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    2009, Volume 16 Issue 5
    10 September 2009
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     Sedimentary record and Cretaceous Earth Surface System changes.
    WANG ChengShan CAO Ke HUANG YongJian
    2009, 16(5): 1. 
    Abstract ( 1852 )   PDF (2538KB) ( 1228 )  

    The Earth Surface System is a complicated system which includes geosphere, atmosphere, hydrosphere and biosphere. The Cretaceous is a fantastic research example, when some important events occurred in the Earth Surface System. During the Late Cretaceous, the huge mantle plume brought ocean floor accelerated spreading and it caused the formation of many oceanic plateaus. At the same time, the South and North Atlantic became connected. A new gateway which may take an important role in ocean cycling was formed. The volume increasing elevated the sea level 200300 m higher than today, and massive transgression reached its maximum during the midLate Cretaceous. In this process, volcanic activity and increased land surface eroding provide a large number of nutritious elements for ocean. They made a worldwide alimental and anoxic ocean environment. The releasing carbon dioxide led to a “greenhouse climate”, of which the paleotemperature reached a high level (about 10 ℃ higher than today). CORB (Cretaceous Ocean Red Beds) is a newly introduced geological event, and it has been accepted by scientists from different countries. After more than twenty years research, it has been defined as a group of red, pink and/or brown finegrained pelagic marine sedimentary deposits in oxidized, oligotrophic and low production environments. These events in the Earth Surface System coupled each other in the form of energy cycling including element (e.g. C, S, P, H, O etc.) cycling. And they drove the Earth Surface System to change more actively. But a prevalent conclusion of the change mechanism has not been reached yet because of less Cretaceous continental sedimentary research. The wide distributed Cretaceous continental sedimentary record in China and the accomplishment of the project of “Cretaceous Scientific Drilling” provided the advantage of material for the research. They are the keys to the study of Cretaceous Earth Surface System.

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    On the Cenozoic climate changes and greenhouse gases.
    ZHOU Xin, GUO Zheng-Tang
    2009, 16(5): 15. 
    Abstract ( 1659 )   PDF (2102KB) ( 1100 )  

    Abstract:  Based on the available data, earlier studies and our own recent results, in this paper we discuss the potential links between the Cenozoic climate changes and the atmospheric concentrations of greenhouse gases at the tectonic, orbital and millennial timescales with special emphasis given to CO2. The comparisons show a generally coupling between them, indicating that the greenhouse gases are among the most prominent driving forces of the climate system. However, a significant amount of decoupled aspects is also clear. These include the longterm global cooling and ice volume increase during the Neogene under relatively stable CO2 concentrations, the strong asymmetry of hemispheric climates at the glacialinterglacial scale during the midPleistocene, and the seesaw pattern between the Southern and Northern Hemispheres at millennial scales. Also, most of the studies showed that the  change in the CO2 concentration at the orbital and millennial scales lagged the change of the global temperature, which suggested that the changes in the CO2 concentration at these timescales were likely induced by climate changes, but may have a significant feedback of CO2 to climate conditions in modulating the amplitudes of climate changes. The climateCO2 relationships during the Cenozoic are helpful for understanding the mechanisms of the ongoing global warming, but the differences in the boundary conditions between the geological past and the presentday must be taken into consideration. Climate and greenhouse gases may be, to some extent, a selfmodulated system while little is known about the relevant processes. Datamodel comparisons would be of great value towards understanding these links.

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    Constraints of sedimentary records on Cretaceous paleoclimate simulation in China mainland
    CAO Ke WANG Meng
    2009, 16(5): 29. 
    Abstract ( 1549 )   PDF (1310KB) ( 941 )  

    Abstract:  Simulation has been an important method in research on Cretaceous paleoclimate, but some boundary conditions have not been confirmed yet. In this study, we have constrained the distribution of land and ocean and the paleotopography in the Cretaceous using continental sedimentary records in China. During the Early Cretaceous, the Karakorum Gulf lay in the southwest of Xinjiang and the Wusuli Gulf was located to the east of Songliao Basin, Northeast China. During the Late Cretaceous, the global sea level rose, which made the Tethyan Ocean extend northward; the southwest Tarim Gulf and Karakorum Gulf lay in the west of Xinjiang; and the Wusuli Gulf had retreated from Northeast China. In the aspect of paleotopography, the Da Hinggan Mountains, Tianshan Mountains, Qilian Mountains, Kunlun Mountains, Hengduan Mountains, QinlingDabie Mountains, West Sichuan Plateau, and Yungui Plateau had already existed and may have reached some altitude. It is pointed out that the existence of East Plateau and Southeast Ridge would have been of significant influence on Cretaceous climate conditions in China. Furthermore, we have discussed the significance of making validation and comparison between paleoclimate simulation and sedimentary records in reconstruction of Cretaceous paleoclimate.

