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1.
《山地科学学报》2020,17(8):2023-2034
Desert-oasis ecotones are boundary areas between oases and desert ecosystems.Large efforts to control sediment and stabilize these boundaries depend on understanding sedimentary processes,especially aeolian transport and deposition.Previous studies on aeolian sediment deposition have focused primarily on a single land surface type or a single engineering approach.Few studies have considered deposition in a multi-layer oasis protective system.A complete oasis protective system consists of an outer bare sand area,a sand barrier zone,a shrub and herbaceous plant zone,and a farmland shelter zone.This study used sedimentary analysis to quantify grain-size characteristics in samples from the four land surfaces under different types of weather conditions in the Gelintan oasis of the Tengger Desert,the fourth largest desert in China.The results showed that aeolian sediment deposition decreased from the outer bare sand area through the oasis protective system and into the interior.The four land surface types showed significant differences in deposition volume(P 0.05).Deposited sediment showed gradual decrease in dominant grain-size from sand to silt,but sediment deposited during dust weather contained a larger coarse-grained fraction.From the outer desert to the inner oasis,transport mechanisms shifted from saltation(sand) to suspension(silt and smaller) in non-dust weather.During dust weather,deposition primarily occurs from near-surface aeolian sand transport with saltation.Sediment sorting decreased from exterior to interior zones of the protective system while skewness and kurtosis showed no significant change(P 0.05).These results can help inform strategies for stabilizing and protecting desert-oasis ecotones in this region and other localities. 相似文献
2.
The distributions of thickness of unconsolidated Quaternary sedimentary layers in Jiaozhou Bay and Qingdao offshore area were studied by using 1079-km high-resolution shallow seismic profiles and drilling core data, and the factors controlling the Quaternary evolution were discussed. The results show that such thickness distributions resulted from the coactions of geologic structures and marine hydrodynamic conditions since the Holocene. The geologic structures controlled the slope deposit, proluvial and fluvial fillings since the late Pleistocene. Holocene marine hydrodynamics eroded away sediments at the bay mouth, and tides carried these eroded materials to the sides of the bay mouth and released them there, forming channel-ridge-alternating geomorphic features. During transgressive processes, the sea level rose rapidly, and insufficient sediment supply and tidal actions yielded the relict sediments in the east of Qingdao offshore area. 相似文献
3.
ＩＮＴＲＯＤＵＣＴＩＯＮＳｔｕｄｙｏｆａｇｒｅａｔｑｕａｎｔｉｔｙｏｆｓｅｄｉｍｅｎｔｓａｎｄｈｉｇｈ ｒｅｓｏｌｕｔｉｏｎｓｅｉｓｍｉｃｐｒｏｆｉｌｅｓ (3 .5ｋＨｚ)ｄａｔａｃｏｎ ｆｉｒｍｅｄｔｈｅｅｘｉｓｔｅｎｃｅｏｆａｌａｒｇｅａｒｅａｏｆｍｕｄｄｙｓｅｄｉｍｅｎｔｓｗｈｏｓｅｄｉｓｔｒｉｂｕｔｉｏｎ ,ｆｏｒｍａｔｉｏｎｅｎｖｉｒｏｎｍｅｎｔａｎｄｏｒｉｇｉｎｈａｄｂｅｅｎｓｔｕｄｉｅｄｂｙｖａｒｉｏｕｓｒｅｓｅａｒｃｈｅｒｓ (Ｌｉｕｅｔａｌ.,1 987;ＰａｒｋａｎｄＫｈｉｍ ,1 990 ;Ａｌｅｘａ… 相似文献
4.
