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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 210097, China 2. department of geology and {3., university of minnesota, minneapolis mn5.45., usa 1. College of Geography Science Nanjing Normal University Jiangsu Key Laboratory of Environmental Change and Ecological Construction Nanjing 210097 China 2. department of geology and geophysics University of Minnesota Minneapolis MN 55455 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 3.-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 245±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 2.3.‰, more than half of the δ 18O excursion between glacial/interglacial periods, and lasts 13.1±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.

Holocene grassland vegetation, climate and human impact in central eastern Inner Mongolia

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Science China Earth Sciences 2005年第7期48卷 1025-1039页

作者： HUANG Fei1, Kealhofer Lisa2, XIONG Shangfa3.& HUANG Fengbao1 1. Nanjing Institute of geology and Paleontology,Chinese Academy of Sciences,Nanjing 210008,China 2. Anthropology and Sociology department,Santa Clara university,CA 95053.{3. 3. Institute of geology and geophysics,Chinese Academy of Sciences,Beijing 100029,China Nanjing Institute of geology and Paleontology Chinese Academy of Sciences Nanjing 210008 China Anthropology and Sociology department Santa Clara University CA 95053 United States Institute of geology and Geoohysics Chinese Academy of Sciences Beijina 100029 China

Phytolith and pollen preserved in the Taipusi Banner paleosol profile, central eastern Inner Mongolia, provide evidence of Holocene grassland vegetation, climate and human impact. The combined phytolith and pollen records reveal a major change in vegetation composition about 5000 a BP. Before 5000 a BP, the vegetation was dominated by Aneurolepidium Chinese-Stipa grandis grassland of C4 grasses. After 5000 a BP, C4 grasses rapidly retreated, indicating a shift to colder and more arid conditions. The gradual invasion of Stipa krylovii, Ag-ropyron desertorum, Ephedra, Chenopodiaceae and Caragana reveal the onset of grassland degeneration. Between 10000 and 8720 a BP, the Aneurolepidium Chinese-Stipa grandis grassland included a small proportion of Artemisia shrub and Echionopos type plants, implying a strong winter monsoon and very weak summer monsoon. From 8720 to 7000 a BP, C4 grasses were common, indicating a strengthening of the summer monsoon. Between 7000 and 5000 a BP, the Holocene thermal maximum was evident, with a significant expansion of C4 grasses and the presence of some trees (such as Pinus and Betula, and so on) in or near the study site. From 4200?000 a BP, a sandy grassland of Artemisia and Agropyron desertorum together with Aster-type taxa occurred. Precipitation amelioration took place between 3.00 and 2170 a BP, with a rapid development of Echinops type plants and a small expansion of C4 grasses. From 2170 a BP to present, human activities accelerated the process of grassland degeneration.

关键词： phytolith and pollen records grassland environment change human impact Holocene central eastern Inner Mongolia.

Assessment of the modulated gradient model in decaying isotropic turbulence

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Theoretical & Applied Mechanics Letters 2011年第4期1卷 23-27页

作者： Hao Lu a) Saint Anthony Falls Laboratory,department of Civil Engineering,university of minnesota-Twin Cities,2 3.d Ave.SE,{3.,mn 55414,usa Saint Anthony Falls Laboratory Department of Civil Engineering University of Minnesota-Twin Cities 23rd Ave. SE Minneapolis MN 55414 USA

A recently introduced nonlinear model undergoes evaluations based on two isotropic turbulent cases:a university of Wiscosion-Madison case at a moderate Reynolds number and a Johns Hopkins university case at a high Reynolds *** model uses an estimation of the subgrid-scale(SGS) kinetic energy to model the magnitude of the SGS stress tensor,and uses the normalized velocity gradient tensor to model the structure of the SGS stress *** is performed for the first case through a comparison between direct numerical simulation(DNS) results and large eddy simulation(LES) results regarding resolved kinetic energy and energy *** the second case,we examine the resolved kinetic energy,the energy spectrum,as well as other key statistics including the probability density functions of velocities and velocity gradients,the skewness factors,and the flatness *** using the model are numerically stable,and results are satisfactorily compared with DNS results and consistent with statistical theories of turbulence.

关键词： large-eddy simulation subgrid-scale model isotropic turbulence

High resolution stalagmite δ18O records over the past 1000 years from Dongge Cave in Guizhou

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Science Bulletin 2005年第10期50卷 1003-1008页

作者： HE Yaoqi1, WANG Yongjin1, KONG Xinggong1 & CHENG Hai2 1. College of Geography Science, Nanjing Normal university, Nanjing 210097, China 2. department of geology and {3., minnesota university, Mineapolis mn 5.45., usa College of Geography Science Nanjing Normal University Nanjing 210097 China

Based on MC-ICP-MS U-series dating and stable O-isotope analysis results, a 4―5 years resolution monsoon record over the past 1000 years has been estab- lished for two stalagmites from Dongge Cave, Guizhou. The high resolution oxygen isotope record serves as a proxy for variations in rainfall of Asian southwest monsoon over the Yunnan-Guizhou Plateau. A close relation of the δ 18O record with the ?14C record from tree rings largely reflects impact of centennial-scale solar activity on the monsoon climate changes. The conspicuous decrease in the δ 18O value at AD 1720 indicates an abrupt increase in monsoon rainfall, sug- gesting that an atmospheric-oceanic couple over the tropical Indian Ocean plays an important role in rapid increase of the Northern Hemisphere temperature over the last century.

关键词： cave stalagmite oxygen isotope southwest monsoon solar activity Guizhou.