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    The biotic and environmental response to the geological events on the Earth during the Late Mesozoic.
    LIU Yong-Qing KUANG Gong-Wei JI Shu-An LV Jun-Chang LIU Yan-Hua JIANG Xiao-Jun BANG Nan
    2009, 16(5): 37. 
    Abstract ( 2614 )   PDF (2391KB) ( 1091 )  

     Three terrestrial biotas, i.e., the Yanliao, Jehol and Fuxin biotas, existed around the North China during the Late Mesozoic. Evolutionary radiation of the biotas accompanied with a series of geological events, such as lithospheric thinning, magmatic activities, metamorphic core complex and extensional basins, which suggests a mechanism of interaction and response in the Earth surface systems. Radiation and extinction of the biotas were highly coincident with large igneous provinces (Tiaojishan Fm.Zhangjiakou Fm. and Dabeigou Fm.Yixian Fm.) in geochronological perspectives. Ecosystems and palaeogeography of the Earth surface system were strongly, directly or indirectly, affected or reformed by those contemporaneous geological events, and for surviving the biotas had to change themselves and to radiate to adapt the affected ecosystems or palaeogeography. Ecosystems or evolutionary radiation was also affected by volcanic eruptions and magmatic activities. The biota (fossils) are mostly preserved in lacustrine deposits bearing a number of volcanic tuffs or interclations of lavas, which provide a window for understanding the interaction and response. A remarkable geological event and a response to global Earth surface system, i.e., the North China Cratonbreakingup, occurred during the Late Mesozoic, which was recorded within the contemporaneous sedimentary successions and a series of characterized terrestrial deposits. Synthesized researches on biotic evolution, alternation and accurate chronological dating, taphonomy of vertebrate or invertebrate fossils and elemental or isotopic geochemistry of bones of fossils and sediments, i.e., HBCNOS and COSr, could help us to well understand the biotic and environmental response to the geological events on the Earth surface system and reconstructed the palaeogeography, palaeoecologic environment and palaeoecosystem of the Late Mesozoic, North China.

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    Distribution characteristics and climate significance of continental special deposits in the Early Cretaceous.
    XIANG Fang SONG Jian-Chun LUO Lai TIAN Xin
    2009, 16(5): 48. 
    Abstract ( 6804 )   PDF (2371KB) ( 10681 )  

     By systemically summarizing geological data, we have identified the following types of continental special deposits that may indicate the climate characteristics, namely, the calcareous deposit, flammable organic rock, evaporite, desert sedimentary system, lateritic weathering crust, ferruginous deposit, copperbearing deposit, volcanic deposit, limestone, dolostone, and bentonite. On the basis of distribution maps of 6 periods of the Early Cretaceous, we are able to discuss the temporal and spatial distribution characteristics of different special deposits. Combined with climate significance of continental special deposits, we summarized the climate indexes as follows: the flammable organic rock, the pyrite and siderite associated with black shale, and the bentonite reflect warm and humid climate; the lateritic weathering crust and ferric deposit reflect humid and hothot climate; the gypsum and limestone reflect warm and dry climate; the rock salt, glauberite, desert sedimentary system and dolostone reflect hot and dry climate; the volcanic deposits reflect high temperature climate; the calcareous deposit and copperbearing deposit reflect aridsemiarid climate. On the basis of distribution and assembly characteristics of special deposits, six climate types can be classified: (1)warm and humid climate; (2)warm and humidwarm and dry climate; (3)warm and dry climate; (4)hot and dryarid climate; (5)hot and drywarm and dry climate; (6)hot and dry climate. The distribution of different climate areas was latitudinal zoning from the Berriasian to the Barremian. The distribution manner changed to the overlapping of latitudinal distribution with meridional distribution in the Aptian and the Albian, and at the same time, the types of climate area increased in the East. The climate was hottest and driest in the Hauterivian and was most humid in the Albian.

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    Paleosols of the midCretaceous: A report from Zhejiang and Fujian, SE China.
    LI Xiang-Hui CHEN Shi-Dun CAO Ke CHEN Yun-Hua XU Bao-Liang JI Yan-Na
    2009, 16(5): 63. 
    Abstract ( 2111 )   PDF (2466KB) ( 1051 )  

     An investigation on the midCretaceous continental sediments was recently executed in both SW Zhejiang and SW Fujian provinces, SE China. It is the first time to report the Cretaceous paleosols in mainland China. Three types of paleosol are recognized as argillisol, calcisol, and oxisol based on the observation of eleven cross sections in field. The argillisol horizon is characterized by burrows and root traces within reddish (silty) mudrock, the calcisol is marked by calcareous concretion within pale purple calcareous mudrock, and the oxisol is the association of ferric tegument and concretion within reddish purple, grayish orange siltstone and mudrock. According to climate direction of paleosol type, it is proposed that it could have been in aridity or semiaridity of subtropic during the AptianAlbian epoch of the midCretaceous in SW Zhejiang, where the calcisol was recorded in the Hengshan Formation, Zhongdai Formation, Jinhua Formation, Guantou Formation, and Chaochuan Formation; and at the same time, it was in semiaridity of tropic in SW Fujian indicated by oxisol within the Bantou Formation, Junkou Formation, and Shaxian Formation. In the Cenomanian, it could have become more moisture in SW Zhejiang evidenced by the production of the argillisol within the Quxian Formation, whereas the paleoclimate in SW Fujian in the Cenomanian might have been similar to that in the AptianAlbian even if the sediments were changed as huge conglomerates (socalled “Danxia Landorm”) by tectonism.

