18 resultados para meanings

em Chinese Academy of Sciences Institutional Repositories Grid Portal


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In this paper, the penetration process of ogive-nose projectiles into the semi-infinite concrete target is investigated by the dimensional analysis method and FEM simulation. With the dimensional analysis, main non-dimensional parameters which control the penetration depth are obtained with some reasonable hypothesis. Then, a new semi-empirical equation is present based on the original work of Forrestal et al., has only two non-dimensional combined variables with definite physical meanings. To verify this equation, prediction results are compared with experiments in a wide variation region of velocity. Then, a commercial FEM code, LS-DYNA, is used to simulate the complex penetration process, that also show the novel semi-empirical equation is reasonable for determining the penetration depth in a concrete target.

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The similarity criterion for water flooding reservoir flows is concerned with in the present paper. When finding out all the dimensionless variables governing this kind of flow, their physical meanings are subsequently elucidated. Then, a numerical approach of sensitivity analysis is adopted to quantify their corresponding dominance degree among the similarity parameters. In this way, we may finally identify major scaling law in different parameter range and demonstrate the respective effects of viscosity, permeability and injection rate.

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The similarity criterion for water flooding reservoir flows is concerned with in the present paper. When finding out all the dimensionless variables governing this kind of flow, their physical meanings are subsequently elucidated. Then, a numerical approach of sensitivity analysis is adopted to quantify their corresponding dominance degree among the similarity parameters. In this way, we may finally identify major scaling law in different parameter range and demonstrate the respective effects of viscosity, permeability and injection rate.

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The thermal conductivity of periodic composite media with spherical or cylindrical inclusions embedded in a homogeneous matrix is discussed. Using Green functions, we show that the Rayleigh identity can be generalized to deal with thermal properties ot these systems. A new calculating method for effective conductivity of composite media is proposed. Useful formulae for effective thermal conductivity are derived, and meanings of contact resistance in engineering problems are explained.

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In this paper, the penetration process of ogive-nose projectiles into the semi-infinite concrete target is investigated by the dimensional analysis method and FEM simulation. With the dimensional analysis, main non-dimensional parameters which control the penetration depth are obtained with some reasonable hypothesis. Then, a new semi-empirical equation is present based on the original work of Forrestal et al., has only two non-dimensional combined variables with definite physical meanings. To verify this equation, prediction results are compared with experiments in a wide variation region of velocity. Then, a commercial FEM code, LS-DYNA, is used to simulate the complex penetration process, that also show the novel semi-empirical equation is reasonable for determining the penetration depth in a concrete target.

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Accurate, analytical series expressions for the far-field diffraction of it Gaussian beam normally incident on a circular and central obscured aperture are derived with the help of the integration of parts method. With this expression, the far-field intensity distribution pattern can be obtained and the divergence angle is deduced too. Using the first five items of the series, the accuracy can satisfy most laser application fields. Compared with the conventional numerical integral method, the series representation is very convenient for understanding the physical meanings. (C) 2007 Elsevier GmbH. All rights reserved.

