云南腾冲地块北部空树河组一个菱铁矿结核中的C、O同位素变化特征     

金小赤 《地球学报》2002,23(1):37-41

空树河组是滇西腾冲地块北部的石碳－二叠纪冈瓦纳相沉积。菱铁矿结核见于该组顶部的黑色泥岩中。将一个结核通过中心切开，在切面上由中心向边缘用牙钻等间隔提取10个样品。同位素测试结果显示，δ^13C自中心向边缘逐渐由－8．09％减为－16．12％，最外一个样例外（－15．39‰），而δ^18O自中心向边缘逐渐由－10．64‰增加为0‰左右。δ^13C的变化情况表明，菱铁矿结核可能形成于硫酸盐还原带。在解释δ^18o的变化情况时，推测在结核开始生长时可能有δ^18O亏损的大气降水掺入，随着埋藏深度的逐渐加大，孔隙水的O同位素逐渐趋近正常海水的值（0‰）。  相似文献   

Study on Paleoenvironment since Late Glacial Eooch in Lanzhou Area, China     

Yang Guifang  Yin Hongfu  Li ChangAn 《中国地质大学学报(英文版)》2002,13(1)

The Hongzuisi Section in Lanzhou area is used to infer the paleoclimate since the late glacial epoch. Through combined analysis of organic carbon isotope and CaCO3 content, paleoenvironment evolution of Hongzuisi Section since the late glacial epoch is discussed. There were changes in both drymoist and warm-cold. Especially the climate changes can be compared with synchronous sections of other areas, which provides useful information for our future forecast.  相似文献   

近20年海南岛森林生态系统碳储量变化   总被引：49，自引：2，他引：49  

曹军  张镱锂  刘燕华 《地理研究》2002,21(5):551-560

热带森林在碳循环研究中有重要作用。根据目前森林碳储量的计算方法和海南森林资源二类调查数据 ,估算了不同时段的碳储量 ,并分析其动态变化特点。结果表明 :海南森林碳储量从 1979年的 30 4 5TgC增加到 1998年的 37 74TgC ,年均增加 0 36 4 5TgC ,增长率为1 19% ,是全国平均增长率的 2 5倍 ;海南森林在碳循环中起不断增强的碳汇作用 ;森林碳密度呈加速减少趋势 ,储碳潜力将很大 ;随着海南全面禁止采伐和封育等林业措施的实施 ,森林面积扩大 ,林龄结构改善 ,储碳能力将进一步提高 ,海南森林在全国或全球碳循环中的作用和社会价值与意义将日渐突出。通过对碳储量计算不确定性的分析和讨论 ,提出应加强对森林群落各层次生物量的实测与实地监测研究 ,统一计算方法 ,以提高碳储量计算的精度  相似文献   

Research progress of socio-economic water cycle in China   总被引：3，自引：0，他引：3  

Jia Shao-feng  Wang Guo  Zhang Shi-feng  Yu Gui-rui  Wang Jin-xia  Xia Jun 《地理学报(英文版)》2002,12(1):114-120

China has made great progress in the study of socio-economic water cycle. She has completed national water resources appraisement and medium to long-term water supply planning. She has been engaging in study on water-deficient regions in North China and Northwest China for about half a century. For solving water shortage problem in northern China, she has put forward the famous South-to-North Water Transferring Projects, which has been set as one of the four biggest national projects in the Tenth Five-Year-Plan period although there are still debates. For promoting water use efficiency, China has been reforming her water management system, including water right system and water price system. There has already been a case of water right purchase. China has also done a lot of research on the interaction between human activity, water and ecosystem. For meeting the need of sustainability and coordinating water resources development and environmental protection, the study of ecological water requirement became very hot in recent years. There are three focuses of socio-economic water cycle study now in China: water transfer projects from the south to the north, water resources management and ecological water requirement.  相似文献   

Sedimentary cycles of trace elements in Salawusu River Valley since 150 ka BP   总被引：6，自引：0，他引：6  

Yao Chun-xial  Li Bao-sheng  Jin He-ling  David Dian Zhang  Yan Man-cun  Zhu Yi-zhi  Li Hou-xin  Zhang Yu-hong  Luo Kai-li 《地理学报(英文版)》2002,12(1):65-71

The paper makes some analyses on 11 trace elements in the Milanggouwan stratigraphical section in the Salawusu River valley, which is regarded as a prototype geology-palaeoclimate record since 150 ka BP. The results show that the content and variation of trace elements has experienced remarkably regular changes in the pace with coarse and fine sedimentary cycles of palaeo-aeolian sands to its overlying fluvio-lacustrine facies or/and palaeosols. The trace elements with chemical properties of relatively active (V, Sr, Cu, Ni, As) and relatively stable (P, Pb, Rb, Mn, Nb, Zr) are a manifestation of the corresponding 27 changeable cycles between peak and valley values, appearing a multi-fiuctuational process line of relative gathering and migration since then. The low numerical value distribution of these two types of trace elements in the aeolian sand facies represents erosion and accumulation under wind force during the cold-dry climate. Whereas their enrichments in both fluvio-lacustrine facies and palaeosols are related to the valley’s special low-lying physiognomic position between the Ordos Plateau and the Loess Plateau under the warm and humid climate conditions. The above relatively migrated and gathered change of the trace elements is the result of 27 climatic cycles of cold-dry and warm-humid, which is probably caused by repeated alternations of winter monsoon and summer monsoon in the Mu Us Sandy Land influenced by the climate vicissitudes in northern hemisphere during glacial and interglacial periods since 150 ka BP.  相似文献   