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     Climate significance of continental special deposits.
    TIAN Xin XIANG Fang LUO Lai SONG Jian-Chun
    2009, 16(5): 71-78. 
    Abstract ( 1858 )   PDF (1026KB) ( 1359 )  

    The continental special deposits were formed on the surface of the geosphere, hydrosphere, atmosphere and biosphere, which are more effective than marine strata in recording the information of the earth surface environment. By the research of the clay mineral and climatic index of the sediment in the sedimentary rock and its temperature measured by oxygen isotope, we can get different climate information. On the basis of these research methods, we can extract from continental special deposits, such as continental red beds, desert sedimentary systems, evaporates, coal and oil shale etc., some rich climate information as the following: the desert sedimentary systems represent hotarid climate; the appearance of the continental red beds reflects the high temperature and oxidized environment, which can formed in both arid and humid tropical climate; the mirabilite implies the climatic conditions being arid and cold; the gypsum stands for hotarid, high water salinity and strong evaporation condition; the coal and oil shale generally gathered in the environment with warm and humid climate. These researches on the special deposits can be used to reconstruct paleoclimatic and continental paleoenvironment.

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    Microstructures of one species of Quercus from the Neogene in Eastern Zhejiang and its palaeoenvironmental indication.
    GU Hui SUN Bai-Nian LI Xiang-Chuan XIAO Liang TUN Jing-Yu
    2009, 16(5): 79-90. 
    Abstract ( 1852 )   PDF (2662KB) ( 658 )  

     The fossil Quercus aff. delavayi Franch was collected from the Xiananshan Formation of the Miocene in Tiantai, Zhejiang Province, which is the same as extant Quercus delavayi Franch not only in the leaf architecture, but also in the epidermal characteristics. Macro and microcharacteristics show that present fossil material is related to extant Q. delavayi. By comparing microstructure of extant Q. delavayi growing in different regions and different years, it is found that the ontogeny of trichome base of Q. delavayi is a recapitulation to the phylogenetic development of trichome base of the subgenus Cyclobalanopsis. The comparison of cuticular characteristics between fossil and extant Q. delavayi based on the principle of the Nearest Living Relative species suggests that (1) atmospheric CO2 concentration in Miocene was about 39522±561ppmv; and that (2) the Miocene climate of Tiantai, Zhejiang was warmer and more humid than today.

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    High resolution rapid climate change records of lacustrine deposits of Diexi Basin in the eastern margin of QinghaiTibet Plateau, 4030 ka BP.
    ZHANG Yan SHU Li-Dong YANG Wen-Guang LUO Gong JIANG Lin HE Da-Fang LIU Juan
    2009, 16(5): 91-98. 
    Abstract ( 1781 )   PDF (1482KB) ( 866 )  

    The deposition of Diexi ancient barrier lake in the upper reaches of Minjiang River was redated by AMS14C dating, and the result shows it started at 405 ka BP. The grainsize proxy index can reflect the precipitation and thus the climate drywet change. In addition, the obvious comparability between the mean grainsize curve of Diexi Section lacustrine deposits and the δ18O of Greenland ice core and Nanjing Hulu Cave stalagmites shows that the grainsize proxy index could respond to the global climate change, and reflect the chilling and warming. Thus the paleoclimate evolution in the studied area could be divided into three stages: 405334 ka BP, cold and dry; 334317 ka BP, warm and humid; 317311 ka BP, warm and humid, but not as much as the previous stage. The differences between these curves could be interpreted by the variation in location, insolation and monsoon.

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    Changes in climate and vegetation in Niangziguan Spring Watershed of Shanxi Province since MIS12/11 recorded by the spring tufa.
    LIU Zai-Hua SUN Hai-Long ZHANG Jin-Liu
    2009, 16(5): 99. 
    Abstract ( 1593 )   PDF (1581KB) ( 1084 )  

     High precision 230Thdating of the tufas deposited on different terraces of Mian River at Niangziguan shows that the ages of the oldest tufas on the terrace II are between ~406 ka and ~466 ka, which are much higher than those dated by the thermoluminescence method earlier, indicating that the tufas on the terrace II deposited during the Marine Isotope Stage (MIS) 12/11 of the middle Pleistocene but not in the late Pleistocene as suggested in early studiesIt was inferred that the tufas on the terrace III of Mian River deposited earlier, possibly during the MIS 14/13 of the middle PleistoceneThe 230Thdating of the top tufa on the terrace I shows that the tufa deposited 5 ka ago, i.e., before the middle HoloceneCombined dimensions of tufa deposits with their carbon and oxygen isotopic compositions (δ13C, δ18O), it shows that all the tufas on the terraces of Mian River were formed mainly under hot and humid climateHowever, from the time when the tufa on the terrace II was formed till now, the tendency of climate change was towards drier and colder, and the vegetation in Nangziguan spring watershed degraded gradually

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    A simple analysis of influential factors for Cretaceous marine organicrich sediments in Southern Tibet.
    WANG Li-Cheng WANG Cheng-Shan LI E-Lin WEI Yu-Shuai
    2009, 16(5): 107. 
    Abstract ( 1735 )   PDF (1563KB) ( 1466 )  

