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Sediment pore-structure and permeability variation induced by hydrate formation: Evidence from low field nuclear magnetic resonance observation
The macro-scale physical properties of hydrate-bearing sediments is in fact controlled by their micro-scale pore-structures. Understanding the changes in pore-structure characteristics of the sediments during the process of hydrate formation is essential to the analyzing and predicting of the sediment properties. In this paper, the formation processes of Xenon hydrate in different sandy samples are measured with the low-field nuclear magnetic resonance (LFNMR) method. The obtained transverse relaxation time (T2) spectra are interpreted for study of the changes in pore-structure and physical properties of the sediments during the hydrate formation. The results show that Xenon hydrates preferentially form in larger pores and only little amount of hydrates formed in smaller pores; the forming rate of hydrate is higher at the early stage of formation but decrease slowly at the later stage; the hydrate formation process also leads to the changes in pore size and pore-size distribution patterns, for examples, the maximum radius and mean radius of the water-phase pores decrease with increasing hydrate saturation, while the fractal dimension of the effective water-phase pores increases with the increasing hydrate saturation; the water-phase permeability decreases rapidly in the early stage of hydrate formation, but slowly decrease since then; the changes of water-phase permeability during hydrate formation are affected by the pore-structures of the sediment; compared to the SDR model and the Kozeny-Carman model, the fractal model of permeability performs better in showing the influences of pore-structure characteristics on the changes of water-phase permeability during the hydrate formation.
ZHANG Yongchao, LIU Changling, LIU Lele, CHEN Pengfei, ZHANG Zhun, MENG Qingguo
doi: 10.16562/j.cnki.0256-1492.2021031501
Marine Geology & Quaternary Geology. 2021, 41(3): 193-202
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Tropical rainfall variations and human activities of last 1 000 years recorded by lake deposits on the Dongdao Island, Xisha Islands
A series of paleoclimate researches have been made in the South China Sea for the past 1000 years, that provided the insights to the understanding of regional climate change pattern and served as the basis to predict and evaluate the future trends of climate change under the joint actions of the human and the nature. Numerous natural archives and proxies are adopted to reveal the climate changes in different regions of China influenced by monsoon and tropical ocean processes. However, due to the lack of high-resolution climate records, our knowledge about the link between precipitation patterns and monsoon variability remains incomplete, particularly in the tropical region. In order to study the rainfall patterns and the history of anthropogenic activities in tropical zones during the time of AD 1000—1700, we studied such proxies as grain-size distribution and magnetic parameters collected from the sediments of the Cattle Pond on the Dongdao Island of the Xisha Islands. The results show that the precipitation on the Dongdao Island is mainly influenced by ENSO activities and the movements of the Intertropical Convergence Zone. Both of the factors will increase rainfall in the study area, which is opposed to the pattern of the Monsoon system. Human activities on the island were vigorous during the Southern Song Dynasty and the Late Ming Dynasty when the climate is humid and rich in rainfall. There are two periods characterized by sandstorms occurred in northern China during the time of AD 1000—1200 and AD 1450—1600 respectively in the Xisha Islands, reflecting the long-distance migration and precipitation of dust by air.
