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  • 1995 Volume 50 Issue 5
    Published: 15 September 1995
      
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  • ON THE LOWEST SEA LEVEL DURING THE CULMINATION OF THE LATEST GLACIAL PERIOD IN SOUTH CHINA
    Huang Zhenguo, Zhang Weigiang, Chai Fuxiang, Xu Qihao
    1995, 50(5): 385-393. https://doi.org/10.11821/xb199505001
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    There are some different opinions about the lowest sea level during the culmination of the latest glacial period in South China. By using the comprehensive analysis of shelf relict sands, submerged beach rocks. relict landforms. sedimentary cores of sea floor, coral reef and the response in continental area, we suggest that the lowest sea level at that time may be at about -80m.The present elevation of littoral sediment samples is not possible to be used directly to recognize the height of ancient sea level. For exsample, it is reported that some relict sand samples at an elevation of -103--125m dated at 15 844-14 320aBP have been found on the shelf outside the estuary of Zhujiang River. However, dispeling the sinking depth of shelf caused by hydroisostasy and sedimentary load due to the transgrssion during the postglacial period, the original elevation of the samples is actually at -72--87m which can be regarded as the approximate height of the ancient sea level. Similarly the submerged old streams and dunes located at -80--100m may represnt the sea level of -50--70m.The elevations of the indicators of the lowest sea level are varied. for exsample, the beach rocks are at -2--3m and -42m in Shenhuwan Bay and off Nanao Island respectively, the relict sands are at -33--41m in Taiwan Strait and the littoral sediments are even at 2-4m in Putian,Shaoan and Dongshan. It is the result of differential uplift of fault block.Unconformity of Q33 with an elevation of -93--129m can be found in some sedimentary cores from the shelf outside the estuary of Zhujiang River. but the revised elevation is -60- -89m. In some borehole sections of coral reef in South China Sea, unconformity of Q33 between the lower coral reef limestones and the upper gravels with shell fragments can also be seen. its elevation is now -15--17m. because the coral reef islands have been uplifting. However the higher unconformity gives us a idea that the sea level was not so low during the culmination of the latest glacial period. Besides, along the coastal region. some phenomena related to erosion basis such as the -20--60m, Q33 terrestrial sediments bottom layer. the -42--67 mriver beds and the -40--80m bottom of some karst caves also support the conclusion that the lowest sea level was at about -80m.
  • A MACRO EFFECT OF TRANSPORT IN THE CHANGE OF ECONOMIC SPATIAL STRUCTURE
    Rong Chaohe
    1995, 50(5): 394-401. https://doi.org/10.11821/xb199505002
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    Transport is an important impacting factor on economic location all along, but its effect in the changes of economic spatial structure has several stages, going through a course from strong to weak gradually in the developed countries. The paper analyses this kind of change from the angles of time, space and indusrial structure.From the view of time, the theory of transportization, which summarizes the relationship between transport and economic development, provides a new observing angle.Transportization is one of the most important features of industrialization and an economic process accompanying industrialization as well. To some degree, the improvement of structure of economic geography system is reflected in the process of a territorial transportization.Viewed from economic space, industrialization proceeds in an orderly way along the pattern of point-axle-aggregate belt: the big industry first converges in an individual city and then expands along the transport trunk lines and the axial line of other important infrastructures, and after that,radiates and proliferates towards the peripheral regions. After a considerable period of development and construction, there would come to shape important belt-like aggregate areas.In the view of industrial structure, modern transport is an important part of the conditions in which the structure is changed from lower level to higher level. But compared with the lower level industrial structure. the higher level structure depends on more infrastructures, including not only transport, but also tele-communication, modern logistics, computer network, etc. In this stage, industrial locations are less restricted by transport than before, and need more flexibility. The transport’s position in industrial location has descended.According to the paper, China is still in the primary transportization stage, the backward transport system is still restricting economic growth, so the basic relations between transport and national or regional development remain to be the most important issue. In the author’s opinion. at China’s present level of economic development, transport is playing a fairly dominant role in the structural change of its spatial economy. and the progress of transportization must be speeded up in this country.
