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Elemental distribution pattern and forming mechanism of the two types of phosphates in ferromanganese crust in Western Pacific Ocean and their implications
Most of the Pacific ferromanganese crusts have experienced phosphatization before Miocene, presumably by impregnation of phosphorus-rich component into the old crust section during the period of high productivity, that is called the product of phosphatization events. Most of the previous studies on phosphatization were based on point/line analysis of element contents or isotopes, while few studies have been devoted to the growth structure and 2-dimentional element distribution. In this study, a hydrogenetic ferromanganese crust (MDD53) sampled from the western Pacific Ocean was analyzed by electron probe X-ray microanalysis (EPMA) and micro–X-ray fluorescence scanning (μXRF), generating high resolution quantitative data on element concentrations and 2-dimensional element maps, respectively. The results of EPMA and μXRF reveal that the middle to lower part of the crust was phosphatized. The μXRF map shows that there are two types of phosphates. The first type shows sporadic enrichment of Ca and P in the top part of the crust, accompanied by strong post-depositional alterations, such as broken structure, Fe loss, and relatively Mn enrichment. The EPMA data further shows that trace element enrichment of Co and Ni as well as depletion of Pb in the phosphatized area. This observation reflects different affinity of these elements with Fe and Mn oxides, which is consistent with the hypothetic phosphatization mechanism of organic matter degradation at the crust-seawater interface and the resulting alteration of the preformed crust. The second type of phosphate is characterized by an unreported structure of continuous Ca and P enriched laminae located at the bottom of the crust. The lack of post-depositional alteration of the growth structure suggests that this type of phosphate is of syn-depositional or early diagenetic in origin, which is distinctly different from post-diagenetic alteration. The syn-depositional phosphate may indicate an early stage coprecipitation of phosphate and ferromanganese oxide colloids in a relatively shallow water depth, making it a reliable paleoceanographic indicator for high temporal resolution studies of the Late Cretaceous-Early Cenozoic period.
LIU Jiahui, QU Yang, LI Weiqiang, WEI Guangyi, SUN Qianyuan, LING Hongfei, CHEN Tianyu
doi: 10.16562/j.cnki.0256-1492.2021052701
Marine Geology & Quaternary Geology. 2022, 42(2): 36-45
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Temporal-spatial variation characteristics and the controlling factors of temperature and salinity structure in Zhongsha Islands sea area of the South China Sea
The statistical analysis results of CTD measured data of water mass in summer and autumn from the sea area of the Zhongsha Islands show that the sea surface temperature of seawater in the study area is between 30.0 and 31.2 °C, and the highest temperature distributed in the platform of the Zhongsha Islands. The sea surface salinity is from 33.6 to 34.1 PSU, and the highest salinity distributed near the Dong Island. The bottom temperature is from 1 to 25 °C, and salinity from 34.1 to 35.2 PSU, the highest salinity distributed in the southeast corner of the study area. In general, the temperature-salinity structure of the study area is characterized by high temperature, low salt in the surface layer and low temperature, high salt in the bottom layer, and the depth of mixed layer is between 20 and 90 m. The vertical velocity of surface, middle and bottom water in the study area is different, and the velocity is between 0.01 and 0.22 m/s. The seasonal variation characteristics of temperature and salinity in the study area were analyzed according to the FVCOM model. In winter, the sea surface temperature in the south of the study area was significantly higher than that in the north, and the temperature difference between the north and south was obvious. In summer, the distribution of sea surface temperature and salinity is obviously affected by typhoon, and the spatial distribution of sea surface temperature tends to be uniform. The numerical simulation results show that the intensity of flow field in the study area is strength in winter and summer, and weak in spring and autumn. The simulation results also show that extreme weather has a significant effect on the temperature and salinity structure in the study area in a short term, which is manifested as the decrease of sea surface temperature, the increase of mixed layer depth, and the enhancement of vertical mixing effect of water body.