ZHANG Ling, YANG Xiaoqiang, SHANG Shengtan, ZHANG Tingwei, LI Guanhua, RUAN Jiaoyang
doi: 10.16562/j.cnki.0256-1492.2021031603
Marine Geology & Quaternary Geology. 2021, 41(3): 182-192
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Changes of the upper water column at the 45°N North Atlantic since marine isotope stage 3
The 45°N of North Atlantic is located at the central zone of the ice-rafted detritus (IRD) belt of the North Atlantic, where the marine sediments contain rich environmental and climatic information of high-resolution. The sedimentary records there are used for reconstruction of the pale-oceanic environment since the last glacial in this study. IRD contents, planktonic foraminiferal assemblages and their oxygen and carbon isotopes (δ18O and δ13C) from the core Hu71-377, are used as major tools. Combined with AMS14C dating and oxygen isotope stratigraphy, five Heinrich layers are identified in the MIS3 and MIS2, in which the Heinrich layer 1, 2 and 4 have obvious IRD peaks, high relative abundance of Neogloboquadrina pachyderma and light δ18O values, but no obvious light δ18O are observed in the Heinrich layer 3 and 5. The difference in δ18O between the Heinrich layers 3 and 5 and the Heinrich layers 1, 2 and 4 may suggest the impacts of melt water on the upper water column. Further, the offsets between δ13CN.incompta and δ13CN.pachyderma may also reflect the changes in the mixed layer and thermocline during the Heinrich events. The δ13C offsets were close to zero during Heinrich 1 and Heinrich 2, attributing to the vertical mixing of seawater driven by strong winds. And the δ13C offsets became larger during Heinrich 4 and Heinrich 5, indicating that the seasonal thermocline became shallower, which supports the inference of the penetration of the North Atlantic Current. What’s more, the planktonic foraminiferal assemblages may reflect the properties of the water masses in the upper water column, especially the relative abundance of N. pachyderma and Neogloboquadrina incompta may indicate the sea surface temperature (SST) changes during MIS3.
YE Xiaoxian, Harunur Rashid
doi: 10.16562/j.cnki.0256-1492.2020073102
Marine Geology & Quaternary Geology. 2021, 41(3): 114-123
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Types and migration of shelf-breaks in the central and eastern parts of the Northern South China Sea and their origin
This paper focuses on the types and characteristics of shelf-break migration in the Central and Eastern parts of the Northern South China Sea in the period of Quaternary. Based on the data of high-resolution seismic profiles and geological cores, six 3rd order sequences and their boundaries have been identified. Upon the basis, three types of shelf-breaks are recognized as well. They are the shelf-breaks on depositional continental margin, erosional continental margin and tectonic-controlled continental margin from west to east, formed by the joint action of tectonism, underwater channeling, sedimentary supply and other factors.
HUANG Wenkai, QIU Yan, PENG Xuechao, NIE Xin, ZHUO Haiteng, FU Chaogang
doi: 10.16562/j.cnki.0256-1492.2020060801
Marine Geology & Quaternary Geology. 2021, 41(3): 1-11
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Characteristics of the stratigraphic architectures of the shallow sections in deep sea basin on both sides of Kyushu-Palau ridge
The Philippine Basin has the most complex submarine topography in the world due to the movement of the three plates, the Eurasian the Australian and the Pacific. Taking the Kyushu-Palau ridge as a boundary, the West Philippine Basin shows different structural patterns and topographic features with the Parece Vela Basin where abundant deep-sea geological phenomena and geomorphic features occur.. The high-resolution profiles of the deep seabed can be acquired with the parametric array shallow layer profiler forits transmitting characteristics of difference-frequency and narrowband beam. In this paper, the characteristics of submarine landslides, the sedimentary differences around sea-knolls and the migration of shallow gas and submarine fluid are carefully studied with the East-West trending shallow strata sections across the ridge. The Genetic mechanism of the geological characteristics is discussed by the integration of structural and topographical features. The research of shallow stratigraphic architectures made on vertical short-time scale may provide more evidence and ideas for the sedimentological and geological researches of the region.