Postglacial sea-level changes and development stages of fluvial-estuarine system

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Acta Oceanologica Sinica 1993年第4期12卷 573-584页

作者： Li Congxian department of Marine geology and geophysics, Tongji {3., Shanghai 200092, China Dept. of Marine geology & geophysics Tongji Univ. Shanghai 200092 China

-On the basis of the data obtained from the investigations on some rivers in China and Australia, the author discusses the spatial and temporal changes of various portions of fluvial-estuarine system during postglacial sea-level rising in present coastal and deltaic areas. The evolution of a fluvial-estuarine system can be divided into four development stages: early transgression, late transgression, stationary and regression. Early transgression brought about filling-in of the paleo-valley formed in low stand of sea level. In response to late transgression the estuaries were created, during the stationary stage the big swamp was developed. The regression led to estuaries to be filled with sediments and then became deltas. At the same locality the fluvial-estuarine system changed with time. In the transgressive period the lower reach of a river changed into an estuary, and then became nearshore area. In the regressive period the nearshore area changed into an estuary , and then became delta.

关键词： Sea-level fluvial-estuarine system postglacial period paleo-valley paleo-interfluve retrogressive aggrada-tion

Effects of sleep deprivation on gamma oscillation of waking human EEG

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Progress in Natural Science:Materials International 2008年第12期18卷 1533-1537页

作者： Ning Li~a Yan Wang~a Mingshi Wang~a Haiying Liu~(a,b) a College of Precision Instrument and Opto-Electronics Engineering,Tianjin university,Tianjin 3.0072,China b department of Radiology university of minnesota,{3.,mn 5.45.,usa [a]College of Precision Instrument and Opto-Electronics Engineering Tianjin University Tianjin 300072 China [b]department of Radiology University of Minnesota Minneapolis MN 55455 USA

This study compares and evaluates the effect of sleep deprivation (SD) on human brain cognition by analyzing the recorded EEG data under normal and 24 h sleep deprived *** auditory event-related potentials were collected from 14 healthy volunteers,and the statistical values of wavelet-transformed EEG in gamma band were decomposed by parallel factor analysis (PARAFAC) to identify where the differences appeared in the time,frequency and spatial *** results showed that the changes of brain states caused by SD appeared around 40 Hz at about 400 ms after stimulation on prefrontal and frontal *** effects of SD on neuronal activity and oscillation were *** analysis of the EEG data by the wavelet transform and PARAFAC can be an integrated way to estimate the change of brain states in the three domains.

关键词： Gamma oscillation Sleep deprivation Event-related potential Wavelet transform Parallel factor Neuronal activity

Dehydration melting of solid amphibolite at 2.0 GPa: Effects of time and temperature

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Science China Earth Sciences 2005年第8期48卷 1120-1133页

作者： ZHOU Wenge1, XIE Hongsen1, LIU Yonggang1, ZHENG Xiaogang1, ZHAO Zhidan2 & ZHOU Hui3.1. Laboratory of Material in the Earth’s Interior, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China 2. department of geology, China university of Geosciences, Beijing 100083. China 3. department of geology, Peking university, Beijing 100871, China 1. Laboratory of Material in the Earth’s Interior Institute of Geochemistry Chinese Academy of Sciences 550002 Guiyang China 2. department of geology China University of Geosciences 100083 Beijing China 3. department of geology Peking University 100871 Beijing China

Two sets of dehydration-melting with a natural solid amphibolite, collected from North Himalayan structure zone, Tibet, have been carried out in multi-anvil apparatus at 2.0 GPa and 800―1000℃, for 12―200 h. One is keeping the pressure at 2.0 GPa and the annealing time of 12 h, changing the temperature (800―1000℃). The other is keeping the pressure at 2.0 GPa and temperature at 850℃, varying the annealing time (12―200 h). The products are inspected with microscope and electron probe. The results indicate that at 2.0 GPa, annealing time of 12 h, garnets, melts and clinopyroxenes occur in amphibolite gradually with increasing temperature and the chemical compositions of melt vary from tonalite to granodiorite, and then to tonalite. However, at 2.0 GPa and 850℃, with the annealing time increasing, the garnets, melts and cli-nopyroxenes also occur in amphibolite gradually and the chemical compositions of melt vary from tonalite to granodiorite. In both cases, melts interconnect with each other when the contents of melt are over the 5 vol.%. the viscosities of the melt produced in amphibolite at temperature higher than 850℃ are on a level with 104 Pa·s. The interconnected melt with such a viscosity may segregate from the source rock and form the magma over reasonable geological time. Therefore, it is believed that at the lower part of the overthickened crust, the tonlitic and grano-dioritic magma may be generated through the dehydration melting of amphibolite.

关键词： solid amphibolite, high pressure, high temperature, time, partial melting.

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 43.074,China 2. School of Environmental Studies,China university of Geosciences,Wuhan 43.074,China 3. SKLLQG,Institute of Earth Environment,Chinese Academy of Sciences,Xi’an 710075,China 4. department of {3. and geophysics,university of minnesota,mn5.45.,usa 1. Faculty of Earth Science China University of Geosciences 430074 Wuhan China 2. School of Environmental Studies China University of Geosciences 430074 Wuhan China 3. SKLLQG Institute of Earth Environment Chinese Academy of Sciences 710075 Xi’an China 4. department of geology and geophysics University of Minnesota 55455 MN 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 C26 in carbon number, maximizing at C16, with a second dominance at C22. In contrast to the stalagmite analysed, the overlying soils are characterized by the dominance of heavy-molecular-weight homologues (>C20). 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.

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 department, {3. university, mn5.45., usa 3. The Management of Maolan National Nature Reserve, Libo 558400, China 1. The Karst Dynamic Laboratory 541004 IKG CAGS Guilin China 2. geology and geophysics department Minnesota University 55455 MN USA 3. The Management of Maolan National Nature Reserve 558400 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, 8.27 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 8.27 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.