     A marine Cretaceous organicrich sequence deposited extensively in Southern Tibet, and the black shale therein correlated with CenomanianTuronian Anoxic Events has been receiving extensive interest. However, the TOC content is much lower than the black shale in West Tethys. Therefore, understanding the dominated mechanism of the organicrich sediments is important to the problem. We selected 4 cross sections in  Southern Tibet,which have been studied more intensively by the predecessors, namely, the Gamba ZongshanⅡ, the Tingri Gongzha, the Gyangze Jiabula and the Chuangde, to calculate the sedimentation rate, accumulation rate and paleoproductivity by using related data. The result showed that the highest sedimentation rate occurred at CenomanianTuronian, and the Gamba, Tingri and Gyangze areas had different sedimentation rate owing to their different deposited environments. Moreover, when the sedimentation rate <4 cm/ka, the content of TOC will increase with the increasing sedimentation rate; but there is no obvious correlation at the higher sedimentation rate. The primary paleoproductivity in Gyangze is lower, and the formation of the black shale is not the result of high paleoproductivity; it may be related to anoxia.  Although calculated paleoproductivity in Gamba and Tingri is also lower, the excursion of carbon isotope and speculated coastal upwelling indicates that the Cretaceous organicrich sediments had high primary paleoproductivity. The condition of paleooceanography e.g. high paleoproductivity and anoxia, which is excellent for the deposition of organicrich sediments, existed in Gamba and Tingri area. The interplay of these two factors together with the sedimentary rate controlled the deposition of the organicrich sediments. The cause of low TOC content and  thus of low calculated paleoproductivity was the intensive weathering at the late stage of diagenesis.

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     The C and O isotopic compositions and their evolution recorded in the carbonate interval of the Yanshan area from 16 to 10 Ga, and their geological implications.
    KUANG Gong-Wei LI Jia-Hua BANG Nan LUO Shun-She CEN Chao
    2009, 16(5): 118. 
    Abstract ( 2027 )   PDF (2456KB) ( 790 )  

      Based on the C and O isotopic profile of 114 analytic results obtained by the standard method of phosphorolysis, we have discussed the compositions and evolution of δ13C and δ18O recorded in the carbonates in the Yanshan area during the interval of 16 10 Ga and their geological implications. The C and O isotopic profile reveals a secular cyclic evolutionary trend in ascending order of carbonates, i.e., δ13C shows a shift from -3‰ to +30‰ and δ18O shows a range from -20‰ to -80‰. An elevation of δ13C correlated with the relative variation from intertidal to subtidal sedimentary environments, the sea level rising, the flux of fresh water and the high organic productivity, whereas a decreasing shift corresponded to a transition from supratidal to intertidal facies or sedimentary boundaries in term of sequence stratigraphy. The nodular limestone or shalestone has negative δ13C excursion, representing the maximum sea flooding sediments from Gaoyuzhuang and Hongshuizhuang Formations respectively. The O isotopic composition and evolution suggests that a salted water paleoenvironment was prevailing over the research area during the synsedimentary period from the Upper Yangzhuang to Lower Wumishan Formations, i.e., the more salted interval, which recovered later in Upper Wumishan Formation. The current study and C and O isotope evolution are consistent with the previous research results, which provides isotopic evidence supporting the existence of an aulacogen basin alone, and furthermore are highly concordant with the C and O isotope evolutions in Belt Supergroup in North America and MidRiphean in Ural, Russia, which suggests a response to a global paleoocean geochemical setting.

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    Cyclostratigraphic study of the Upper Cretaceous of Southern Tibet, China: A case study of Gongzha section.
    MA Chao WANG Cheng-Shan CHEN Xi HUANG Yong-Jian
    2009, 16(5): 134. 
    Abstract ( 1478 )   PDF (1671KB) ( 1355 )  

     The Cyclostratigraphic study has become a principal tool for refinement of the geologic time scale. Compared to the Western Tethys, the Cyclostratigraphic study on the Eastern Tethys is relatively insufficient. The precision of the study for the preQuaternary still needs to be advanced in Eastern Tethys. Cretaceous marine sediments are cropped out widely in Southern Tibet, among them the late Cretaceous in the Gongzha section of Tingri Area is rather continuous and  integrated. Based on the field observation and the measurement of the bundle thickness, we have analyzed the cycles of the orbital parameters with Fast Fourier Transport (FFT)  in this paper. And the result well matches the theoretical value as that the cycles of the precession are 4092 ka (E1),1279 ka (E2),and 93 ka (E5), and the cycles of the eccentricity are 512 ka (O1),409 ka (O2),and 389 ka (O2). In the process of power spectral analyses, a tuning treat based on the relationship between bundle and superbundle set was conducted, and those results  before and after the tuning were compared to confirm the significance of the tuning. Moreover, the variety of sedimentation rate was confirmed as well.  Generally, the sedimentation rate is in the range of 086253 cm/ka, which increased from the bottom to the top of the strata. In addition, the result of this study is compared with the published results of Cretaceous marine sediments in Western Tethys and  those from  other areas in  different ages, which indicates that in Eastern and Western Tethys, the shape, genesis and the cycles of the orbital parameters of Cretaceous marine strata are similar. And the conclusion that the orbital cycles  becoming longer are well consistent  with the theoretical value. Finally, a suggestion for further  research is given.