YANG Huiliang, WEI Jia, LI Panfeng, LIU Changchun, DONG Lingyu
doi: 10.16562/j.cnki.0256-1492.2020072202
Marine Geology & Quaternary Geology. 2021, 41(1): 14-21
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High-resolution oxygen isotope records of Tridacna gigas from Palau, Western Pacific and its climatic and environmental implications
Tridacna gigas is the largest marine bivalve, and its hard and dense aragonite shells usually have annual and daily growth lines, which have been demonstrated to be an ideal material for high-resolution paleoclimate research. The oxygen isotope has been widely used in Tridacna paleoclimate studies. However, the oxygen isotope of Tridacna shells must be accurately calibrated by modern geochemical process before paleoclimate reconstructions. Palau is located in the northwestern edge of the Western Pacific Warm Pool. Long-lived Tridacna spp. is a common species in the coral reefs of Palau Islands, which may provide abundant materials for paleoclimate reconstructions. In this study, we present a high-resolution oxygen isotope profile from the inner shell of a modern living T. gigas specimen PL-1 from Palau. The high-resolution chronology of the oxygen isotope profile is determined by the clear daily growth layers in the inner shell. The result suggests that the δ18Oc profile of the T. gigas shell has no obvious trend, indicating that the vital effects have no significant influence on the oxygen isotope of shell. Combining with the instrumental data, we found that the ENSO activities in the tropical Pacific had impacts on the regional hydro-climate changes of Palau, and left some fingerprint in the oxygen isotope of Tridacna shell. This study indicates that the daily growth layer and the oxygen isotope in the inner shell of Tridacna from Palau have the potential for high-resolution paleoclimate research.
WEN Hanfeng, ZHAO Nanyu, LIU Chengcheng, ZHOU Pengchao, WANG Guozhen, YAN Hong
doi: 10.16562/j.cnki.0256-1492.2020101101
Marine Geology & Quaternary Geology. 2021, 41(1): 1-13
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Research progress of the Holocene paleoflood in the Yellow River basin and a future prospect
The study of Holocene paleoflood can remedy the limitation of modern flood monitoring records in time and space, and more scientifically identify the flooding regulations and mechanisms. It has gradually become one of the hotspots of the research of global changes. Due to the unique geological conditions in the Yellow River basin, floods have frequently happened in the Holocene history. The present flood risk is still very high in the basin, and therefore, it is one of the key areas of paleoflood research in China. This paper focuses on the research results of the paleoflood in the Yellow River basin published in the past ten years with special interests in sedimentary characteristics, hydrological reconstruction, chronological framework, and its relation to the rise and fall of civilization. Key problems and development trends of the current researches are also discussed, and it is suggested that the records of ancient floods at different geomorphologic locations in the basin should be further collected.
ZHANG Peng, YANG Jinsong, ZHAO Hua, LIU Zhe, SONG Lei, ZHANG Run, CAO Wengeng
doi: 10.16562/j.cnki.0256-1492.2020042601
Marine Geology & Quaternary Geology. 2020, 40(6): 178-188
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Numerical study on the movement of the decomposition front of natural gas hydrate under depressurization
In the process of hydrate decompression, there occurs a decomposition front between the decomposed and undecomposed regions of gas hydrate reservoir. Studying the movement of the decomposition front may help to understand the hydrate decomposition characteristics and further predict the gas volume, which will provide a scientific reference for the actual exploitation potential. In this paper, a one-dimensional and three-phase mathematical model is established. After analyzing the parameter magnitude, the movement of gas and water in hydrate reservoir is regarded as steady flow, and the decomposition front is calculated. Meanwhile, the temperature field equations were dimensionless trans-formed to obtain the transcendental equations for calculating temperature. Combined with the model example, it is considered that the movement of the hydrate decomposition front is linear with the square root of time, and the gas production rate rapidly decreases to a stable value after reaching the peak in the early period. In addition, based on the results of the first trial production in Shen Hu area of the South China Sea, it is found that the total gas production calculated by the model is higher than the actual trial production value, and the relative error is within the acceptable range. Therefore, this paper provides a new simple calculation method for hydrate exploitation characteristics, and gives an optimistic prediction for the exploitation potential. Finally, through sensitivity analyses of the initial temperature, absolute permeability and porosity, it is found that with the increase of the initial temperature and permeability of the formation, the moving distance of the hydrate decomposition front will increase, and the initial formation temperature has a significant effect on the decomposition of hydrate. As the porosity of the formation gets greater, the movement rate of the decomposition front decreases, the moving distance decreases, and the pressure difference between the wellhead and the decomposition front decreases. At this time, the movement of the decomposition front is determined by the thermal physical parameters of the reservoir.