Upper Oligocene-Lower Miocene shallowing-upwardlacustrine sequences controlled by periodic and non-periodic processes(Ebro Basin, northeastern Spain)     

Arantxa Luzón  Angel González  Arsenio Muñoz  Belén Sánchez-Valverde 《Journal of Paleolimnology》2002,28(4):441-456

The lacustrine facies from two sections (Candasnos and Fraga) ofthe Oligocene-Miocene Torrente de Cinca lithostratigraphic Unit in thecentral part of the Ebro Basin (Spain) have been analysed to determine theinfluence of orbital parameters in lacustrine sedimentation. The unit ispredominantly composed of limestones and marls, and represents a shallowlacustrine freshwater system. The sedimentological features of the faciesstudied demonstrate that the lower part of the Candasnos section representsoffshore lacustrine subenvironments whereas the upper part, and the whole ofthe Fraga section, characterise marginal lacustrine areas. Series of stratalthickness variations of limestone, marl, and limestone/marl couplets fromboth sections have been analysed using spectral analysis. This shows thatinformation corresponding to periodic cycles only appears in the offshorefacies, that is to say, in the lower part of Candasnos section, and disappearsin the marginal facies where non-periodic cycles exist. Furthermore, thespectral analysis of the offshore facies highlights the existence of a peak inthe power spectrum with a period of around 7 (6.8 to 7.8) that can berecognised in the field as shallowing-upward lacustrine sequences.Magnetostratigraphic data from the Candasnos section allow us to establish atime span of 2,808 years for the limestone/marl couplet from the lower partof this section, and between 19,000 and 22,000 years for the periodic cycleidentified, thus representing the climatic precession cycle. Shallowingsequences from marginal areas do not correspond with any periodiccycle.  相似文献   

Floodplain–river ecosystems: lateral connections and the implications of human interference     

Martin C. Thoms   《Geomorphology》2003,56(3-4):335

Floodplains are ecotones that form a transition between aquatic and terrestrial environments. These important ecosystems can be described as dynamic spatial mosaics in which water plays an important role in connecting various patches on the floodplain surface. Hydrological connections facilitate the exchange of carbon and nutrients between the river channel and the floodplain and therefore influence the productivity of the entire river system. This paper examines the influence of hydrological connections on the potential exchange of dissolved organic carbon between a large Australian floodplain to a river channel, and the effects of land and water developments on these exchanges. The paper proposes that an understanding of floodplain ecosystems requires an interdisciplinary approach—a recognition of the importance of the three disciplines hydrology, geomorphology and ecology. Large-scale water-resources and floodplain development has significantly altered the spatial and temporal patterns of hydrological characteristics in the Lower Balonne floodplain, Australia. The magnitude, frequency and duration of flooding events have all been reduced. The construction of levees and water storages has also reduced the reactive floodplain surface area. The presented data show the impacts of these changes on the potential supply of dissolved organic carbon from the floodplain surface during periods of inundation. Annual reductions of up to 1293 tonnes of dissolved organic carbon supply were noted and reductions were especially significant for floods with an average recurrence interval of 2 years or less. Some small flood events no longer facilitate the potential supply of dissolved organic carbon from the floodplain to the river channel because of water-resources and floodplain developments.  相似文献   

油气化探中甲烷碳同位素应用、存在问题与对策研究   总被引：5，自引：2，他引：5  

黎绍杰 《矿产与地质》2003,17(1):54-58

阐述了在地表油气化探实践当中甲烷碳同位素对地表土壤烃气成因判别的有效性，但有时也会遇到判断错误的情况。通过对应用实例的分析，指出因忽略了土壤中异常甲烷是一种混合成因甲烷，从而导致判断失误。为全面解决这一问题，提出了同时选送数量相当的背景土壤样品和异常样品进行甲烷同位素测定，然后通过教学方法计算出真实反映来源于油气藏中的甲烷的碳同位素值的对策方案。  相似文献   

浙江天台地区赖家组的划分与分布   总被引：12，自引：0，他引：12  

方晓思程政武  蒋严根杨良锋 《地质通报》2003,22(1):21-27

柴达木盆地是中国目前保存较为完整的、连续的、巨厚的河－湖相沉积记录的盆地，通过对ZK701＋801，水6孔，涩中6和涩深1井等典型剖面孢子花粉组合特征和分布规律的研究，详细地论述了第四纪孢粉组合带及其所代表的植被，气候演变进程，自1．87MaB.P.以来共识出了59个孢粉组合带，划分出29个完整的冷暖气候旋回，并且同中国西北第四纪黄土－古土壤系列的37个气候旋回以及深海钻孔氧同位素气候旋回进行了较好的对比。  相似文献   

Geochemical Characteristics of Gold Polymetallic Deposits as Exemplified by the Laozuoshan Deposit,Heilong jiang,China     

代立东  李和平  王思源  魏俊浩 《中国地球化学学报》2003,22(1):89-96

From the studies of ore deposit geologic settings,sulfur isotopes,lead isotopes,carbon isotopes and oxygen isotopes,fluid inclusions and petrochemistry in this paper,the authors have drawn a conclusion that the ore-forming hydrothermal solutions are the high-temperature magmatic hydrothermal solutions for the gold ore deposit,and at the same time,the involvemety of crustal materials can not be ruled out .It is the first time that the authors have proposed that the Laozuoshan gold-ploymetallic ore deposit in Heilongjiang Province was formed in the calc-alkaline series environment at the margin of an active continent.  相似文献