanjing, Jiangsu Province; Libo, Guizhou Province and here studied area during the last deglaciation, including a part interval of Younger-Dryas event and Bolling-Allerod. A 30-year-resolution stalagmite δ 18O record from Yongxing Cave (1400 m eleva- tion), 70 km away from Swan Cave, reveals a rapid transition of Asian monsoon climate during Ter- mination 3 at about 2.5±5 kaBP. Based on 3 U-Th dates and about 5000 continuous annual bands, a millennial dry episode has been observed during Asian monsoonal Termination 3 from the Yongxing δ 18O profile. With respect to its structure, duration and transition, the dry reversal, as indicated by our stalagmite δ 18O record, generally agrees with the pattern of the YD event well-expressed in the Chi- nese stalagmite δ 18O records. This YD-type event is characterized by a large decrease in δ 18O value as much as 2.30‰, more than half of the δ 18O excursion between glacial/interglacial periods, and lasts 1371±59 a determined by the annual counting chronology. After this event, the monsoon climate shifted abruptly into the interglacial period within 74±4 a. Our data corroborate the view that the re- peated occurrence of YD-type event was not an “accident”, possibly resulted from the coupling of ice-sheet and oceanic/atmospheric circulations.

关键词： stalagmite, Termination 3, Asian monsoon, YD-type event, Shennongjia, Hubei Province.

Abrupt climate change of EastAsian Monsoon at 130 kaBP inferred from a high resolu-tion stalagmite δ18O record

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Science Bulletin 2005年第23期50卷 2765-2769页

作者： JIANG Xiuyang1, WANG Yongjin1, KONG Xinggong1,WU Jiangying1, SHAO Xiaohua1, XIA Zhifeng1 & CHENG Hai2.1. College of Geography Science, Nanjing Normal university, Nanjing2.0097, China 2. department of {2. and geophysics, university of minnesotaMinneapolis, mn 55455, usa College of Geography Science Nanjing Normal University Nanjing 210097 China department of geology and {2. University of Minnesota Minneapolis MN 55455 United States

2.0Th ages and oxygen isotope data of a stalagmite from Shanbao Cave in Hubei Province characterize thEast Asian Monsoon precipitation from 133 to12. ka. Thdecadal-scale high-resolution δ18O record reveals a detailedtransitional process from the Penultimate Glaciation to thLast Interglaciation. As established with 2.0Th dates, the agof the Termination II is determined to be 12..5±1.0 kaBPwhich supports the Northern Hemisphere insolation as thtriggers for the ice-age cycles. In our δ18O record, the glacialinterglacial fluctuation reaches about 4‰, almost the samlevel as in other Asian Monsoon cave stalagmite δ18O recordThe transition of the glacial/interglacial period in our recordcan be recognized as four stepwise stages, among which, arapid rise of monsoon precipitation follows the stage o“Termination II pause”. The rapid rise is synchronous withthe abrupt change of global methane concentration, whichreflects that an increase in both Asian Monsoon precipitationand tropical wetland plays an important role in the globaclimate changes.

关键词： stalagmite high-resolution U/Th age Termination II.

The *** climate abrupt events in the early and middle Holocene:Stalagmite oxygen isotope record from Maolan,Guizhou,China

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Science China Earth Sciences 2005年第4期48卷 530-537页

作者： QIN Jiaming1, YUAN Daoxian1, CHENG Hai2. LIN Yushi1, ZHANG Meiliang1, WANG Fuxing1, R. L. Edwards2. WANG Hua1 & RAN Jingcheng3 1. The Karst Dynamic Laboratory, IKG, CAGS, Guilin 541004, China 2. geology and geophysics {2., minnesota university, mn55455, usa 3. The Management of Maolan National Nature Reserve, Libo 558400, China The Karst Dynamic Laboratory IKG CAGS Guilin China geology and geophysics {2. Minnesota University MN USA The Management of Maolan National Nature Reserve Libo China