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    Geobiological setting of the marine organic carbonrich accumulation in midCretaceous.
    GU Jian-Zhong MO Xiao-Qiao ZHANG Yi-Yi DIAO Jing
    2009, 16(5): 143-152. 
    Abstract ( 1831 )   PDF (1810KB) ( 926 )  

     The midCretaceous (~12588 Ma) is characterized by a remarkable increase of global organic matter (OM) accumulations—the significant source rock of many large oil fields in most oceanic basins. Based on the previous discussion about geological setting and major controlling factors on the marine organic carbonrich accumulation, this paper proposes that both high primary productivity (PP) and oceanic anoxic events (OAE) controlled the wide distribution of marine organic carbonrich sediments in the midCretaceous. In fact, OAE not only sped up the extinction and the replacement of marine life, causing  huge amounts of OM accumulation, but also promoted the regeneration of nutrients (e.g. P, N, Fe) and the flourish of anaerobic autotrophic microorganisms (e.g. green sulfur bacteria, cyanobacteria, archaea) as well. The high PP in turn exacerbated the oceanic anoxia. During that period, the Cretaceous large igneous events triggered the sustaining greenhouse climate and abnormal oceanic environments together with euxinic conditions, confusion currents and weak upwelling, which led to the improved productivity and OAE, and eventually, caused the extensive accumulation of organic matter.

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    The deeptime research by chromatometry: An example from the Cenomanian to Turonian Stages of the Cretaceous, Gongza section, Southern Tibet.
    LI Lin ZHOU Ti-Jiang HUANG Yong-Jian MA Chao
    2009, 16(5): 153-159. 
    Abstract ( 1941 )   PDF (1456KB) ( 701 )  

     Chromatic methods have been well used in paleoclimate research for unconsolidated or semiconsolidated sediments. However, few researches based on these methods have been reported from diagenetic rocks, since their primary compositions and colors may be altered in the process of diagenesis and postdiagenesis. Thus, the deeptime research by means of chromatometry is still open to question. Ninetyeight Cretaceous rock samples collected from the Gongza Section, Tingri, southern Tibet, were studied using chromatic methods, together with microscopic observations and major elements analysis. Main conclusions were drawn as follows. (1) In the CIE1976 L* a* b* color space, the variation trends of L* and a*, with mirror symmetry, indicate two main semiperiods of 92 m and 18 m obtained by Fast  Fourier Transformation; while L* and b* values show similar variation trends. (2) Correlation analysis between chromatic indices and major elements suggests that L* value has a positive correlation with the content of carbonate, b* value is mainly influenced by manganese content, and together they can put some constraints on the chemical change of paleoocean; whereas a* value is largely controlled by the content of clay minerals, which reflects paleoclimatic changes.

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     Nd isotope evolution of ocean waters and implications for paleoocean circulation.
    DIAO Kui-Dong JIANG Shao-Chong ZHENG Xin-Yuan CHEN Tian-Yu LING Hong-Fei
    2009, 16(5): 159-171. 
    Abstract ( 2172 )   PDF (1489KB) ( 1168 )  

    Nd isotope of ocean waters has become an important tracer for continental weathering and oceanic circulation. Dissolved oceanic Nd is controlled by input from continental weathering, while hydrothermal input can be ignored. The Nd isotope composition of seawater is not uniform in the presentday oceans because the oceanic residence time (5001000 a) of Nd is shorter than the mixing time (~1500 a) of the ocean and the relative contributions of Nd from ancient continental versus young volcanogenic materials differ in  various basins. Therefore, the Nd isotope system has been used as a tracer for water exchange and paleoocean circulation. There are four major marine materials which can preserve Nd isotope compositions of paleoocean waters: hydrogenetic ferromanganese crusts, planktonic or benthic foraminifera, fossil fish teeth or bones, authigenic FeMn oxide fraction in marine sediments. Each material has its own advantages and disadvantages. Cenozoic Nd isotopic evolutions of major oceans on timescales of millions have been acquired by analyzing FeMn crusts. High resolution Nd isotopic evolution can be acquired through studying foraminifera, fossil fish debris and FeMn oxides.According to Nd isotopic evolution we may reconstitute the  water exchange to trace open and closure of paleoseaways, which can be used to study the relationship between tectonic activities and climate changes. The combination of  Nd isotope and the proxies for climate change can be used to study the relationship between ocean circulation and climate shifts. Nd isotope of surface water can provide information about continental weathering input.

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     Progress of the study of reactive iron cycling in the paleoocean and its applications to the genesis of Cretaceous anoxicoxic sedimentary transition.
    HUANG Yong-Jian WANG Cheng-Shan
    2009, 16(5): 172-180. 
    Abstract ( 1548 )   PDF (1247KB) ( 1730 )  

    Iron, as one of the most abundant elements in the Earth crust, cycles within a series of geochemical processes. The iron in the modern ocean mostly comes from riverine, glacial and aeolian by the input of iron oxide particles and dissolved iron ions. The iron oxides will change their form and finally be buried during the early diagenetic process characterized by the burial and degradation of organic matter, which is called the reactive iron cycling. Iron oxides would continue to be formed or at least not to be dissolved under oxic conditions, and the sediments in brown to red color will then be dominant. While in a reducing environment, iron oxides will be dissolved, with the possible migration of iron ion in the ocean, and then buried as siderite, pyrite, or other ironbearing minerals. A series of iron proxies have been suggested to distinguish the redox condition of the paleoocean, by studying iron cycling in the modern ocean. On the basis of this methodology, scientists have reconstructed the redox history of paleoocean since the Archaean as a sequential appearance of the ferrous, sulfidic and oxic ocean. Owing to the adsorption of phosphorus onto the iron oxides, and the inability of reducing ironbearing minerals to combine with the phosphate ion, more phosphorus will be buried in the sediments under oxidized conditions; while a reducing environment will enhance the release of phosphorus from the sediments. Because the phosphorus is the constraining element for the marine production, the ocean will become more productive under reducing conditions; but less organic matter will be produced under moreoxic environment. Such feedback mechanism has been preliminarily proved in the deposition of Cretaceous anoxic and moreoxic sediments. But more works are still needed to elucidate the contribution of different forms of iron burial to the occurrence of such special sediments.