  • EFFECTS OF GLOBAL WARMING ON PLANT PHENOLOGICAL EVERTS IN CHINA
    Zhang Fuchun
    1995, 50(5): 402-410. https://doi.org/10.11821/xb199505003
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    In this paper, effects of global warming on phenological events of China are discussed.First, it is demonstrated that atmospheric temperature is the most important factor influencing plant phenophase: 1. the integral regresseion method is used to analyse the relationship between meteorological factors and phenophase of trees in spring in Beijing. The calculated results show that the relation between meteorological factors and phenophase is close. But the most important factor which influence the phenophase of trees in spring is temperature and their correlation coefficient is more than 0. 7. The sunshine and precipitation are not important factors. If precipitation and sunshine are similar to those in normal years. they may be analysed in three intervals:pre-winter、winter and spring. The effect of spring temperature on phenophase is the most important. At that time. the higher the temperature is. the earlier the phenophase occurs. The temperature effect in pre-winter period is similar to that in spring, but the intensity of the effects is smaller. The low temperature in winter also affects the phenophase in spring. but the higher the temperature in that time. the later the phenophase. It is shown that low temperature in winter is also an essential condition for the phenophases occurs. Secondary. the correlation coefficient between phenophase and annual mean temperature is calculated and the value is higher.Because atmospheric temperature is the most important factor on phenophase. a linear model contains only phenophase and annual mean temperature factors are established by the author. Finally, we apply this model to evaluate changes of the phenological events in China for future global warming scenario. The calculated results are as follows:1. Assuming a 2℃ rise of annual mean temperature. trees phenological events of spring in China will occur about 3-4 days earlier, but may be postponed for 3-4 days in autumn. The greenleaf stage will be prolonged for 6-8 days.2. Assuming the scenario of a doubled CO2 content on the next century which caddses a 1. 0- 1. 8℃ rise in the annual mean temperature in China, phenological events in China will be 4-6 days earlier in spring, but will be postponed 4-6 day in autumn. The green-leaf stage is prolonged for 10-12 days. The mature date of fruits and seeds may be earlier. Moreover. the number of days in the changes of phenological events in the nothern part of China will be more than those in the southern part.
  • ANALYSIS OF TRANSPORT MECHANISM OF WATER AND SUSPENDED SEDIMENT IN THE TURBIDITY MAXIMUM OF THE CHANGJIANG ESTUARY
    Shen Jian, Shen Huanting, Pan Dingan, Xiao Chenyou
    1995, 50(5): 411-420. https://doi.org/10.11821/xb199505004
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    According to the field data of continuous measurements of current velocity, current direction,concentration of suspended sediments and salinity during two tidal cycles at eighteen stations in the North Channel, the North Passage and the South Passage of the Changjiang Estuary in the spring tide in August, 1978. by making an analysis of water and suspended sediment flux of a width unit across the main channel of each tributary, the action of each term of suspended sediment transport in the turbidity maximum of the Changjiang Estuary is discussed and the relative importance of each term in three different tributaries is compared in this paper by introducing techniques of mechanism decomposition. The result indicates that: (1) The dominant mechanism of net transport of water and suspended sediment is that of non-tidal steady advection transport, mass Stokes drift. tidal trapping and net vertical circulation. (2) The net transport of water and suspended sediment induced by mass Stokes drift is of considerable importance in each tributary of the Changjiang Estuary and has a feature of landward movement. which restrains the seaward transport of suspended sediments and induces the increase of suspended sediment concentration within the estuary. (3) The magnitude of suspended sediment transport induced by tidal trapping is greater than that induced by vertical shearing diffusion. Tidal trapping with the resuspension of bedload play an important role in the formation of turbidity maximum in the area where the action of tidal trapping is distinct. The resuspension of bedload and the asymmetric sediment transport are the main factors that induce the distinct action of tidal trapping. (4) In different tributaries, the contribution of each suspended sediment transport term to net sediment transport varies with the relative importance of runoff and tidal current. Mass Stokes drift and tidal trapping play important roles in the formation of turbidity maximum in the South Passage where tidal current is stronger. In the North Channel where runoff is relatively strong. the non-tidal steady advection transport and net vertical circulation occupy dominant positions and the later is the main factor fn the formation of turbidity maximum. In the North passage,it is between the South Passage and the North Channel.