PENG Yingyu, SU Zheng, LIU Lihua, JIN Guangrong, WEI Xueqin
doi: 10.16562/j.cnki.0256-1492.2020072701
Marine Geology & Quaternary Geology. 2020, 40(6): 198-207
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Accumulation model of natural gas hydrate in the Beaufort-Mackenzie Delta Basin, the Arctic
The Beaufort-Mackenzie Delta is an Arctic basin which contains abundant conventional hydrocarbon and natural gas hydrate. It is also one of the earliest regions in the world to carry out producing test of natural gas hydrate. To study the coexistence relationship between the hydrate and conventional hydrocarbon in the basin has not only direct significance to energy resource exploration, but also important theoretical and practical significance to seabed stability assessment, global climate change and carbon cycle research. In this paper, geological factors and stability conditions for hydrate reservoir generation was systematically summarized based on the large number of data available. Furthermore, combined with the analysis of glacier evolution, it was concluded that the accumulation of natural gas hydrate in the basin is controlled by the leakage of the underlying petroleum system and the change in permafrost zone. It is revealed that the gas source of hydrate in the basin is mainly the thermogenic hydrocarbon gas coming from the buried petroleum system. The activities of tectonic elements, such as faults and folders, were positively correlated with the enrichment of hydrate, and the hydrate occurrence was mainly related to the sand bodies of the delta plain in the Iperk, Kugmallit and Richards sequences. The permafrost above the hydrate stabilization zone plays a key role in the accumulation of gas hydrate.
YANG Chupeng, LIU Jie, YANG Rui, YAO Yongjian, LI Xuejie, SU Ming
doi: 10.16562/j.cnki.0256-1492.2020052602
Marine Geology & Quaternary Geology. 2020, 40(6): 146-158
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Methane migration and consumption in submarine mud volcanism and their impacts on marine carbon input
Submarine mud volcanoes contribute carbon to the hydrosphere and the atmosphere by releasing methane-rich fluids, and researches on the temporal and spatial distribution of methane migration and chemical transportation at submarine mud volcanoes are the keys to understanding the processes mentioned above. In this paper, a large number of domestic and foreign literatures are systematically investigated, and the strong heterogeneity of methane leakage was recognized in the mud volcano systems. Methane emissions mainly occur during the eruption and dormant periods of mud volcanoes, and only a small amount of leakage occurs in extinct periods. In space, strong methane bubble leakages are usually developed around the centers of mud volcanos, and the chemical transportation efficiencies of methane are low in sediments; the leakages of methane and DIC controlled by fluid flow are mainly developed in the wings, where the rates of anaerobic oxidation of methane and the precipitation rate of authigenic carbonate are the highest. Shallow sediments have the strongest interception to carbon emission; both the intensity and the transportation rate of methane in the edge area are low, and hence a large area of DIC microleakage is developed. Globally, the carbon flux from submarine mud volcanos into shallow sediments is ca. 0.02 Pg C·a−1. The methane and DIC coming from sediments could cause seawater anoxia, acidification, and change air-sea carbon exchange fluxes, which may affect the ocean’s ability to absorb atmospheric carbon dioxide on millennium scale or even in a shorter time, and thus impacts on the global climate environment. In the future, accurate statistics on the number and eruption cycle of submarine mud volcanoes, and detailed investigations on the migration and transportation of methane in typical submarine mud volcanoes with different sizes and development stages, will be helpful to further accurately estimate their total carbon emissions, to study the impacts of bottom-up mud volcanoes’ carbon emissions on the marine carbon cycle, and to improve the marine carbon cycle model.