HUANG Cheng, WU Nengyou, WU Xiao, LIU Shiqiao, ZHANG Jingwei, XU Cheng, LIU Liang, DONG Xinzhu, CHEN Liang
doi: 10.16562/j.cnki.0256-1492.2021111301
Marine Geology & Quaternary Geology. 2022, 42(2): 1-14
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Structural characteristics and hydrocarbon exploration prospect of the Laoshan uplift in the South Yellow Sea Basin
Meso-Paleozoic marine deposits widely occur on the Laoshan uplift of the South Yellow Sea Basin. As a new field and layer for oil and gas exploration, it shall be the future targets for strategic discovery of oil and gas and the breakthrough point of exploration understandings. Based on the detailed seismic interpretation results and exploration progress made in recent years, the uplift is divided into two parts, the Qingfeng deformation zone in the north and the Gaoshi stable zone in the south. The Qingfeng deformation zone is a cover-detachment overthrust nappe system characterized by NE trending thrust faults, while the Gaoshi stability zone a weak deformation and stable zone. NW trending synclinal faults are developed in small scale. The fault system of the Laoshan uplift can be subdivided into three groups, NE, NW and nearly EW in trending, and the boundary fault is a reverse fault nearly in EW direction. The deformation of marine structural layer is strong in the north and west and weak in the south and the east, strong in the upper and weak in the lower. The Laoshan fault-uplift area was formed by Indosinian-Early Yanshanian compressional thrust and late Yanshanian-Early Himalayan weak tension/tension torsion, and four structural styles of compressional, tensional, strike-slip and inversional are recognized. Through the analysis of their forming process, it is revealed that the Laoshan uplift is an old uplift formed in Caledonian period. It was a stable platform in Hercynian. In the Indosinian period, the northern foreland basin was probably a foreuplift flexural belt, formed on an anticline with increasing amplitude. The early Yanshanian fault anticline was a reformed fault anticline. The uplifting was basically stopped in middle Yanshanian stage. The uplifting and denudation happened in late Yanshanian-early Himalayan period, and local residual depressions developed. The overall subsidence began in late Himalayan. Combined with the analysis of oil and gas geological conditions, it is considered that the Gaoshi stable zone in the south of the Laoshan uplift is a favorable region for Marine oil and gas exploration, and the lower structural layer from Sinian to Silurian is weak in deformation and transformation. It should be also a favorable layer for oil and gas exploration.
LEI Baohua, ZHANG Yinguo, WANG Mingjian, CHEN Jianwen, LIANG Jie, WANG Wenjuan
doi: 10.16562/j.cnki.0256-1492.2021101201
Marine Geology & Quaternary Geology. 2022, 42(2): 131-143
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Facies evolution and its controlling factors of the Pinghu Formation in the Kongqueting area of Xihu Depression, the East China Sea
The East China Sea Shelf Basin contains a huge amount of petroleum resources and the Pinghu Formation is one of the major exploration targets. However, the Kongqueting area has rarely been researched, and few studies have been made to sedimentary facies evolution and its controlling factors. Based on drilling and 3D seismic data, microfacies of the Pinghu Formation are carefully described in this paper and the controls of global sea level fluctuation, regional tectonics, paleoclimate, and paleogeography over the facies distribution patterns discussed. The Lower Pinghu Formation is dominated by tidal flat facies, and the braided river delta facies only appeared in some places near uplifts. By contrast, the Middle and Upper Pinghu Formations are dominated by deltaic deposits of braided rivers. Relative sea level falling, as a joint result of global sea level change and regional tectonics, resulted in the progradation of braided river delta towards offshore. Meanwhile, the high concentration of CO2 in the atmosphere during the Middle and Later Pinghu periods caused a sharp increase of erosion. Enormous sediments provided by the source areas were transported into the Xihu Depression, which accelerated the progradation of braided river delta into the sea. In addition, the paleogeographic framework during the Middle to Lower Pinghu Periods were characterized by many fault-controlled sags, which limited the expansion of braided river delta. These sags were filled by sediments in Middle Pinghu Period, and turned to tidal flat in Later Pinghu Period, which also helped the expansion of deltaic deposits of the Upper Pinghu Formation.