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    Geochemical research on the Late Cretaceous strata of Well SK1 in Songliao Basin.
    FENG Zi-Hui HE Qiu-Li WANG Xue FANG Wei SONG Zhi-Guang
    2009, 16(5): 181-191. 
    Abstract ( 2396 )   PDF (2057KB) ( 773 )  

    Well SK1 is the first whole coring hole of the Cretaceous strata in China for scientific research. Different layers of shale in the Well SK1 (scientific well) in the Songliao Basin were systematically analyzed by geochemical technique to determine the profile of total organic carbon content (TOC), maturity and depositional environment. The results show that the most organicrich source rock is the Qingshankou 1st (K2qn1) formation with an average of TOC at 321% while most greater than 2%. Qingshankou 2nd3rd (K2qn2+3) formations, Yaojia member (K2y) and Nenjiang 1st2nd (K2n1+2) formations have subordinate content of organic carbon. The vertical distribution of TOC shows nine HTB (high TOC at the base, decreasing upward) units, indicating the cyclicity of climate, biomass productivity and organic preservation. The shales of Qingshankou 1st formation mainly contain lacustrine typeI kerogen and have higher content of steranes, indicating algae as the main organic input. The higher amount of gammacerane, relatively low value of Pr/Ph (pristane vs. phytane) and presence of dinosterane all suggest that the lake during the period of Qingshankou 1st formation deposition was subjected to salinity stratification, strong reducing deposition environment, and the potential marine transgression. The shales of Qingshankou 2nd3rd formations mainly contain typeI and typeII kerogens. Multi indices such as gammacerane index and the value of Pr/Ph indicate that the fluctuating lake and the organic carbon contents must have been mixed with more terrestrial organic debris during the period of Qingshankou 2nd3rd formations deposition. The kerogen types of Yaojia member vary widely, from typeI to type III. It is a general truth that shale with higher organic carbon content will be more oilprone, and sections with organicrich shale in Yaojia member are believed to have promising oil potential. Multi geochemical indices indicate that the deposition environment varied quickly during the deposition of Yaojia member. The shales of Nenjiang 1st2nd (K2n1+2) formations are dominated by typeI and typeII kerogens and the amount of 4methysterane may be attributed to dinoflagellate. The relatively higher amount of gammacerane and low value of Pr/Ph indicate the salinity stratification of water column during the deposition of Nenjiang 1st2nd formations deposition. The source rock of Qingshankou 2nd3rd formations became mature in the middepth with peak oilgeneration at 1500 m.

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    Filling types of terrestrial basin and their control on the formation of hydrocarbon source rocks: Taking Songliao Basin as an example.
    WANG Xiao-Fu WANG Cheng-Shan FENG Zi-Hui ZHANG Shun HUANG Qing-Hua HUANG Yong-Jian
    2009, 16(5): 192-200. 
    Abstract ( 2644 )   PDF (1503KB) ( 1120 )  

     This article introduces the theory of lakebasin filling type classification, which was proposed by Bohacs. and Carroll. They had summarized many lakebasin lithofacies, and differentiated them into three typical associations: fluviallacustrine, fluctuating profundal and evaporative. Corresponding to these three lithofacies associations, we also differentiated the lakebasin into three filling types: overfilled lakebasin, balancedfilled lakebasin and underfilled lakebasin. By summarizing the lithofacies and sequencestratigraphic characteristics of QuantouNenjiang Formations of  Songliao Basin, China in the MidLate Cretaceous period, we compared Songliao Basin to this classification of lakebasin filling types proposed by Bohacs and built up a primary framework of Songliao lakebasin filling types in that period, so that we can go deeper to analyze and summarize the characteristics of their source rock distribution and organic matter burial.

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    Fractal and chaos research of geomagnetic polarity reversal. 
    SHEN Wei FANG Cong-Hui ZHANG De-Hui
    2009, 16(5): 201-206. 
    Abstract ( 1656 )   PDF (813KB) ( 1559 )  

     It is generally acknowledged that geomagnetic polarity has reversed many times in geological history. However, the causes have been unknown up to now. The fractal and chaos theories have been applied to analyzing the phenomenon in geomagnetic polarity reversal. The temporal intervals of geomagnetic polarity reversal have the characters of fractal. The system of earth magnetic field maintains a sort of temporal or spatial order structure by exchanging substance and energy with outside continuously. Random of reversal geomagnetic polarity has the selfreversion characteristic of chaos and chaos theory gives a simple and clear explanation for the dynamic cause of geomagnetic polarity reversal.