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目前全球缺水、水污染、洪涝灾害以及水土流失仍然非常严重,尤其在我国北方地区。流域水文模型可用来进行不同需水管理的情景分析,为解决我国水问题提供科学依据。分布式水文模型是流域水文模型的发展方向,具有显著特点:1)应用前景广泛,不仅可以模拟流域水文过程,还可以协助模拟泥沙或污染物的运移过程,为水利工程设计、水土保持、环境保护等领域提供技术支持;2)能够预测流域土地利用或气候变化下的流域水文响应过程变化,为管理部门提供决策支持;3)模型所需要的参数全部具有物理意义,可通过实际测量确定,适合模拟实测系列较短或是无观测流域的水文过程;4)对于目前国际水文界的前沿问题—水文尺度转换提供了一种有效的解决途径。 然而分布式水文模型还不完善,如1)真实性问题。对一些水文过程和边界条件还不确定。2)尺度转换问题。目前很少考虑尺度对参数有效性的影响。3)检验问题。还无法判断对有些难以测量的水文状态变量的模拟正确与否。4)计算时间和数据存储的问题。有些分布式水文模型虽然具有很强的水文物理基础和完善的模型结构,但是计算时间过长和(或)数据存储过大,难以应用。上述问题的核心就是对分布式水文模型的核心—单元水文模型的研究不够,需要为进一步完善单元水文模型进行研究。 本文采用饱和入渗理论、Saint-Venant方程、Richards方程、Penman-Monteith方程等等构建了以有限差分法求解的适用于森林流域的单元水文模型,并通过实验室模拟试验和坡地径流场资料进行了验证,主要结论为: 通过不同坡度和不同雨强下的室内坡面产汇流实验模拟,表明:该模型模拟的坡面流和壤中流过程与实测过程基本一致,峰现时间、径流历时、峰值流量、出流总量模拟值与实测值的相对误差均较小,基本小于10%。模型的模拟精度较高,实用性较强,为深入研究壤中流机制和改进流域降雨-径流模型提供了理论依据。 通过坡地径流观测场实测资料的验证,表明:该模型模拟的坡面流过程精度较高,累计流量的精度更高于小时过程的精度,离差系数、效率系数、确定系数均较理想,具有应用价值,有助于改善分布式水文模型在森林流域的模拟效果。

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Seasonal investigations of size-fractionated biomass and production were carried out from February 1992 to May 1993 in Jiaozhou Bay, China. Microplankton assemblages were separated into three fractions: pico-(0.7-2 mu m), nano- (2-20 mu m) and netplankton (20-200 mu m). The biomass was measured as chlorophyll a (Chl a), particulate organic carbon (POC) and particulate organic nitrogen (PON). The production was determined by C-14 and N-15 tracer techniques. The seasonal patterns in biomass, though variable, were characterized by higher values in spring and lower values in autumn and summer (for Chl a only). The seasonal patterns in production, on the other hand, were more clear with higher values occurring in summer and spring, and lower values occurring in autumn and winter. Averaged over the whole study period, the respective proportions of total biomass accounted for by net-, nano- and picoplankton were 26, 45 and 29% for Chl a, 32, 33 and 35% for POC, and 26, 32 and 42% for PON. The contributions to total primary production by net-, nano- and picoplankton were 31, 35 and 34%, respectively. The respective proportions of total NH4+-N uptake accounted for by net-, nano- and picoplankton were 28, 33 and 39% in the daytime, and 10, 29 and 61% at night. The respective contributions to total NO3--N uptake by net-, nano- and picoplankton were 37, 40 and 23% in the daytime, and 13, 23 and 64% at night. Some comprehensive ratios, including C/N biomass ratio, Chl a/C ratio, C uptake/Chl a ratio, C:N uptake ratio and the f-ratio, were also calculated size separately, and their biological and ecological meanings are discussed.

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Petroleum and Natural Gas is an important strategic resources. The reserves of Petroleum and Natural Gas can’t meet the need of our country, which also blocks the development of economy and threatens the safety of national. Therefore, it makes a great sense to bring “the second round of oil & gas exploration” into effect and study the exploration of oil and gas of Pre-Cenozoic residual basins in China. The integrated geophysical exploration is the main way to research the Pre-Cenozoic residual basins. Gravity exploration is one of the most important exploration methods, which has played an important role in oil and gas prospecting, such as compartmentalizing geotectonic elements, delineating the distribution range of sedimentary basins, searching oil and gas structure, abstracting oil and gas information, and so on, from its naissance. The isostatic gravity anomalies is significant for exploration, which can help us research deep crustal structure, the equilibrium state of earth, the geologic structure of shallow crust, the basement shape of sedimentary basins and the genetic evolution of sedimentary basins. In the paper, we stress the implication and physical meanings systemically, and discuss the calculation theory. On the basis of previous work, we test different isostatic compensation models and parameters to find out their influences to the result of isostatic gravity anomalies. In addition, we improve the method of isostatic gravity anomalies calculation and give a system of isostatic gravity anomalies calculation which is proved has satisfying effect. From the research above, we find that the results of Platt model and Airy model are consistent, which have similar form and almost the same value. However, by contrast, the Airy model is proved has better adaptability than Platt model. The two main parameters——crust thickness and density difference of crust and mantle, both have influence to the isostatic gravity anomalies, but the latter have more. Finally, we adopt the regional field extending edge method to make the result more of actual geologic condition. On the methods above, we calculate the isostatic gravity anomalies field in Yellow Sea area from the Bouguer gravity anomalies and the water depth and altitude data. And then the isostatic gravity anomalies character is analyzed and the integrated geological-geophysical interpretation is made on the basis of summarizing the previous research result systemically and analyzing other geophysical data and geological information. From the research, we find that the Yellow Sea area belongs to continental type crust equilibrium regions, where the isostatic gravity anomalies field is placid and has less fluctuation values, which implies that the area is in equilibrium state to different extends.