  • A STUDY ON THE SEDIMENT DYNAMICS OF EBB-TIDAL DELTA OF ZHANJIANG HARBOR TIDAL INLET
    Zhang Qiaomin, Zheng Deyan, Li Shaoning,Chen Xinshu, Yu Hongping, Li Wei
    1995, 50(5): 421-429. https://doi.org/10.11821/xb199505005
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    Zhanjiang Harbor is the largest tidal inlet along South China coasts and the largest ebb-tidal delta developed in the inlet entrance area. This paper analyzed the basic characteristics of the ebb-tidal delta of Zhanjiang Harbor including the morphological structure (semi-circular shoals around central trough), surface sediment distribution (coarse sand to very fine sand with little silt and clay from center to periphery) and hydrodynamical field structure (ebb tidal current dominant in the main ebb-tidal channel, and wave and flood tidal current domimant in the semi-circular shoals). and discussed the sediment dynamics of the hydrodynamical of ebb-tidal delta, the close interrelation among morphology, sedimentology and hydrodynamics, and the sediment transport pattern of the ebb-tidal delta of Zhanjiang Harbor.
  • A STUDY OF THE TRANSIENT AND TIME-DEPENDENT GREENHOUSE GAS-INDUCED CLIMATE CHANGE
    Zhao Fengsheng, Shi Guangyu
    1995, 50(5): 430-438. https://doi.org/10.11821/xb199505006
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    Greenhouse gas-induced global climate change has been attracted much attention in recent years. Model studies suggest that the equilibrium warming for a CO2 doubling is 1. 5 ℃-4.5℃ (climate sensitivity). However. because the huge thermal capacity of the ocean will delay and effectively reduce the climate response to the increase in the concentration of the greenhouse gases, at a given time, the realized global surface temperature will only reflect part of the equilibrium change for the corresponding instantaneous value of the radiative forcings induced by greenhouse-gases. In this study, we have developed a coupled EBM/BD model to study the greenhouse-gas induced transient and time-dependent change of global mean temperature. The model consists of three parts, i. e., the atmosphere, land and ocean. The atmosphere and the land are considered as boxes. The ocean is divided into a oceanic mixed layer, a thermocline layer and a bottom layer. The heat exchanges of atmosphere-land,atmosphere-oceanic mixed layer and land-oceanic mixed layer are described by using the energy balance model developed by Wigley and Schlesinger. The heat exchanges of oceanic mixed layer-thermocline layer, mixed layer-bottom layer and thermocline layer-bottom layer are described by using our BD model previously developed for study of the carbon circle. The validity of the model is investigated by comparing the simulated and observed vertical distributions of ocean water temperature. A doubling CO2 experiment is performed to investigate the response of the ocean surface temperature to the increase in the concentration of the greenhouse gases. In the experiment,the radiative forcing due to doubling CO2 is 4. 23w/m2. The results show that the thermal inertia of the ocean provides a time lag of about 1 1. 08- 101. 48 years, depending on the values of climate sensitivity. The model is also used to simulate the variation of the ground surface temperature in the past 100 years by using the radiative forcings derived from the concentrations of greenhouse gases given by Wigley. The results show that the ground surface temperature has risen about 0. 35-0. 64℃. corresponding to the climate sensitivity of 1. 54-4.5℃. Such results are consistent with the observed rise of about 0. 3℃-0. 6℃. The consistence between the simulated and observed rise of the ground surface temperature indicates that the increase in the concentrations of the greenhouse gases plays a main role in the rise of the ground surface temperature in the past 100 years. The CO2 concentration of the next century has been simulated by using the BD model for several emission scenarios given by IPCC. If the humankind does not control the CO2 emissions from now. the CO2 concentration will reach a value of 743ppmv at the end of the next century. If the CO2 emissions are reduced at a rate of 2% per year. the CO2 concentration will slowly increase until 2050 and reach a peak value of 390ppmv. After 2050, the CO2 concentration will decrease. If the CO2 emissions are stopped from now, the CO2 concentration will slowly decrease and reach a value of 320ppmv at the end of the next century. The variations of the ground surface temperature of the next century are estimated by using the coupled model. The results show that. if the humankind does not control the CO2 emissions, the ground surface temperature at the end of the next century will rise about 1. 64℃-3. 08℃ for the climate sensitivity of 1. 5℃-4. 5℃. If the CO2 emissions are reduced at a rate of 2% per year, the ground surface temperature will slowly rise in the beginning and middle decades of the next century. The ground surface temperature will not change in the late decades. If the CO2 emissions can be stopped from now, The ground surface temperature will decrease slowly.