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    MISS in Mesoproterozoic nonstromatolitic limestones: A case study from the third member of Gaoyuzhuang Formation at Qiangou section in Beijing.
    MEI Mian-Xiang GAO Jin-Han MENG Qiang-Fen
    2009, 16(5): 207-218. 
    Abstract ( 1715 )   PDF (2480KB) ( 772 )  

     Stromatolitic carbonate succession is common in the Precambrian. In the Yanshan Area, the third member of the Mesoproterozoic Gaoyuzhuang Formation is made up of a particular limestone succession with the sparseness of stromatolites, and this limestone succession has been defined as the nonstromatolitic carbonate succession. For the nonstromatolitic carbonate succession, the third member of the Gaoyuzhuang Formation at the Qiangou section in Beijing is a typical example, in which three thirdorder sequences can be discerned according to the cyclicity reflected by successions of sedimentary facies. Within these thirdorder sequences, there are many subtidal carbonate cycles that are made up of both the mediumto thinbedded aphanitic micrites and the thinbedded marls in the transgressive and the early highstand system tracts, and many grotesque sedimentary structures are developed in the bedding planes of aphanitic micrites. These sedimentary structures, including the domal structure, the irregular reticular and the irregular chaotic tepee ridges, and the palimpsest ripple, make up an association of the microbial induced sedimentary structure (MISS). Therefore, both the special MISSs and the particular lithological types make the third member of the Mesoproterozoic Gaoyuzhuang Formation at the Qiangou section become the representative of the Precambrian nonstromatolitic carbonate succession. More importantly, this succession was formed during the stromatolitic golden age, which provides useful information for the further understanding of the evolving carbonate world of the Precambrian.

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     Progress of research on carbonate diagenesis.
    HUANG Sai-Jing ZHANG Xue-Hua LIU Li-Gong HUAN Jin-Lai HUANG Ge-Ge
    2009, 16(5): 219-231. 
    Abstract ( 2460 )   PDF (2043KB) ( 1183 )  

    Carbonate diagenesis is one of the most active fields in sedimentology. The related research results directly influence peoples understanding about the formation mechanisms of carbonate oil/gas reservoirs and stratabounded deposits. In recent years, carbonate diagenesis has gotten prominent achievements in many fields, including the following aspects. (1) Man has succeeded in precipitating the dolomite with superstructure reflection under the conditions of bacterial sulfate reduction environment of sea water (lagoon) at normal temperature. (2) Hydrothermal dolomitization as the main model becomes the focus of the study. People come to an understanding that hydrothermal dolomite reservoirs, sedimentary exhalative (SEDEX) PbZn deposits and Mississippi valley type (MVT) of PbZn deposits have similar formation mechanisms. They are all controlled by the tectonics (extensional or/and strikeslip (wrench) faults) and fluid flow. (3) More attention is being focused on the deepburial closedsystem dolomitization. Some dolomitization of practical significance to the oil/gas reservoir and to the stratabounded deposits mainly occurred in closed system, which is different from the open system in the contribution to the change of reservoir space and the corresponding geochemical index. (4) Mixingzone model for dolomitization is being questioned. The typical Dorag model in Wisconsin of USA is restudied. Based on the studies using the fluid inclusions method, cathodoluminescence analysis, thin section identification, and stable isotope testing, and combined with organic maturity data, we concluded that the waterrock interaction relating to dolomitization is caused by the concentrated brine relating to increasing temperature. The dolomitization resulted from hydrothermal diagenesis. (5) The meteoric diagenesis mechanism is being challenged. The recent research shows that largescale sea level lowstands may not have chemically active meteoric lenses. The marine environment can produce mature limestone. The sea water can be under saturated with respect to carbonate by the result of bacterial sulfate reduction, which challenges a number of current diagenetic paradigms. (6) Strontium isotope is widely applied to the study of marine carbonate. Different from the oxygen and carbon isotope which has fractionation affected by temperature, pressure and microbial action, strontium isotope of mineral can directly reflect the isotopic composition of fluid. Meanwhile, the marine strontium isotope in geology history has particular long time trends, which make the tracing of marine carbonate strontium isotope composition be widely used in the postsedimentary fluid. (7) Influence of sulfate reduction on carbonate diagenesis has been paid more attention, which include the decrease of kinetic inhibitor for dolomitization or dolomite precipitation, the dissolution and alteration of carbonate reservoirs by H2S and CO2 that are the products of TSR, and the increase of the content of strontium in diagenetic pore water to form celestite deposits.

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    A possible new chromium mineralization: A discussion on the formation of chromespinel of Gangshang ultramafic rocks in Sulu UHP belt.
    CHEN Shi-Zhong YANG Jing-Rui
    2009, 16(5): 232-244. 
    Abstract ( 1639 )   PDF (2192KB) ( 780 )  

     Gangshang ultramafic rocks are mainly composed of garnet peridotites and dunite, which contain olivine, chromespinel, diopside, endiopside, and/or garnet, orthopyroxene, amphibole and phlogopite. Chromespinels in Gangshang ultramafic rocks are varied in composition, with Cr#[100Cr/(Cr+Al)] ranging from 51 to 89, and its variation in composition is related to the four stages of the evolution of ultramafic rocks. Along with the evolution of ultramafic rocks, Cr# of chromespinels was increasing, Mg#[100Mg/(Mg+Fe2+)] of chromespinels was decreasing and the oxygen fugacity was increasing.  In the course of amphibole facies and greenschist facies retrometamorphism, Cr, Mg and Al of chromespinels were reducing, but Fe was relatively increasing. The shearing deformation of the Gangshang ultramafic rocks in the late stage was also helpful to the enrichment of chromium and to the formation of chromespinel.