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In this paper we base on the anisotropic theory and Zoeppritz function of the transmission theory and the law of amplitude versus offset simplify seismic reflection coefficient of different media, analyze the characteristic of the gas or oil saturated stratum or the VTI and HTI models. Discuss the P wave reflection relationship and the meanings of the different parameters. We use measured parameters of a reservoir to simulate the characteristic of the reservoir, study the different effects of stratum saturated with gas or oil and analyze the characteristic of the seismic response of different models which change with different incident angles and different azimuths. Using the field data of logs ,analyze the rock property parameters, build the relationship of logs and parameters by Gassmann theory or empirical function. Calculate the density and the shear modulus and bulk modulus, reconstruct the log curves, calculate shear wave logs and correlate the logs affected by mud and other environmental factors. Finally perform the relationship of the seismic data log of saturated stratum and enhance the ability and reliability in reservoir prediction. Our aim is by the prestack seismic processing to get high solution and amplitude preserved seismic data. Because in incident angle gathers or azimuthal gathers, the low signal to noise ratio and low different covers affect the result of the prestack reservoir prediction. We apply prestack noise erase, cell regularization process and relatively amplitude preservation in the high solution seismic process routine to preserve the characteristic of stratum response, and erase the effects of the noise. In this paper we finished prestack invertion in the BYT survey and fractured reservoir depiction in MB survey. By the invertion and multiple attributes crossplot. we can get the stratum profiles and oil indicator profiles which can predict the distribution of the reservoir and oil. In the MB survey, we get orientation and density of fractured reservoir by the azimuthal seismic amplitude and depict the potential oil and gas reservoir. Prestak invertion works better in distinguishing oil and reservoir.