  • EXPLORATION ON LAWS OF SPATIAL VARIATIONS OF INDUSTRIAL LAND IN REVENUES WITHIN URBAN AREA: A CASE STUDY OF TIANJIN
    Wang Baoming
    1995, 50(5): 439-446. https://doi.org/10.11821/xb199505007
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    This paper discusses spatial variations of industrial land in revenues in Tianjin. The closer the industrial land to the central zone, the more the revenues can be obtained. The key factors that affect the spatial variations in revenues, such as differential rent Ⅰ, differential rent Ⅱ. additional capital investments or labor inputs. are pointed out. Then the paper employs mathematical models to analyze how these factors contribute to the spatial variations separately. The results show that the contribution of differential rent Ⅰ to the spatial variations in revenues is 46. 5%. that of differential rent Ⅱ is 17. 4%. that of additional capital investment is 25. 02%, that of additional labor input is 10.34%, and that of other factors is only 0. 98%. Finally, it is proved that the spatial variations of industrial land in revenues are mainly resulted from the difference in location.
  • A STUDY ON THE HOLOCENE BURIED TIDAL SAND BODIES IN THE SOUTH YELLOW SEA COASTAL LAND
    Chen Baozhang, Li Congxian, Ye Zhizheng
    1995, 50(5): 447-458. https://doi.org/10.11821/xb199505008
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    Based mainly upon anlysing of eight drill-holes and upon other several dozens ofis paper. It is non-marine facies of Pleistocene that under lay the sediments of Holocene with an unconformity between them. The Holocene sedimentary sequences can be divided into the lower transgressive and the upper regressive ones, consisting of beach facies (contains estuary-bay facies in some part of the studied area), nearshore neritic facies (tidal sand body facies) and tidal flat facies. It is obvious that facies change horizontally. It merits notice that the nearshore neritic facies is composed of fine sands or silty fine sands in all drill-holes. Characteristics of the sand bands have been researched about their textures, structures, minerals and microfossils etc. Through comparative sedimentological study with the modern tidal sand ridges in Jianggang, it is found that the buried sand bodies belong to the type of tidal sand body.Tidal sand body refers to the sand body of geomorphological bedform formed by the tide current.Along with the changes in current power and sand source, the bedform appears diffenent shapes, and forms different types of tidal sand bodies.According to the differences in their sedimentological characteristics and microfossils, the buried tidal sand bodies can be distiguished into three types: Ⅰ) nearshore tidal sand bars, Ⅱ ) tidal sand waves. and Ⅲ ) nearshore tidal sand ridges. They correspond respectively to the sand banks discribed by Stride (1982) and Caston (1972), the sand waves discribed by Stride (1982) and Belderson (1966) and the sand ribbons discribed by Stride (1982),Kenyon (1970) and Off (1963) or sand ridge discribed by Swift ( 1975 ).
  • A SEA-RUNNING CHANGJIANG RIVER DURING THE LAST GLACIATION?