Seismic stratigraphic analysis of 150 km of high-resolution seismic profiles (GEO-PULSE and 3.5 kHz) obtained along the muddy coast off Taishan, Guangdong provided valuable information on the offshore Quaternary stratigraphy, tectonics, sedimentary evolution, and environmental and engineering geology of this area. The following late Quaternary stratigraphic sequences were mapped. (1) Pleistocene alluvial silty sand and shallow marine clay; (2) coarse fluvial channel sand; (3) nearshore and bay clayey sediments. The incision of fluvial channels occurred in two stages: dttring the Late Pleistocene and at the beginning of the Holocene. The Pleistocene fluvial channels have been filled by coarses and overlain by more than 10 m of late Pleistocene clay and 20 - 30 m of Holocene clay. The coastal area is dissected by two major fault systems: the first group strikes ENE-WSW and controls the evolution of the adjacent Quaternary basin, while the second one trends NNE-SSW. These fault systems must be taken into account in any coastal engineering considerations. In addition, both granitic and metamorphic basements were recognized. 相似文献
5.
近几年来,多个大型油气发现使得毛塞几比盆地成为国际油气勘探的热点区域。基于地震资料和钻测井资料系统开展了沉积相以及沉积模式研究、储层物性分析、烃源岩评价以及成藏体系分析工作。研究结果表明:①盆地中南部外陆架广泛发育多期强制海退三角洲沉积体系,受基准面旋回控制,强制海退三角洲顶积层遭受剥蚀,砂体被搬运到三角洲前部,形成强制海退砂,砂体在陆架边缘附近广泛分布;陆坡类型控制了深水扇差异分布模式,南部断控型陆坡控制了深水扇的分布,深水扇主体发育在陆坡坡脚,距离陆架边缘较近,北部平缓型陆坡下重力流搬运较远,深水扇主体远离陆架边缘,据此建立了南部断控型陆坡控砂模式和北部缓坡型陆坡富砂模式。②外陆架强制海退三角洲和北部缓坡型深水扇储层条件好,测试产能高,受胶结作用和滑塌碎屑影响,南部陡坡型深水扇储层物性差。③油源对比表明,油气主要来自下白垩统阿普第阶-阿尔比阶与上白垩统赛诺曼阶-土伦阶海相烃源岩,阿普第阶-阿尔比阶烃源岩以Ⅱ2型干酪根为主,主要生气;赛诺曼阶-土伦阶海相烃源岩以Ⅰ型干酪根为主,主要生油。④研究区发育3套有利成藏体系,分别为阿尔比阶陆架边缘成藏体系、阿尔比阶-土伦阶陆坡坡脚成藏体系以及赛诺曼阶陆坡远端成藏体系,其中陆架边缘成藏体系与陆坡远端成藏体系勘探潜力更大,是下一步勘探的重点。 相似文献
6.
Clay minerals of surface sediments in the South China Sea (SCS) are analyzed with X-ray diffraction, and their transport is
explored with a grain size trend analysis (GSTA) model. Results show that clay mineral types in various sedimentary environments
have different sediment sources and transport routes. Sediments in the northern SCS (north of 20°N) between the southwest
of Taiwan Island and the outer mouth of the Pearl River have high contents of illite and chlorite, which are derived mainly
from sediments on Taiwan Island and/or the Yangtze River. Sediments from the Pearl River are characterized by high kaolinite
and low smectite content, and most are distributed in the area between the mouth of the Pearl River and northeast of Hainan
Island and transported vertically from the continental shelf to the slope. Characterized by high illite content, sediments
from Kalimantan Island are transported toward the Nansha Trough. Sediments from Luzon Island are related with volcanic materials,
and are transported westwards according to smectite distribution. On the Sunda Shelf, sediments from the Mekong River are
transported southeast in the north while sediments from the Indonesian islands are transported northward in the south. Ascertaining
surface sediment sources and their transport routes will not only improve understanding of modern transportation and depositional
processes, but also aid paleoenvironmental and paleoclimatic analysis of the SCS. 相似文献
7.