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This article is an important part of "95" technological subject of SINOPEC. It has a large number of difficulties and workloads, and has significant theoretical meanings and practical value. The study area is composed of sandstone & conglomerate reservoir of alluvial fan & fan delta, which belong to Sha3 lower member and Sha4 upper member of lower tertiary of Yong'an Town Oilfield in Dongying Depression. The target stataum develops in the hanging wall of the synsedimentary fault in the scarp zone of Dongying Depression. The frequently intense movements result in the variation of sandstone and conglomerate reservoir and the evolution of the time and space of Sha3 lower member and Sha4 upper member in Yong'an Town Oilfield. As a result, it is difficult for the individual reservoir correlation at the root of fan, which bring about a tackle problem for the exploitation of oilfield. In this background, the research of fluid units will be more difficult. In this article, the new concepts, the new methods, and the new techniques of sedimentology, petroleum geology, reservoir geology, physics of crystal surface, dynamic & static state reservoir description and well logging geology are synthetically applied, and the computer technology are made full uses of, and the identifying, dividing and appraising of the two-formation-type sandstone & conglomerate reservoir fluid units of Sha3 lower member and Sha4 upper member systemically analyzed in Yong'an Town Oilfield, Dongying Depression. For the first time, the single-well model, the section model, the plane model, the nuclear magnetism log model, the microcosmic network model, the 4-D geology model and the simulation model of the two-formation-type reservoir fluid units of the of sandstone & conglomerate reservoir of Sha3 lower member and Sha4 upper member are established, and the formative mechanism and distributing & enrichment laws of oil-gas of the two type of sandstone and conglomerate reservoir fluid units are revealed. This article established the optimizing, identifying, classifying and appraising standard of the two-formation-type reservoir fluid units of the of sandstone and conglomerate reservoir of Sha3 lower member and Sha4 upper member, which settles the substantial foundations for static state model of the fluid units, reveals the macroscopic & microcosmic various laws of geometrical static state of the fluid units, and instructs the oil exploitation. This article established static state model of the two-formation-type sandstone and conglomerate reservoir fluid units by using the multi-subject theories, information and techniques, and reveals the geometrical configuration, special distribution and the oil-gas enrichment laws of the sandstone and conglomerate reservoir fluid units. For the first time, we established the nuclear magnetism log model of the two-formation-type sandstone and conglomerate reservoir of Sha3 lower member and Sha4 upper member, which reveals not only the character and distributing laws of the porosity and permeability, bat also the formation and distribution of the movable fluid. It established six type of microcosmic net model of the two-formation-type sandstone and conglomerate reservoir of Sha3 lower member and Sha4 upper member in the working area by using the advanced theories, such as rock thin section, SEM, image analysis, intrusive mercury, mold, rock C.T. measure & test image etc., which reveals the microcosmic characteristic of porosity & throat, filterate mode and microcosmic oil-gas enrichment laws of the sandstone and conglomerate reservoir. For the first time, it sets up the 4-D model and mathematic model of the sandstone and conglomerate reservoir, which reveals the distributing and evolving laws of macroscopic & microcosmic parameters of the two-formation-type sandstone and conglomerate reservoir and oil-gas in 4-D space. At the same time, it also forecasts the oil-gas distribution and instructs the oilfield exploitation. It established reservoir simulation model, which reveals the filterate character and distributing laws of oil-gas in different porosity & throat net models. This article established the assistant theories and techniques for researching, describing, indicating and forecasting the sandstone and conglomerate reservoir fluid units, and develops the theories and techniques of the land faces faulted basin exploitation geology. In instructing oilfield exploitation, it had won the notable economic & social benefits.

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The study of biogenic proxy of tropical and subtropical regions provides important evidence about the process and history of vegetation and environmental changes, and is of globally importance for understanding the dynamic mechanism of paleoclimatic and paleoenvironmental changes. The sediments from the Huguangyan Maar lake in Guangdong Province offer a continuous high-resolution record of the past 55 ka about environmental and vegetational changes. The studies of chronology, and physical, chemical environmental proxies have provided much important information about the paleoenvironmental and paleoclimatic histories. The phytolith, a new biogenicl proxy, has been used to determine the nature and types of plants in this area since the last 55 ka. This study presents a preliminary result about the characteristics of phytolith shapes, the variations of the fossils assemblages, and their significance for environmental changes. Moreover, the author probes the process of special specie evolution and their relationship to climatic parameters. The history of fire has been reconstructed based on the variations in charcoals. The main results and conclusions include: 28 types of phytoliths from 233 samples have been identified. Their environmental meanings are investigated in detail. Based on the variations in phytolith associations, the history and process of climatic and environmental changes in the last 55 kaBP have been established for this region. Climatic changes experienced eight intervals during this period, showing the variations of hot-humid to cool-try climate in the ten thousands years scale, and a shorter dry-hot climate condition in millennial scale. The history of palm plant has been established in this region. Two peaks appeared from 55-39 ka and since the Holocene. Plants in Bambusoideae have been growing in this area all the period, representing the impact of the East Asian summer monsoon. Bamboo plants have similar tendency in their abundance to palm plants, but with a lag of 1-2 ka BP. Panicoideae plants, the representative of C4 plants, have 6 flourishing periods occurred at 54.5, 44, 41.5, 32.5, 14, and 10 kaBP, respectively, reflecting 6 times short-term arid events. Charcoal record from the Huguang Marr lake reveals the history of nature fire, that mostly happened in dry period of last glacial from 55-10 kaBP, centered at 50-45, 40-35, 30-25, and 20-15kaBP, showing about a cycle of 10,000 years.