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    Research on the Quaternary finefraction lithofacies and sedimentation model in Tainan Area, Qaidam Basin.
    XIE Zong-Kui
    2009, 16(5): 245-250. 
    Abstract ( 1884 )   PDF (1192KB) ( 837 )  

    The lacus sediments in Sebei Formation of Quaternary in Tainan Area, Qaidam Basin is developed along one of the growing lowuplifting dome in the center of the depression basin. The sediments are weakly cemented as siltstone and mudstone. Data from core that was cored under sealing highpressure nitrogen environment were adopted in this study. It is proved that 7 types of lithofacies and 5 types of lithofacies group could be classified in the Sebei Formation of Quaternary in Tainan Area. Accordingly, 3 types of microfacies (called energy units sometimes) could be acquired, which are sandbar, matstone and matmud. These 3 types of microfacies distributed orderly. Sandbars concentrated on the higher position of the dome and close to the low water surface of lacustrine. Matstones concentrated on the flank of the dome and under the low water surface of the lacustrine. Sandbars set among matstones often. Matmud concentrated in the trough bend and could extend to the entire area when the lake surface moved upward relatively. The physical property of sandbars is better than that of matstones, and the heterogeneity of matstones are better than that of sandbars. Matmud acted not only as the biogenesisgas generating rock but also as the infiltrating barrier wall of the natural gas.

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    Application of spatial database in quantitative study of lithopalaeogeography—A case study of a Middle Ordovician sequence interval in Ordos Basin.
    LI Bin CHENG Chang-Jing
    2009, 16(5): 251-263. 
    Abstract ( 2283 )   PDF (3345KB) ( 1036 )  

     In the study of sequence lithopalaeogeography, the quantitative analysis, precise calculation and detailed comparison of tremendous geological data, such as field profiles, logging records and seismic curves from different areas, are the basic requirements. In order to obtain a more reliable and precise result, we have developed a method, by using the spatial database to manage effectively the data that cannot be treated by traditional ways. Various attributes of the basic stratigraphic units and their characteristics, such as sequence thickness, penecontemporaneous dolostone content, shallow water plaster content, and terrigenous material content, can be fully utilized statistically in facies analysis and in mapping. Based on this analysis, we have exerted singlefactor isopachous mapping quantitatively for each of the Ordovician sequences in the basin, and we used a single factor formula to delineate the borders of facies units. Finally synthesis multiple factors have to be used to reconstruct the lithopalaeogeography for each of the sequence intervals. The study shows that the proposed method is quite effective and has a much higher resolution in recognizing lithopaleogeographic subunits than traditional ways. For example, in one of the Middle Ordovician sequence interval (444446 Ma) of the Ordos Basin, we have successfully mapped the precise distribution of various facies units, such as old land, submarine uplift, up tidal flat, middle tidal flat and down tidal flat.

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    Another type of oil and gas differential accumulation: Differential dissolution.
    LIU Jing-Jiang LIU Che-Xiang WANG Shen-Liang MAO Guang-Zhou
    2009, 16(5): 264-272. 
    Abstract ( 1423 )   PDF (2656KB) ( 693 )  

     The classical differential accumulation theory describes a process of oil and gas accumulating in a series of correlative traps as that differentially accumulating in a series of traps with better sealed caprocks, or that differentially leaking in a series of traps with bad caprocks. When the new oil or gas recharged into an old reservoir, it should be accumulated by another process of differential accumulation, which is the differential dissolution. The differential dissolution indicates that the new oil and gas would be dissolved as well as entrapped in the preexisting reservoir when they migrate to the traps, i.e., the new oil and gas will accumulate in an old reservoir by a process of dissolution. The hypostasis of differential dissolution is that the molecules of oil and gas dissolve and diffuse differently. The differential dissolution makes oil and gas distributed in the reservoir complicatedly, but with certain regularity: the traps close to the source would be fully filled with dry gas or condensational gas, and those far away from the source would be filled with oil.

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    Analysis on timespace characteristics of coalmine accidents.
    CHEN Bei
    2009, 16(5): 273-279. 
    Abstract ( 1848 )   PDF (2063KB) ( 1697 )  

     Seventy percent of coalmine accidents in China not randomly occurred, but in serials. Most occurred on neighbor coalmine; some were even companied with earthquakes nearby. Certainly, some coalmine accidents occurred independently. It seems that some unknown elements controlled accidents. If these elements are made sure, and measures be taken, it would be of benefit for coalmine safety in production. (1) Coalmine shouldnt fall its rock freely, and there should be conformity among the coalmines. A unified, reasonable stress releasing plan should be made. (2) Neighbor coalmines accidents remind that some accidents may occur in its own mining space because stress in a larger scale is fluctuating. (3) A multicoalmine accidents notifying mechanism may need to be set up. Finally, the paper describes a stress monitoring system in which stress fluctuation is monitored, according to which coalmine can arrange its producing process.

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