KAN Guangming MENG Xiangmei WANG Jingqiang CAO Guolin LI Guanbao LIU Baohua ZHI Pengyao 《中国海洋大学学报(英文版)》2022,21(1):91-100
To accurately characterize the shear wave speed dispersion of seafloor sediments in the northern South China Sea,five types of sediments including silty clay,clayey silt,sandy silt,silty sand,and clayey sand were selected,on which the measurements of the shear wave speed at 0.5-2.0 kHz and related physical properties were performed.Results reveal that the shear wave speed of sediments increases as the frequency increases,and the dispersion enhanced in the sediments in the order of silty clay,clayey silt,sandy silt,silty sand,and clayey sand,at a linear change rate of 0.727,0.787,3.32,4.893,and 6.967 m s?1 kHz?1,respectively.Through regression analysis,linear and logarithmic regression equations for the correlation between shear wave speed and frequency were established for each sediment type and the determination coefficients of regression equations indicate that the correlation is closer to a logarithmic relationship.The Grain-Shearing(GS)and Biot-Stoll models were used to calculate the shear wave speed dispersion of the five sediment types,and the comparison between theoretical prediction and measured results of shear wave speeds shows that the GS model can more accurately describe the shear wave speed dispersion characteristics of these sediments in the frequency band of 0.5-2.0 kHz.In the same band,the predictions obtained by using the Biot-Stoll model are significantly different from the measured data. 相似文献
8.
Desertization of the continental shelf of China in the later stage of Late Pleistocene 总被引：1，自引：0，他引：1
In the later stage of Late Pleistocene, global climate entered into the climax period of Würm when temperature decreased remarkably
and glaciers developed. Information from the East China Sea also confirm that the sea level fell by at least 130 m at that
time (Emery, 1968). The Bohai Sea and Yellow Sea at the climax period were totally exposed, while the East China Sea and South
China Sea shelf regions were exposed partly. The exposed shelf area exceeded 1 million km2 and became a salty desert where land plants could not survive. Such were the conditions which led to the desertization of
the shelf region.
Eolation was the major exogenetic force not only on land but also on the shelf region in the ice age. At the climax period
of Würm, the northern part of China developed thick layers of loess deposits. The shelf region at that time had similar climatic
conditions and sediments. Because the shelf region was not protected by vegetation in the ice age, intensive wind storms remoulded
the primarily deposited strata to produce new sedimentary differentiation and new series of land sediments. Shallow-layer
profiler records indicated the existence of many land sediment types, including dunes, dune-chains, desert bodies, thick layers
of repose angle sediments and desertization derivatives.
New data available show the shelf region adjoining China can be divided into six regions of desertization and its derivatives.
Contribution No. 1846, from the Institute of Oceanology, Acadernia Sinica.
Project sponsored by the National Natural Science Foundation of China. 相似文献
9.
Zhou Fugen 《中国海洋湖沼学报》1989,7(3):274-282
Since the last rising of sea level, two branches of the Kuroshio, the Huanghai (Yellow Sea) coastal current (HCC; mainly cold
water mass) and the Changjiang River outflow have controlled the modern dynamic deposition in the East China Sea. There are
three depositing areas on the sea-bed under the above currents: a relict sand area un der the Taiwan Warm Current and the
Huanghai Warm Current at the south-eastern area, the about 60 km2 round mud bank under the Huanghai Coastal Current at the northern area and the large subaqueous delta of mainly fine sand
and silt under the Changjiang discharge flow in its estuary and the large narrow mud bank under the Zhejiang-Fujian Coastal
Current, another round mud bank under the Changjiang discharge flow off Hangzhou Bay. The relict sand area has a coarsesand
block under the Taiwan Warm Current bypassing Taiwan at the northern part of the island.
The two round mud banks were formed in relatively static states by an anticlockwise converging cyclonic eddy. The coarsesand
block was formed by a clockwise diverging cyclonic eddy. This new dynamic deposition theory can be used to explain not only
the dynamic deposition process of clay, but also the patchy distribution of sediments on the shelves of the world ocean s. 相似文献
10.