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Ordos Basin is a typical cratonic petroliferous basin with 40 oil-gas bearing bed sets. It is featured as stable multicycle sedimentation, gentle formation, and less structures. The reservoir beds in Upper Paleozoic and Mesozoicare are mainly low density, low permeability, strong lateral change, and strong vertical heterogeneous. The well-known Loess Plateau in the southern area and Maowusu Desert, Kubuqi Desert and Ordos Grasslands in the northern area cover the basin, so seismic data acquisition in this area is very difficult and the data often takes on inadequate precision, strong interference, low signal-noise ratio, and low resolution. Because of the complicated condition of the surface and the underground, it is very difficult to distinguish the thin beds and study the land facies high-resolution lithologic sequence stratigraphy according to routine seismic profile. Therefore, a method, which have clearly physical significance, based on advanced mathematical physics theory and algorithmic and can improve the precision of the detection on the thin sand-peat interbed configurations of land facies, is in demand to put forward.Generalized S Transform (GST) processing method provides a new method of phase space analysis for seismic data. Compared with wavelet transform, both of them have very good localization characteristics; however, directly related to the Fourier spectra, GST has clearer physical significance, moreover, GST adopts a technology to best approach seismic wavelets and transforms the seismic data into time-scale domain, and breaks through the limit of the fixed wavelet in S transform, so GST has extensive adaptability. Based on tracing the development of the ideas and theories from wavelet transform, S transform to GST, we studied how to improve the precision of the detection on the thin stratum by GST.Noise has strong influence on sequence detecting in GST, especially in the low signal-noise ratio data. We studied the distribution rule of colored noise in GST domain, and proposed a technology to distinguish the signal and noise in GST domain. We discussed two types of noises: white noise and red noise, in which noise satisfy statistical autoregression model. For these two model, the noise-signal detection technology based on GST all get good result. It proved that the GST domain noise-signal detection technology could be used to real seismic data, and could effectively avoid noise influence on seismic sequence detecting.On the seismic profile after GST processing, high amplitude energy intensive zone, schollen, strip and lentoid dead zone and disarray zone maybe represent specifically geologic meanings according to given geologic background. Using seismic sequence detection profile and combining other seismic interpretation technologies, we can elaborate depict the shape of palaeo-geomorphology, effectively estimate sand stretch, distinguish sedimentary facies, determine target area, and directly guide oil-gas exploration.In the lateral reservoir prediction in XF oilfield of Ordos Basin, it played very important role in the estimation of sand stretch that the study of palaeo-geomorphology of Triassic System and the partition of inner sequence of the stratum group. According to the high-resolution seismic profile after GST processing, we pointed out that the C8 Member of Yanchang Formation in DZ area and C8 Member in BM area are the same deposit. It provided the foundation for getting 430 million tons predicting reserves and unite building 3 million tons off-take potential.In tackling key problem study for SLG gas-field, according to the high-resolution seismic sequence profile, we determined that the deposit direction of H8 member is approximately N-S or NNE-SS W. Using the seismic sequence profile, combining with layer-level profile, we can interpret the shape of entrenched stream. The sunken lenticle indicates the high-energy stream channel, which has stronger hydropower. By this way we drew out three high-energy stream channels' outline, and determined the target areas for exploitation. Finding high-energy braided river by high-resolution sequence processing is the key technology in SLG area.In ZZ area, we studied the distribution of the main reservoir bed-S23, which is shallow delta thin sand bed, by GST processing. From the seismic sequence profile, we discovered that the schollen thick sand beds are only local distributed, and most of them are distributary channel sand and distributary bar deposit. Then we determined that the S23 sand deposit direction is NW-SE in west, N-S in central and NE-SW in east. The high detecting seismic sequence interpretation profiles have been tested by 14 wells, 2 wells mismatch and the coincidence rate is 85.7%. Based on the profiles we suggested 3 predicted wells, one well (Yu54) completed and the other two is still drilling. The completed on Is coincident with the forecastThe paper testified that GST is a effective technology to get high- resolution seismic sequence profile, compartmentalize deposit microfacies, confirm strike direction of sandstone and make sure of the distribution range of oil-gas bearing sandstone, and is the gordian technique for the exploration of lithologic gas-oil pool in complicated areas.