XU Cuiling, SUN Zhilei, WU Nengyou, ZHAO Guangtao, GENG Wei, CAO Hong, ZHANG Xianrong, ZHANG Xilin, ZHAI Bin, LI Xin
doi: 10.16562/j.cnki.0256-1492.2020050801
Marine Geology & Quaternary Geology. 2020, 40(6): 1-13
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Development of engineering-geological parameters evaluation system for hydrate-bearing sediment and its functional verification
Engineering-geological parameters are crucial for evaluation of geohazard potential in marine hydrate exploitation. The combination of piezocone penetration and vane shear test may help gain longitudinally continuous and reliable parameters for hydrate reservoir, which has great perspective in integrated engineering and geological field survey. However, application of these techniques to marine hydrate survey has remained vacant so far. To better understand the penetration or shearing behaviors and their influencing factors in hydrate-bearing sediment (HBS), we developed a novel engineering-geological parameters evaluation system, which may satisfy the need of five-bridge piezocone penetration test and vane shear test. The tip resistance, side frictional resistance, excess pore pressure, electrical resistance, and video along the penetration path could be obtained through five-bridge piezocone penetration test. The method of electrical resistivity tomography is firstly combined with piezocone penetration and vane shear technology in this system to explain the relationships between engineering geological parameters and hydrate saturation. The sandy sediment and clayey-silt sediment (free of hydrate) are involved to verify the functions of the system. The results show favorable fitness with the field-obtained data. Repeated experiments show high reproducibility of the data. This system proved the possibility of establishing quantitative evaluation models of engineering geological parameters in HBS, and also provided a basic platform for novel probing device test in the integrative engineering-and-geological hydrate survey.
LI Yanlong, CHEN Qiang, LIU Changling, WU Nengyou, SUN Jianye, SHEN Zhicong, ZHANG Minsheng, HU Gaowei
doi: 10.16562/j.cnki.0256-1492.2019110401
Marine Geology & Quaternary Geology. 2020, 40(5): 192-200
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Characteristics, distribution and implication of hydrothermal minerals in Tianxiu Hydrothermal Field, Carlsberg Ridge, northwest Indian Ocean
Hydrothermal minerals could originate from mass wasting of hydrothermal deposits or from the hydrothermal plume falling-out. The types and their spatial distribution of hydrothermal minerals are important indicators for constraining the location of hydrothermal field. The Tianxiu Hydrothermal Field (3°41′N,63°50′E) is an ultramafic-hosted field located on the Carlsberg Ridge, northwest Indian Ocean. In this paper, surface sediments collected from 4 stations near the active venting site of Tianxiu Hydrothermal Field and its surrounding regions were studied on hydrothermal minerals to understand their spatial variations on morphology, composition, abundance and particle size. Near the venting site (0 ~ 0.22 km) the hydrothermal minerals are dominated by Cu-Zn-Fe containing sulfide aggregates, in the size from gravel to sand, originated from the mass wasting of the sulfide deposits and precipitation from the hydrothermal fluid. For samples collected outside of the hydrothermal field (1.84 ~ 6.05 km away), the hydrothermal minerals are dominated by fine grain hydrothermal oxides and hydroxides derived from plume fallout. Our results suggest that the types and grain size of hydrothermal minerals and their spatial distribution can be served as a good indicator for tracking unknown active and inactive hydrothermal field and prospecting of the associated hydrothermal sulfide resources.
CAI Yiyang, HAN Xiqiu, QIU Zhongyan, WANG Yejian, LI Mou, Samuel Olatunde Popoola
doi: 10.16562/j.cnki.0256-1492.2019101201
Marine Geology & Quaternary Geology. 2020, 40(5): 36-45
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Research progress in seamount influence on depositional processes and evolution of deep-water bottom currents
Seamount is a kind of tectonic geomorphological features widely distributed in the deep sea around the world, where bottom currents persistently exist, thus the interactions between seamounts and bottom currents are very common and will bring about non-negligible influence on deep-water sedimentation and their evolution. This study summarized the global researches on the deep water sedimentation by bottom currents around seamounts, suggesting that deep-water bottom-current hydrodynamics would change under the direct or indirect influence of seamounts, including the changing in flow paths, generation of secondary bottom currents, and variation in ecosystems. Consequently, deep-water sedimentary morphologies and lithofacies would display special distribution patterns. With the evolution of bottom-current hydrodynamics and sedimentary morphologies, deep water sedimentation processes and associated responses would change as well. In summary, bottom currents are complex and special around seamounts, resulting in sedimentary morphologies and lithofacies features as well as distribution patterns differing from those on the open slope. Thus, the sedimentary morphologies and lithofacies formed under bottom currents around seamounts have very particular implications for basin structures and palaeoceanography evolution. However, there is still lack of study concerning the coupling relationship between seamounts and deep water sedimentation processes, greatly limiting deep-sea resource exploration and geo-hazard study, thus more attention is required to be paid to the relationships in the future research of deep-water sedimentology.