WU Feng, REN Peigang, TAN Mingxuan, ZHANG Furong, MA Haoran
doi: 10.16562/j.cnki.0256-1492.2021052401
Marine Geology & Quaternary Geology. 2022, 42(2): 119-130
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An experimental study on visual detection of hydrate-bearing sediments based on ERT
Reservoir evaluation of gas hydrate based on electrical response, as a key mean to discriminate natural gas hydrate and estimate its resource potential, plays an important role in the exploration and development of natural gas hydrate. The physical simulation experiment for gas hydrate formation in sediments was carried out in this paper to detect the morphology of dispersed hydrate and massive hydrate based on electrical resistivity tomography during the formation of hydrate. The resistivity responses of the two gas hydrate morphology were carefully studied. The results show that the high resistivity of dispersed hydrate has a scattered distribution pattern whereas the high resistivity of massive hydrate distributed in a concentrated pattern. The free gas in sediments may cause the position deviation of massive hydrate. The resistivity response characteristics of dispersed hydrate and massive hydrate change largely. Compared to the dispersed hydrate, the resistivity of massive hydrate increases rapidly with the formation of hydrate.
ZHAO Jinhuan, LIU Changling, ZOU Changchun, CHEN Qiang, MENG Qingguo, LIU Yang, BU Qingtao
doi: 10.16562/j.cnki.0256-1492.2021060901
Marine Geology & Quaternary Geology. 2021, 41(6): 206-212
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Characteristics of the recently bedrock hydrocarbon reservoir in China Seas and future exploration directions
Great breakthroughs have been made recently in the exploration of hydrocarbon in bedrock reservoirs in China Seas, such as the Bozhong 19-6 condensate gas reservoir, the Yongle 8-3-1 bedrock oil and gas reservoir and the Bozhong 13-2 oil and gas field, which prove that bedrock oil and gas reservoirs have great potential in offshore China. Up to now, many high-yield bedrock oil and gas fields have been found in the Bohai Basin, Beibu Gulf Basin, Qiongdongnan Basin and Pearl River Mouth Basin. The bedrock hydrocarbon reservoirs in China's sea areas are characterized by wide distribution, multiple layers in vertical sequence, changing lithology and multiple types. As observed, there are four sets of major reservoirs: the Precambrian metamorphic rocks and migmatitic granite, the Paleozoic carbonate rocks, the Mesozoic volcanic rocks and granite intrusions and the Mesozoic clastic sequences, among which the Precambrian metamorphic rocks and Mesozoic granite intrusions dominate. The bedrock oil and gas reservoir is the kind of bedrock reservoir filled by later generated hydrocarbons, and their formation is controlled by many factors, such as source rocks, tectonic activities, reservoir properties and sealing conditions. On the basis of previous researches, it is suggested that the future exploration of bedrock oil and gas reservoirs in China's sea areas should focus more on the following six aspects: the residual mountains in the Bohai basin; the local uplift in the northeast of the eastern depression of the North Yellow Sea Basin; the uplifting belt of the South Yellow Sea Basin; the low uplift in the East China Sea shelf basin; the Weixi 'nan Sag in the Beibu Gulf Basin, the Huizhou Sag in the Pearl River Mouth Basin and the Songnan Low Uplift in Qiongdongnan Basin; and the Zhongjiannan Basin and Wan 'an Basin in the southern South China Sea.