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Saprolite is the residual soil resulted from completely weathered or highly weathered granite and with corestones of parent rock. It is widely distributed in Hong Kong. Slope instability usually happens in this layer of residual soil and thus it is very important to study the engineering geological properties of Saprolite. Due to the relic granitic texture, the deformation and strength characteristics of Saprolite are very different from normal residual soils. In order to investigate the effects of the special microstructure on soil deformation and strength, a series of physical, chemical and mechanical tests were conducted on Saprolite at Kowloon, Hong Kong. The tests include chemical analysis, particle size analysis, mineral composition analysis, mercury injection, consolidation test, direct shear test, triaxial shear test, optical analysis, SEM & TEM analysis, and triaxial shear tests under real-time CT monitoring.Based on the testing results, intensity and degree of weathering were classified, factors affecting and controlling the deformation and strength of Saprolite were identified, and the interaction between those factors were analyzed.The major parameters describing soil microstructure were introduced mainly based on optical thin section analysis results. These parameters are of importance and physical meaning to describe particle shape, particle size distribution (PSD), and for numerical modeling of soil microstructure. A few parameters to depict particle geometry were proposed or improved. These parameters can be used to regenerate the particle shape and its distribution. Fractal dimension of particle shape was proposed to describe irregularity of particle shapes and capacity of space filling quantitatively. And the effect of fractal dimension of particle shape on soil strength was analyzed. At the same time, structural coefficient - a combined parameter which can quantify the overall microstructure of rock or soil was introduced to study Saprolite and the results are very positive. The study emphasized on the fractal characteristics of PSD and pore structure by applying fractal theory and method. With the results from thin section analysis and mercury injection, it was shown that at least two fractal dimensions Dfl(DB) and Df2 (Dw), exist for both PSD and pore structure. The reasons and physical meanings behind multi-fractal dimensions were analyzed. The fractal dimensions were used to calculate the formation depth and weathering rate of granite at Kowloon. As practical applications, correlations and mathematical models for fractal dimensions and engineering properties of soil were established. The correlation between fractal dimensions and mechanical properties of soil shows that the internal friction angle is mainly governed by Dfl 9 corresponding to coarse grain components, while the cohesion depends on Df2 , corresponding to fine grain components. The correlations between the fractal dimension, friction angle and cohesion are positive linear.Fractal models of PSD and pore size distribution were derived theoretically. Fragmentation mechanism of grains was also analyzed from the viewpoint of fractal. A simple function was derived to define the theoretical relationship between the water characteristic curve (WCC) and fractal dimension, based on a number of classical WCC models. This relationship provides a new analytical tool and research method for hydraulic properties in porous media and solute transportation. It also endues fractal dimensions with new physical meanings and facilitates applications of fractal dimensions in water retention characteristics, ground water movement, and environmental engineering.Based on the conclusions from the fractal characteristics of Saprolite, size effect on strength was expressed by fractal dimension. This function is in complete agreement with classical Weibull model and a simple function was derived to represent the relationship between them.In this thesis, the phenomenon of multi-fractal dimensions was theoretically analyzed and verified with WCC and saprolite PSD results, it was then concluded that multi-fractal can describe the characteristics of one object more accurately, compared to single fractal dimension. The multi-fractal of saprolite reflects its structural heterogeneity and changeable stress environment during the evolution history.