The isotope records which range from 3.9 kaBP to 15.7 kaBP with an average resolution of 90 a have been obtained from 45 cm to 193.6 cm of the upper part of D4 stalagmite from Dongguo Cave in Libo, Guizhou, by using system TIMS U-series dating and carbon and oxygen stable isotope *** study indicates that the last cold event, the YD (Younger Dryas) event, of the last glacial period was apparently shown in D4 record, which started from 12.80 kaBP and ended in 11.58 kaBP, with a great range of drop in temperature. The end of the last glacial period was consistent with the termination I in oceanic isotope records and was with time limit of 11.3 kaBP. The three most distinct cold events in the early and middle Holocene occurred respectively in 10.91 kaBP, 8.2. kaBP and 4.75 kaBP, with a range of drop in tem- perature reaching 2.5℃. The climate abrupt events in thousand and hundred years scale re- corded in stalagmite δ O can be compared to those in GISP2.ice cores from Greenland in their 18 happening time and the range of their lasting time. The cold events in 8.2. kaBP and 4.75 kaBP can also be compared to CC3 stalagmite records in Ireland, which indicate that climate changes of short range in China monsoon areas, western Europe and polar regions, have the same driv- ing factor. This has a global significance. In addition, the trend of record curves in some time- stages is apparently different, which reflects probably the difference between environment in monsoon climate areas and in polar regions.

关键词： isotope record, climate event, stalagmite, Libo, Guizhou.

Distributions of fatty acids in a stalagmite related to paleoclimate change at Qingjiang in Hubei,southern China

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Science China Earth Sciences 2005年第9期48卷 1463-1469页

作者： XIE Shucheng1,HUANG Junhua1,WANG Hongmei2.YI Yi1,HU Chaoyong1, CAI Yanjun3 & CHENG Hai4 1. Faculty of Earth Science,China university of Geosciences,Wuhan 430074,China 2. School of Environmental Studies,China university of Geosciences,Wuhan 430074,China 3. SKLLQG,Institute of Earth Environment,Chinese Academy of Sciences,Xi’an 710075,China 4. {2. of geology and geophysics,university of minnesota,mn55455,usa Faculty of Earth Science China University of Geosciences Wuhan China School of Environmental Studies China University of Geosciences Wuhan China SKLLQG Institute of Earth Environment Chinese Academy of Sciences Xi’an China department of geology and {2. University of Minnesota USA

Fatty acids extracted from a subtropical stalagmite at Qingjiang in Southern China’s Hubei Province were analysed using gas chromatography-mass spectrometry. These n-alkanoic acids range from C14 to C2. in carbon number, maximizing at C16, with a second dominance at C2.. In contrast to the stalagmite analysed, the overlying soils are characterized by the dominance of heavy-molecular-weight homologues (>C2.). The n-fatty acids in the stalagmite were proposed to be contributed by both the soil ecosystems and the microbes harboring in the percolating water and the cave. The ratios of unsaturated to saturated n-fatty acids (C16:1i/C16:0, C18:1/C18:0) appear to show trends comparable with the oxygen isotope records of the stalagmite carbonate, with enhanced values associated with the cold episode such as Heinrich event 1. This paleoclimate-dependent record of the n-fatty acids might reflect microbial changes in physiology and activity in response to the temperature. This record shows somewhat difference from the previous paleoclimate signal extracted from n-alkanols and n-alkan-2.ones of the same stalagmite. The acid record fails to document the well-known Younger Dryas event which was effectively shown by the latter two biomarkers derived from soil ecosystems. This discrepancy might result from the changing biogeochemical impact on different lipid fractions as well as the varied organism populations in different ecosystems.

关键词： biomarker, ecosystem, microbe, speleothem, paleoclimate, Quaternary.

Rheology of Partially Molten Olivine Aggregates under Water-Saturated Conditions

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Continental Dynamics 1997年第1期 54-62页

作者： BAI Wuming (Institute of geophysics, Chinese Academy of Sciences, Beijing 100101, China) MEI Shenghua David KOHLSTEDT (department of {2. and geophysics, university of minnesota, mn 55455, usa)

The influence of basaltic melt and water content on the high-temperature plastic deformation behavior of olivine aggregates was studied by performing a series of high-temperature creep experiments. The specimens, which are the powder of San Carols olivine plus 1, 4, or 7 wt% MORB, with the grain size of 10-2. μm, were hotpressed. Deformation experiments were conducted in a gas-medium apparatus at a confining pressure of 300 MPa and temperature of 1373 K to 1473 K. Water was supplied by dehydration of TALC near 1073 K. The hy- droxyl concentration in the samples was determined from Fourier-Transform Infrared (FTIR) spectra.

关键词： partial melting water-saturated conditions rheology high pressure and high temperature

Stable isotope records of plant cover change and monsoon variation in the past 2.00 years:evidence from laminated stalagmites in Beijing,China

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Stable isotope records of plant cover change and monsoon var...