Correspondence analysis and fuzzy C-means cluster methods were used to divide the stratigraphy of heavy mineral assemblages,
and the sediment sources and depositional dynamics of the environment reconstructed. The assemblages were taken from marine
sediments from the late Pleistocene to the Holocene in Core Q43 situated on the outer shelf of the East China Sea. Based on
the variable boundaries of the mineral assemblage at 63 and 228 cmbsf (cm below sea floor), the core might have previously
been divided into three sediment strata marked with units I, II and III, which would be consistent with the divided sediment
stratum of the core using minor element geochemistry. The downcore distribution of heavy minerals divided the sedimentary
sequence into three major units, which were further subdivided into four subunits. The interval between 0 and 63 cmbsf of
the core (unit I), which spans the Holocene and the uppermost late Pleistocene, is characterized by a hornblende-epidote-pyroxene
assemblage, and contains relatively a smaller amount of schistic mineral and authigenic pyrite. In comparison, the interval
between 63 and 228 cmbsf (unit II), is representative of the Last Glacial Maximum (LGM), and features a hornblende-epidote-magnetite-ilmenite
assemblage containing the highest concentrations of heavy minerals and opaque minerals. However, the interval between 228
and 309 cmbsf (unit III), which spans the subinterglacial period, is characterized by a hornblende-authigenic-pyrite-mica
assemblage. Relative ratios of some heavy minerals can be used as tracers of clastic sediment sources. The lower part of the
sediment core shows the highest magnetite/ilmenite ratio and relatively high hornblende/augite and hornblende/epidote ratios.
The middle core shows the highest hornblende/augite and hornblende/epidote ratios, and the lowest magnetite/ilmenite ratio.
The upper part exhibits a slightly higher magnetite/ilmenite ratio, and also the lowest hornblende/augite and hornblende/epidote
ratios. The distribution of the mineral ratio is consistent with stratigraphic division in heavy mineral data using correspondence
analysis and fuzzy C-means clustering. Variations in heavy mineral association and mineral ratio in core Q43 revealed changes
in provenance and depositional environment of the southern outer shelf of the East China Sea since the late Pleistocene, well
corresponding to interglacial and glacial cycles. 相似文献
11.
Correspondence analysis and fuzzy C-means cluster methods were used to divide the stratigraphy of heavy mineral assemblages,and the sediment sources and depositional dynamics of the environment reconstructed.The assemblages were taken from marine sediments from the late Pleistocene to the Holocene in Core Q43 situated on the outer shelf of the East China Sea.Based on the variable boundaries of the mineral assemblage at 63 and 228 cmbsf (cm below sea floor),the core might have previously been divided into th... 相似文献
12.
对分布于临沂一带沂河与沭河沿岸沙带的展布形态与沉积层理进行研究,认为该沙带属于古洪水期滞留沉积物(SWD),并非以往认为的风沙成因(寒亭组)。为了获取滞留沉积物的形成年龄,采用光释光测年(OSL)方法,首次获得对应沉积物年龄为0.8ka,1.2ka,结合相关历史时段的洪水记录,综合分析后,认为该滞留沉积物记录了发生在唐宋时期的两次历史洪水。 相似文献
13.
高邮凹陷古近系戴南组扇三角洲沉积体系及其沉积相模式 总被引：1，自引：0，他引：1
扇三角洲是苏北盆地高邮凹陷戴南组较为发育的一种沉积类型,集中分布在凹陷南部陡坡带一侧,是该区一个重要的勘探领域。根据岩芯、测井、地震、粒度等资料,对高邮凹陷古近系戴南组扇三角洲的沉积特征进行了研究,建立了高邮凹陷戴南组的沉积相模式。根据单井沉积相、连井沉积相分析以及地震剖面反射特征和砂地比图综合分析,确定了戴南组各亚段沉积相的平面展布,编制了戴南组各亚段沉积相分布图。结果表明:高邮凹陷南部陡坡带地形陡,存在扇三角洲发育的条件,也存在反映浅水环境的岩性特点,成分成熟度和结构成熟度低反映了近物源的条件,还发现反映牵引流和重力流共存的沉积构造特点;从地震反射特征上看,反射结构不稳定,并发现向盆地边缘加厚的楔形地震相。在此基础上,重点对戴南组扇三角洲相各微相进行了分析,共划分出扇三角洲平原、扇三角洲前缘和前扇三角洲亚相,并进一步划分出水上分流河道、漫滩沼泽、水下分流河道、分流河道间和席状砂等微相,最后详细阐述了各微相的沉积特征。 相似文献
14.