    Li Congxian, Zhang Guijia
    1995, 50(5): 459-463. https://doi.org/10.11821/xb199505009
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    Numerous boreholes demonstrate that there is indeed an incised paleo-valley stretching into the East China Sea from Zhenjiang and Yangzhou at the apical area of the Changjiang Delta. The filling deposits in the paleo-valley are of fluvial. neritic and deltaic facies. The fluvial sedimentary unit composed of sand with gravels and sand at the low part, and of grey sandy clay with sandy lenses at the upper part, is a fining-upward sequence with erosional boundary at its bottom. The unit was formed by retrogressive aggradation in process of the postglacial transgression. The 14C datings show that the fluvial unit was deposited during the postglacial period while the sea level rised rapidly and the paleo-valley was incised when the sea level lowly standed. The fluvial facies is overlain by the neritic facies which consists of grey mud rich in marine microfossils-.The deltaic facies including mouth bar sand and distributary sandy clay covers the neritic facies nearly in the limits of the paleo-valley. The presence of enormous paleo-valleys support that the Changjiang River was still sea-running during the period of sea lowstand in the last giaciation.
  • LOESS MOUNDS ON THE LAIZHON BAY PTAIN SOUTH OF BOHAI SEA AND THEIR PALEOGEOGRAPHIC IMPLICATION
    Zhang Zulu
    1995, 50(5): 464-470. https://doi.org/10.11821/xb199505010
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    The loess mounds are a newly discovered type of landforms on the Laizhou Bay Plain south of the Bohai Sea. Research shows that they were formed in the late period of the Late Pleistocene when the Bohai Sea was esxposed in the period of the late warm ice age and the plain was formed. because the exposed area is not protected by vegetation, the sediments at the sea bottom are blown and transported southward by strong northern winds, and are deposited on the coastal plain. As thick loess layers were formed, the loess mound landforms were formed.
  • ON THE RELATIONSHIP BETWEEN GLOBAL THERMAL VARIATIONS AND THE WET/DRY ALTERATIONS IN THE ASIAN AND AFRICAN MONSOON AREAS
    Yan Zhong Wei, Petit-Maire Nicole
    1995, 50(5): 471-479. https://doi.org/10.11821/xb199505011
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    Based on the various data analyses, the paper aims to making a discussion of the impacts of the past global warm/cold variations on the humidity changesalong the low-latitudinal summer monsoon ranges in Asia and Africa. The ways the regional climates respond to global changes may be quite different at different time-scales.In fact, it is widely noted that at the time-scale longer than 102yr, the summer monsoons are generally stronger during global warmer periods, thus leading to wetter conditions in the presently semiarid and arid regions in Asia and Africa. Dry conditions prevail the most of the areas concerned during cold periods, accompanied by rapid accumulation of loess in north China, lower lake-levels in Qinhai-Tibetan Plateau. desert development in northwestern India, Arabian Peninsula and Sahara.Because the thermal sensibility is generally larger in continent than in ocean. the globally warmer (colder) condition at long time-scale almost always implies a larger (smaller) thermal contrast between continent and ocean in summer, which is nothing but an essential force of monoson. The hightropospheric Easterly Jet and the relevant atmospheric circulations were also proposed as important factors to explain the in-phase humidity variations along Asian and African monsoon ranges.The mentioned global-regional relationship become weaker with decreasing time-scales. At 101-102-year-scales. which receive serious attention at the present in the field of global change study.temperature fluctuations are relatively small but may be locally considerable. Therefore. the themally driven circulations such as monsoons in different areas may not identically change. In recent history some wet/dry alterations at century-scale along the monsoon zones were found to be accompanied with the mild /cold variations of the Little Ice Age, but few evidences indicated the same at decadescale.During the mordern observation period. it was found that the 1920’s global warming was clearly accompanied with the enhanced monsoon rainfall along the Asian and African semi-arid regions and that the 1960s’ cooling led the event drying tend-ency along the same zones. However. the case of the 1980s’/global warming prevent us from clearly defining the global-regional relationship at the medium-term climate scale. We need to not only carefully analyze the long historical evolutions, but also pay much attention to the large-scale geographical patterns of climate changes and their atmospheric circulation backgrounds. The latter remains nowadays a particularly weak link in studying the regional climate changes and their relationship with global change.