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自20世纪60年代以来,探索全球性气候变化规律和环境变迁史的研究工作在世界各国广泛开展。大规模的深海岩芯的研究、中国北方黄土的系统研究、大型湖泊沉积岩芯的研究及对树木年轮、泥炭、珊瑚、冰芯等“自然环境历史档案”开展的研究工作,都为重建古气候和古生态环境提供了大量的资料。洞穴化学沉积物(石笋)由于其特有的微层结构及其内的稳定氧、碳同位素和微量元素所蕴含的古气候与古生态环境信息,并且具有分布广、时间长、信息保存完整等特点,因此,它是研究地球环境变化很好的自然环境历史档案。本论文通过对凉风洞洞穴体系的综合研究和对凉风洞石笋(微层)生长特征及石笋的碳、氧稳定同位素组成的研究,系统探讨了贵州凉风洞石笋的古气候记录和古生态环境意义,得出以下主要结论:1,地表植被的类型及生物量等信息可综合反映于洞穴体系的不同组.分(气样、土样、水样)中。而洞穴的水动力条件也能很好的被洞穴滴水中所含微量(常量)元素记录。根据分析,洞穴综合体系对外界气候与生态环境的响应关系存在一定规律性。通过对比说明,我们所选的凉风洞基岩的溶蚀和缓冲对水体中的信息影响不大,即洞穴滴水较好的继承了土壤水所携带的地表气候与生态环境信息,是理想的研究对象。2.凉风洞石笋具有多个沉积旋回,不同沉积旋回的纹层组合及纹层结构存在一定的差异,指示不同的沉积环境。根据年龄数据判断,旋回①至旋回⑧之间年龄跨度为1570-8000 aBP,以呈缓平顶(柱)对称叠复状的沉积形态组合为主,示洞顶滴水量较大,滴水点相对稳定,且均匀,与全新世较为稳定的气候与环境变化的主旋律相一致。旋回⑧以下至底部石葡萄状沉积物之上部分之间年龄跨度为8000-14220 aBP,期间经历末次冰期晚期向全新世大暖期过渡,受诸如新仙女木事件(Younger Dryas)等的影响,气候变化幅度大,且经历多次反复,石笋生长的沉积学特征表现为斜锥(柱)、尖顶锥不对称叠复纹层组合,示洞顶滴水水量较小但变化较大,且洞穴滴水不稳(固)定。与此时间段内不稳定的气候与环境变化的主旋律也相一致。3.凉风洞石笋上段微层具有典型南方石笋微层发育的特性:微层发育较差,层面多弯曲,层间界面模糊等。下段因为沉积间断较多、风化层面厚及受到若干时段内碳酸钙重结晶而导致晶体穿插层位生长的影响,尽管在某些层位有微层发育,但无法对石笋微层作连续观察记录。根据高精度的石笋TIMS、ICP-MS测年数据和在显微镜下所数石笋微层数量的对比,扣除若干个沉积间断及风化层导致的微层缺失,以及显微镜下肉眼对细小微层计数的误差,我们认为,凉风洞石笋微层是年生长层的可能性较大。4,由于部分测年数据仍在测试中,目前无法精确控制石笋中沉积间断的存在导致的信息缺失,因此,我们仅仅根据部分石笋测年数据,建立了凉风洞石笋在不同时段的生长速率。全新世以来石笋的生长速率在22μm/yr-51μm/yr之间,明显高于末次冰期晚期向全新世过渡这一时间段内的石笋生长速率(16μm/yr)。这些数据间接印证了石笋生长响应于外界气候,尤其是降雨的变化。5.通过对洞穴体系的综合分析对比,我们判断凉风洞洞穴综合体系相对完整,洞穴化学沉积物的6先值较为直接的响应了土壤c压的61t值变化,即反映了地表的植被(c3植物和c;植物)的组成状况。贵州地区降雨80%集中在5-10月份,在此期间,基本受西南季风和东亚季风所控制。西南季风盛行时贵州各地的降雨频繁,是一年中雨量最集中的时期,在东亚季风影响时期,贵州多晴少雨,往往形成干早的天气。又西南季风控制区大气降雨创的值的加权平均值明显低于东亚季风控制区大气降雨δ18O值的加权平均值。因此,贵州地区年均降雨量和年均降雨δ18O值主要取决于西南(印度洋)季风的强弱:西南季风加强,降雨量增加,年均降雨剐、值偏负;西南季风减弱,降雨量减少,年均降雨δ18O值偏正。洞穴滴水的6旧O值变化基本继承了大气降水的别勿值变化。