We analyzed grain size composition to provide information on the types and distributions as well as depositional varieties of marine surface sediments from the area surrounding the Antarctic Peninsula. The samples retrieved from the study area contain gravel, sand, silt and clay. As suggested by bathymetry and morphology, the study area is characterized by neritic, hemipelagic and pelagic deposits. The glacial-marine sediments can be divided into two types, residual paratill and compound paratill, which are primarily transported by glaciers and as ice-rafted debris. Ocean current effects on deposition are more obvious, and the deposit types are distributed consistently with terrain variations. 相似文献
15.
利用岩心、测井、录井、地震等资料,应用层序地层学与沉积学理论,建立博兴洼陷深洼区古近系沙河街组三段中亚段层序地层格架,识别沉积相类型,揭示研究区沙河街组三段中亚段湖底扇砂体的充填期次和规律.结果表明:沙河街组三段中亚段地层划分为2个三级层序,层序内部细分为6个体系域;识别湖底扇中扇、湖底扇外扇、深湖3种沉积亚相,以及辫状水道、水道间、席状浊积岩、远源浊积岩和深湖泥5种沉积微相;总结各沉积微相在岩心、测井、地震上的识别特征;在层序格架内识别各体系域沉积相平面展布规律.此研究对该区下一步油气资源的勘探开发具有指导意义. 相似文献
16.
LIU Jinqing CHEN Xiaoying YIN Ping CAO Ke GAO Fei MENG Yuanku QIU Jiandong LI Meina 《中国海洋大学学报(英文版)》2021,(2)
In this paper, we analyzed the grain size and heavy mineral compositions of 52 surface sediment samples collected from the Kompong Som Bay of Cambodia and the adjacent rivers to depict the marine sedimentary environments and transport processes. Heavy minerals in sediments are dominated by authigenic pyrite, siderite, and tourmaline, with average percentages of 36.52%, 29.02%, and 10.94%, respectively. Two provinces can be divided according to the spatial similarity of minerals. The sediments from Province I, covered by silt grains in the northern bay, are characterized by autogenic pyrite, indicating a weakly reducing environment;whereas in Province II, covered by sand grains in the southern bay, the siderite-tourmaline-authigenic pyrite-zircon-hornblende assemblage occurs, indicating a mild reducing environment and locally oxidizing environment. Most of the sediments in the Kompong Som Bay are introduced from the Preak Piphot River and Srae Ambel River, except that some of them in the south areas come from coastal erosion. Generally, the sediments are difficult to be transported because of the low sediment loads entering the sea and weak hydrodynamic conditions. However, they are transported from the north to the south during the tide ebbing when the hydrodynamic force is much stronger. The sediment distribution and transport patterns are controlled by many factors, including submarine topography, hydrodynamic conditions, the southwest monsoon, land contours, and sediment supply. 相似文献
17.
Qinqin Tang Jinchang Zhang Yingci Feng Jian Li Yantao Yao Jie Sun Wenhuan Zhan 《中国海洋大学学报(英文版)》2018,17(4):763-772
In recent years, infrastructure construction on coral reefs has been increasingly developed. Therefore, the shallow strata stability of coral reefs in the South China Sea should be evaluated. This study aims to investigate the profiles for the shallow strata of coral reefs in the southwest of the Yongshu Reef, particularly in the hydrodynamic marine environment, and to establish a geological model for numerical simulation using Geo-Studio. The shallow strata of the coral reefs include mass gravel, sand gravel, mid-coarse sand, silty sand, fine sand, and reef limestone. The shallow reef slope near the lagoon is similar to a ‘layer cake', in which the side close to the sea is analogous to a ‘block cake'. The simulation results showed that coral reef stability depends on wave loads and earthquake strength and on the physical properties of coral reefs. The factor of safety for the outer reef is greater than 10.0 under static, wave, and seismic conditions; this indicated that the outer reefs were less affected by waves and earthquakes. However, the factor of safety next to the lagoon varied from 0.1 to 5.3. The variation was primarily caused by the thick strata of coral reefs close to the sea(reef limestone, typically with the thickness 10 m and equivalent to a block). The soil and rock layers in the coral reef strata with thicknesses 10 m showed weak engineering geological characteristics. Our findings can provide useful information to future construction projects on coral reefs. 相似文献
18.