WANG Jianqiang, LIANG Jie, CHEN Jianwen, ZHANG Yinguo, ZHAO Qingfang, DONG Hepin, LI Shuanglin, SUN Jin
doi: 10.16562/j.cnki.0256-1492.2021031201
Marine Geology & Quaternary Geology. 2021, 41(6): 151-162
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Forty years development of marine geology in China: Evidence from scientometrics
Modern marine geology was initiated in 1949 in China right after the founding of the People’s Republic. It has experienced a long terms of data accumulation. However, since the Government adopted the policy of reform and opening-up in late 1970s, the marine geology in China has made great progress and rapid development and become an independent scientific discipline. Based on the analysis on all the literatures published in the journal of "Marine Geology and Quaternary Geology", we made a brief evaluation of the past 40 year development of marine geology in China in this paper by means of scientometrics approaches. Several indicators were extracted through key word frequency statistics, co-word analysis, and knowledge graphs. The research results suggest that: (1) In the past 40 years, the number of new key words in all articles and the annual red point factor (RPF) have remained stable, indicating that the rapid development of marine geology is a complete process. And this trend will continue for 15-20 years or more; (2) According to the "high-frequency key word set", the research hot areas of Chinese marine geology remain with China Seas, the western Pacific, and the parts of polar oceans. The hot fields include sedimentology and environment, geochemistry and bio-geology, structural geology, Quaternary geology, petroleum geology of China offshore basins, paleoclimate and global changes, etc.; (3) According to the "burst key words", the frontiers of marine geology research are focused on new energy resources dominated by natural gas hydrates, western Pacific geodynamics related to plate subduction, and the deep oil and gas accumulated in the Mesozoic and Paleozoic. In addition, the resources and environment and the tectonics of Indian Ocean ridge are also the interests of researches. The development of all disciplines will follow a cyclical process from accumulation to explosion and then to maturity. In the past 40 year history of marine geology in China, it is regrettable that no turning point has been observed so far. To consider the development of earth sciences as a whole, the continuous expansion of research areas is doubtlessly the basis for the development of disciplines. And the adoption and application of new technology and updated survey methods remain the keys to the development. To observe all branches of marine geology in China, both research hot fields and research frontiers appear alternately. So, the development model from frontiers to hot fields and finally to basic knowledge is worthy of further discussion.
WANG Shengjie, ZHOU Lijun, SUN Ping
doi: 10.16562/j.cnki.0256-1492.2021110601
Marine Geology & Quaternary Geology. 2021, 41(6): 1-14
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Characteristics of marine gas hydrate reservoir and its resource evaluation methods
To accurately make resource evaluation is the prerequisite for development of natural gas hydrate resources, and the correct understanding of the characteristics of gas hydrate reservoir is the basis for such evaluation. The content and occurrence of gas hydrate are closely related to and affected by reservoir properties. The occurrence forms of gas hydrate, which includes pore-filling and fracture-filling, mainly depends on the nature and size of pores, fractures and other accumulation spaces in the marine sediments. Different types of hydrate reservoirs have different physical property response characteristics, which directly affects the accuracy of marine gas hydrate resource evaluation. The principles, evaluation parameters and applicability of the existing natural gas hydrate resource evaluation methods are different, and the occurrence type of hydrate is not considered. Based on the previous work, this paper puts forward a new method of "Detail Resource Evaluation" and "Precise Resource Evaluation" for marine natural gas hydrates. The "Detail Resource Evaluation" method based on small panel is suitable for the evaluation of pore-filled hydrate reservoir with rare drilling and dense geophysical survey network in favorable block; The "Precise Resource Evaluation" method based on the concept of "hydrate abundance in reservoir" is applicable to the accurate evaluation of small-scale hydrate orebody with dense well pattern in the well field, and can effectively improve the accuracy of the evaluation of fracture- filled types (e.g. massive, vein and nodule) hydrate resources.