因此,对地处我国西南地区贵州南部的凉风洞,源于洞穴滴水的凉风洞石笋的别勺值变化直接响应了外界的大气降雨量的变化和西南季风与东亚季风相互的强弱交替。6.对凉风洞石笋碳、氧同位素组成的时间序列曲线作20点移动平均,发现,特别是进入全新世后,石笋的引3c值和扩、值几乎具有完全一致的同步变化,只是在变化幅度上在某些时段存在差异。说明在凉风洞石笋反映的14220-1570 aBP时间段内,尤其是10500-1570 aBP期间,本区域气候具有雨热(或干冷)同期的气候特征:在气温较高时间段,西南季风增强,气候湿润多雨,更有利于地表。植物的生长。气温降低时,随着东亚季风增强,西南季风减弱,气候干旱少雨,地表C;植物的生长占有一定的比例。据此重建和恢复了本地区14220-1570 aBP期间的古气候和古生态环境:(1).14220-10500aBP,处于末次冰期晚期,气温较低。凉风洞石笋此时段的司、值都大于-9.8‰,最小值为-9.31‰,最大值达-7.290‰,平均值为-8.552‰。说明凉风洞洞穴地表的生长植被。植物占有一定的组分,石笋的δ18C值受C3植物和C4植物的共同影响。此时段内石笋6、值也存在一定的波动(-5.651‰-6.942‰),考虑到末次冰期晚期先全新世过渡期间气温变幅较大,O'Neil等(1969)所建立的氧同位素平衡分馏方程中的温度变化已不能忽略,并且大气降雨的温度效应作用也比较明显,因此我们对此时段的季风和大气降雨量的变化不作讨论。(2). 10500-9300 aBP,新仙女木事件结束,进入全新世,气温逐渐回升。凉风洞石笋此时段的扩3c值大都小于-9.8‰,最小值为-10.377‰,最大值为-9.267‰,平均值为-9.910‰。凉风洞洞穴地表植被已逐渐由C3植物占主导。此时段石笋δ18C值明显卜降,最小值为-7.420‰,最大值为-6.077‰,平均值为-6.854‰。反映在全新世早期夏季风盛行,降雨量较大,西南季风对本地区全年降雨贡献率大。(3).9300-8300 aBP,经历一段明显温度波动变化。仟3c值在-9.8‰上下波动,最小值为-10.155‰,最大值为-9.096‰,平均值为-9.712‰。凉风洞洞穴地表植被C4植物所占比例存在反复。此时段石笋岁a0值变化幅度不是很大,最小值为-6.796‰,最大值为-6.260‰,平均值为-6.490‰。受冬季风影响,夏季风有一定的减弱,总体降雨量一般,东亚季风对本地区全年降雨贡献率比全新世初期有所增大。(4).8300-3l000BP,俗称全新世大暖期,此时段全球气温明显回升,石笋δ18C值总体逐渐降低,最小值为-n.926编,平均值为-10.496‰。凉风洞洞穴地表植被基本由C3植物所控制。但在扩飞值总体逐渐降低的趋势一F,也存在若干扩3c值明显增大时段,如7700-6700 aBP时段,61七值最大值达-8.110‰,地表C4植物所占比例已不能忽略。此时段石笋6150值变化幅度较大,最小值为-7.373‰,最大值为-5.047‰,平均值为-6.261‰。反映在全新世大暖期的大背景下西南季风和东亚季风的交替以及大气降雨量的变化存在较大的波动,说明了季风气候的不稳定性。(5).3100-1570 aBP,在3100aBP前后,凉风洞石笋的δ18C值和δ18O值均急剧上升,标志进入晚全新世。此时段气温变幅很大,δ18C值总体虽然仍偏低,平均值为-10.275‰,但刻畜介于-6.495-12.097‰之间;δ18C值平均值为-6.184‰,变幅介于-4.677-8.65‰之间,均超过以往任何时段。此时段凉风洞洞穴地表植被基本上仍然由C。植物所控制,始于3100 aBP的急速降温事件使得在全新世晚期开始时段C4植物所占比例有一定的上升。此时段内西南季风和东亚季风反复多次交替,大气降雨量存在较大幅度的变化,说明了季风气候在此时段的很不稳定性。对于169于巧70 oBP百年时间段内石笋的δ18C值和司、值巨大幅度的急剧升高,有待进一步研究,也不排除石笋表层长期裸露受外界污染所致。