WANG Xingxing, CAI Feng, WU Nengyou, LI Qing, SUN Zhilei, WU Linqiang
doi: 10.16562/j.cnki.0256-1492.2019111101
Marine Geology & Quaternary Geology. 2020, 40(5): 68-78
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Stratigraphic features and controlling factors in the eastern Sub-basin of the Central Basin, South China Sea during the post-spreading period
Driven by sea-floor spreading, the tectonic evolution of a marginal basin could be divided into three stages, namely the pre-spreading, spreading and post-spreading stages. Most of the thick deposits developed in the Central basin of the South China Sea, especially the thickest in the eastern Sub-basin was deposited in the post-spreading stage. Various factors were active in different parts of the eastern Sub-basin, resulting in a great variety of post-spreading stratigraphic features. A great amount of information about the formation and evolution of the South China Sea was preserved in the thick sediments. Therefore, it is important to study the stratigraphic features in the eastern Sub-basin formed during the post-spreading stage. According to the age data from some ODP and IODP drilling holes, the synthetic seismic records passing through the wells were calibrated and then the sequence stratigraphy of the region was established and dated. Upon the basis, we discussed in this paper the characteristics of the strata and related factors. The result shows that deposition of the sediments with stable thickness was mainly caused by stable basement subsidence with substantial terrigenous sediments input from the north, and the micro-plate subducting toward Manila trench was the main influence factor which gave rise to the characters of the strata in different age in the east. The sediments containing certain amount of volcanic debris was deposited in the west and middle part owing to the frequent magmatic activities. And in the south of the basin, turbidite sediment waves occurred due to the control of slope environment.
QIU Yan, DU Wenbo, HUANG Wenkai, WANG Yingmin, NIE Xin
doi: 10.16562/j.cnki.0256-1492.2020053001
Marine Geology & Quaternary Geology. 2020, 40(5): 1-14
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Collision of North China and Yangtze Plates: Evidence from the South Yellow Sea
As an important geological event in East China, the collision of the Yangtze plate and North China plate gave rise to the formation of the Sulu-Dabie orogen. This paper made a thorough review on the different collision models. Data from seismic profiles and seismic tomography support the detachment model to the Lower Yangtze region. It says that the upper crust of the Yangtze Block detached from the lower crust, just like a crocodile opened its mouth, and the North China plate fortunately wedged into it. In the Qianliyan belt there developed similar gravity and magnetic anomalies with Sulu orogen, as the extension of the Dabie-Sulu orogen. In seismic profiles, the South Yellow Sea Basin and Qianliyan Uplift Belt are different in reflection characteristics. There are complete stratigraphic reflections in the basin but no obvious reflections in the uplift. All the boundaries show a south-dipping reflection patterns, suggesting the obduction of the Yangtze Block. The collision and derived compression mainly happened in Triassic while the growth strata deformation formed in lower Jurassic. In the lower crust of the Qianliyan Uplift, the Moho reflection is recognized at ~10 s, and disappeared below the South Yellow Sea Basin. It is thus speculated that the lower crust under the Qianliyan Uplift belong to the North China Plate, and the collision between Yangtze and North China caused the fading out of the Moho reflection. Generally, the geophysical data from the South Yellow Sea support the hypothesis that the North China Block wedged into the crocodile mouth of the Yangtze Block.
CHEN Jianwen, XU Ming, LEI Baohua, SHI Jian, LIU Jun
doi: 10.16562/j.cnki.0256-1492.2019070902
Marine Geology & Quaternary Geology. 2020, 40(3): 1-12
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