LIU Changling, SUN Yunbao
doi: 10.16562/j.cnki.0256-1492.2021082401
Marine Geology & Quaternary Geology. 2021, 41(5): 44-57
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Stratigraphic classification and sedimentary evolution of the late Neogene to Quaternary sequence on the Central Uplift of the South Yellow Sea
The Core of CSDP-2, which is more than 2800 m long, was retrieved from the Central Uplift of the South Yellow Sea, of which the Mesozoic-Paleozoic strata of the core have become a hot topic under research. However, research results of the uppermost sequence, 592 m in thickness made up of unconsolidated loose sediments, have not yet been reported so far. We have carried out paleomagnetic measurements, optically stimulated luminescence (OSL) dating, identification of benthic foraminifera and analyses of sedimentary facies for the sequence, in order to make its stratigraphic classification and reveal its history of sedimentary evolution. The results indicate that the 592 m- thick sequence came into being about 5.2 Ma, with its Quaternary bottom boundary at ~227.91 m of 2.59 Ma, the Lower and Middle Pleistocene boundary at ~65.23 m of 0.78 Ma, and the Middle - Upper Pleistocene boundary at 47.34 m of 128 ka, and covered by the Upper Pleistocene, which could be further subdivided into several sedimentary intervals formed during MIS 5, MIS 4, MIS 3 and MIS 1, while the MIS 2 deposits are missing. Also the results demonstrate that the denudation took place on the Central Uplift during Neogene and came to an end at ~5.2 Ma, followed by the deposition of fluvial deposits from ~5.2 to ~1.7 Ma, which was ceased as the first marine transgression took place in the region since Cenozoic presumably due to subsidence of the Zhe-Min Uplift. From ~1.7 to ~0.83 Ma, there was an alternation of tidal-flat and coastal deposits, and then from ~0.83 to the present the marine environments during high sea-level stands of the interglacial times were close to the marine environment of today in the region, due to the further subsidence of the Zhe-Min Uplift. On the western shelf of the South Yellow Sea, there was a cold water mass during MIS 5, which is broader than that of nowadays, and fluvial, deltaic, fluvial and coastal to inner-shelf environments prevailed successively during MIS 4, early MIS 3, late MIS 3 to MIS 2, and MIS 1. The sedimentary sequence was primarily controlled by tectonic subsidence and sea-level changes, and the sedimentation rates decreased evidently from the Holocene deposits to the Pleistocene and to the whole sequence, owing to the incompleteness of the older sediments comparing to the younger ones. Especially the pre-Late Pleistocene strata are marked by distinct erosion. The results of this study have provided new evidence for better understanding the evolution of sedimentary environments and the formation mechanism of strata in the western South Yellow Sea shelf since late Neogene.
LIU Jian, DUAN Zongqi, MEI Xi, LIU Qingsong, ZHANG Xunhua, GUO Xingwei, WU Zhiqiang, WANG Hong, WANG Feifei, CHEN Bin, ZHANG Xin, AN Yuhui
doi: 10.16562/j.cnki.0256-1492.2021101701
Marine Geology & Quaternary Geology. 2021, 41(5): 25-43
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Controlling factors and research prospect on creeping behaviors of marine natural gas hydrate-bearing-strata
Creeping of HBS is a common behavior of hydrate-bearing strata in the process of gas production and has great impact on the occurrence and development of engineering geohazards. In this paper, we summarized the main failure modes of HBS based on the investigation of a large number of literatures. Then the research thoughts and strategies on strata creeping behaviors during hydrate exploitation are comprehensively discussed, based on the key scientific issues expounded. Afterwards, a multi-scale creeping detection and characterization approach for HBS is put forward, together with its future research trends. It is supposed that creeping behaviors of HBS during gas extraction are the result of combination of hydrate distribution and its dissociation-induced changes in multi-physical fields such as phase transformation, heat exchange, seepage, and stress evolution. The current constitutive models for conventional soils are not effective enough to reflect such a complex dynamic multifield, multiphase and multicomponent coupling effect, which are doubtlessly inadaptable for evaluating the geotechnical issues during hydrate exploitation in the case of northern South China Sea. For this reason, a multi-scale detection and characterization system needs to be established to analyze the dynamic damage behaviors of HBS during hydrate production, which consists of the molecular scale, nano-to-micro scale, core scale, pilot scale, and field scales techniques. Using the sediments collected from the HBS at the northern South China Sea, the control mechanisms of different geological and engineering parameters on hydrate-bearing strata creeping should be quantitatively modeled.
WU Nengyou, LI Yanlong, LIU Lele, WAN Yizhao, ZHANG Zhengcai, CHEN Mingtao
doi: 10.16562/j.cnki.0256-1492.2021092201
Marine Geology & Quaternary Geology. 2021, 41(5): 3-11
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Seafloor hydrothermal system and its magmatic setting in the western Pacific back-arc basins
The study of seafloor hydrothermal system and its magmatic setting can provide effective research support for understanding the material and heat exchange processes across the multi-spheric fluid-solid interfaces in the western Pacific. In order to reveal the magmatic activities, mineral deposition and environmental responses to plate subduction, the magmatic setting of Okinawa Trough hydrothermal systems, hydrothermal plume of Manus basin, isotopic composition of sulfide and basalt in back arc basins and mid-ocean ridges are carefully studied in this paper. The petrographic, mineralogical, major and trace elements, and isotopic composition for basalt, andesite, trachyandesite, dacite, rhyolite and their basic magmatic enclaves near the Okinawa Trough hydrothermal field have been carried out, whereas the hydrothermal plume and seawater measurement in PACMANUS and Desmos hydrothermal fields of the Manus basin studied. The results have successfully revealed the magmatic mixing process and time scale, the deep magmatic chamber and magma evolution process, the contribution of magma to the hydrothermal system in the Okinawa Trough as well as the influence of subduction serpentine on magmatic activity in the southern Ryukyu subduction zone. Melt inclusions are used as the mean to study the evolution of the back-arc basin magma, and the new evidence of the source of basaltic magma in the Okinawa Trough. The origin of iron, copper and zinc in the sulfide and basalts of the mid-ocean ridges and the back-arc basins, and the iron, copper, and zinc isotopic fractionation during sulfide formation and magmatic activity are discussed. The physical and chemical spatial pattern and material composition characteristics of the hydrothermal plume have been defined. It seems that the diffusion depth of the hydrothermal plume is affected by local seawater depth and bottom current, and the concentration anomaly of the dissolved Fe may remain for longer time than dissolved Mn during lateral plume dispersal. In the future, non-traditional stable isotopes and volatile analytical technology should be adopted for further understanding of the relationship between hydrothermal activity and magmatism under plate subduction environment taking the western Pacific as a research case so as to know more about the seafloor hydrothermal system and its ore-forming processes.
ZENG Zhigang, ZHANG Yuxiang, CHEN Zuxing, LI Xiaohui, QI Haiyan, WANG Xiaoyuan, CHEN Shuai, YIN Xuebo
doi: 10.16562/j.cnki.0256-1492.2021070101
Marine Geology & Quaternary Geology. 2021, 41(5): 12-24
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Marine geology and Quaternary geology: A combination
The present journal is unique in its combination of two prominent science disciplines: Marine geology and Quaternary geology. To celebrate its 40th anniversary, the paper reviews the history of joint development of the two disciplines in China, with a discussion on its prospects in the future.
WANG Pinxian
doi: 10.16562/j.cnki.0256-1492.2021072601
Marine Geology & Quaternary Geology. 2021, 41(5): 1-2
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Provenance evolution since Middle Holocene of the sediments on the East Siberian shelf: Evidence from elemental geochemistry
The Arctic region is very sensitive to global climate change. It is a key area in the world to the study of paleoenvironmental and paleoclimatic changes. The East Siberian Sea (ESS) is one of the important marginal seas in the Arctic region. Study of the sediment provenance of the ESS shelf is essential to the overall understanding of the Arctic environmental and climatic changes. Based on the analyzing results of the major, trace and rare earth elements from the core of LV77-36, this paper described the change patterns of concerned indices with time, discussed the variation of detrital components in the ESS sediments since Middle Holocene, and finally, revealed the response of provenance evolution to paleoenvironment changes. The results show that since Middle Holocene, the sediments of the core LV77-36 are mainly coming from the suspended materials carried by the Lena, Indigirka, Yana and Mackenzie rivers, in addition to the coastal erosive materials from the Siberian platform and New Siberian Islands. According to the Comparison with other paleoclimatic parameters, it is found that the changes of sea ice and ocean currents have important effects on the dispersion and deposition of sediments on the East Siberia shelf. In Late Holocene, due to the increase in sea ice in the Chukchi Sea, the weakening of the Siberian coastal current and the strengthening of the Beaufort circulation, the material contributed by the North American end member increased slightly compared to the Middle Holocene sediments.
FANG Xiaorong, HU Ningjing, DOU Ruxi, ZHANG Ying, ZHANG Hui, LIU Jihua
doi: 10.16562/j.cnki.0256-1492.2020122701
Marine Geology & Quaternary Geology. 2021, 41(4): 60-73
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Rethinking on shallow sedimentary sequence and its evolution of the Xiyang tidal channel in the Radial Sand Ridge Field, South Yellow Sea
Since the Late Quaternary, both the Yellow River and Changjiang River entered into the South Yellow Sea flowing through the middle Jiangsu coast. As a result, a series of sediments have been deposited in this area controlled by the river-sea interactions. The Radial Sand Ridge Field (RSRF) off the middle Jiangsu coast has been formed after the Holocene transgression. The Xiyang tidal channel in the northwestern RSRF is constrained by the tidal flat coast and tidal ridges. It is located in the transition zone between the northern Abandoned Yellow River delta and southern modern Changjiang River delta. Therefore, it becomes the important window area to reveal the sedimentary sequence formed in the coast and continental shelf under the active interactions between different large rivers during the Late Quaternary. As to the upper strata with the depth less than 60 m below the current mean sea-level in the Xiyang tidal channel, there are still different viewpoints on its sedimentary sequence, chronology framework and evolution, while the concerned studies are still pretty limited. Recently, the results of further Late Quaternary stratigraphic correlations and synthesis study on shallow seismic profiles showed that, (1) Due to disordered dating results and improper correlation of terrigenous stiff mud layers, the chronology framework of Xiyang upper strata built previously based on core 07SR01 and Y1 is incorrect, the main part of the upper strata including two sedimentary cycles are the Late Pleistocene deposits and the stiff mud layer of the Last Glacial Maximum is often missing due to the tidal scouring, the thickness of surficial Holocene sediments are generally less than 10 m in the submerged sand ridges, and extensively less than 5 m in other places, or even zero in some places; (2) The shallow seismic unit 3 (U3) only steadily located in the northwestern part of the Xiyang tidal channel indicates the southern margin of the old Yellow River delta developed during MIS 3, and the middle Jiangsu coast in which the Xiyang tidal channel is located was probably influenced deeply by the old Yellow River sediments since the Late Pleistocene, however it is still necessary to recover a new sedimentary core in the key position of northwestern part, plus further study and verification based on the new core and other acquired shallow seismic profiles and cores in the southeastern part should be done. Thus, this paper proposed the further study plan as follows, based on the 3D visualization of the seismic sequence framework, the spatial characteristics of the seismic units and main reflection interfaces would be extracted. Furthermore, combined with the sedimentology and chronology studies of the existing and designed cores, the reliable chronology framework would be set up expectedly, and the provenance from large rivers would be identified. Applying the sequence stratigraphy method, referencing the adjacent published core data, it is targeted to ascertain the shallow sedimentary sequence in the Xiyang tidal channel, and to reveal its evolution.
XIA Fei, ZHANG Yongzhan, LIU Dezheng
doi: 10.16562/j.cnki.0256-1492.2021033101
Marine Geology & Quaternary Geology. 2021, 41(4): 13-26
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Environmental magnetic characteristics and influencing factors on the west coast of Fildes Peninsula, Antarctica
The unique environmental system of the Antarctic ice-free region has been widely studied in recent decades, and environmental magnetism is doubtlessly the method most commonly used in the study. In the year of 2015, a 26 cm long core was collected by the authors from the west coast of the Antarctic peninsula for environmental magnetism, granularity, 210Pb and stable carbon isotope testing and analysis. The bedrock of the coast is dominated by andesitic basalt, so the sediments of the core samples are high in magnetic minerals in general, that resulted in high magnetism. The average susceptibility (χlf) is about 1597×10−8 m3·kg−1, almost 3~4 times higher than the beach magnetic susceptibility. The magnetic minerals mainly consist of ferromagnetic particles (magnetite) with small amount of antiferromagnetic particles (hematite). The vertical changes in 210Pb and granularity data suggest that the sediment particle size is too fine for water movement, and therefore, the movement of pore water is weak. Under such a circumstance, the fine magnetic mineral grains are easily to be preserved. With the increase in depth, the sediments gradually become coarser, and the movement of water is thus enhanced. Plus the influence of biological organic dissolution, magnetism parameters of the lower part of the core is decreased accordingly.
TANG Huaineng, WANG Yonghong, HUANG Qinghui
doi: 10.16562/j.cnki.0256-1492.2020092001
Marine Geology & Quaternary Geology. 2021, 41(4): 1-12
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