Sedimentary sequence and sediment provenance are important factors when it comes to the studies on marine sedimentation. This paper studies grain size distribution, lithological characteristics, major and rare earth elemental compositions, micropaleontological features and ~(14)C ages in order to examine sedimentary sequence and sediment provenance of the core BH6 drilled at the mouth of the Yellow River in Bohai Sea. According to the grain size and the micropaleontological compositions, 4 sedimentary units have been identified. Unit 1(0–8.08 mbsf) is of the delta sedimentary facies, Unit 2(8.08–12.08 mbsf) is of the neritic shelf facies, Unit 3(12.08–23.85 mbsf) is of near-estuary beach-tidal facies, and Unit 4(23.85 mbsf–) is of the continental lake facies. The deposits from Unit 1 to Unit 3 have been found to be marine strata formed after the Holocene transgression at about 10 ka BP, while Unit 4 is continental lacustrine deposit formed before 10 ka BP. The provenances of core BH6 sediments show properties of the continental crust and vary in different sedimentary periods. For Unit 4 sediments, the source regions are dispersed while the main provenance is not clear, although the parent rock characteristics of a few samples are similar to the Luanhe River sediments. For Unit 3, sediments at 21.1–23.85 mbsf have been mainly transported from the Liaohe River, while sediments above 21.1 mbsf are mainly from the Yellow River and partially from the Liaohe River. For Unit 2, the sediments have been mainly transported from the Yellow River, with a small amount from other rivers. For Unit 1, the provenance is mainly the Yellow River catchment. These results help in better understanding the evolution of the Yellow River Delta. 相似文献
19.
The purpose of this study was to assess the effect of long-term cultivation and water erosion on the soil organic carbon （OC） in particle-size fractions. The study site is located at Nihegou Watershed in the Southern Loess Plateau, China. The soil at this site is loess with loose and silty structure, and contains macropores. The results showed that the OC concentrations in sediments and in the particle-size fractions of sediments were higher than those in soils and in the particle-size fractions of soils. The OC concentration was highest in the clay particles and was lowest in the sand particles. Clay particles possessed higher OC enrichment ability than silt and sand particles. The proportions of OC in the silt fractions of soil and sediment were the highest （mean value of 53.87% and 58.48%, respectively）, and the total proportion of OC in the clay and silt fractions accounted for 96% and 98% of the total OC in the soil and sediment, respectively. The loss of OC was highest in silt particles, with an average value of 0.16 Mg ha^-1 y^-1, and was lowest in the sand （0.003 Mg ha^-1 y^-l）. This result suggests that the fine particle-size fraction in the removed sediment may be an important indicator to assess soil OC losses. 相似文献
20.
Type and evolution of landscapes of Nansha Islands 总被引：1，自引：0，他引：1
赵焕庭 《中国地理科学(英文版)》1998,8(2):144-151
ＴＹＰＥＡＮＤＥＶＯＬＵＴＩＯＮＯＦＬＡＮＤＳＣＡＰＥＳＯＦＮＡＮＳＨＡＩＳＬＡＮＤＳＺｈａｏＨｕａｎｔｉｎｇ（赵焕庭）ＳｏｕｔｈＣｈｉｎａＳｅａＩｎｓｔｉｔｕｔｅｏｆＯｃｅａｎｏｌｏｇｙ,ｔｈｅＣｈｉｎｅｓｅＡｃａｄｅｍｙｏｆＳｃｉｅｎｃｅｓ,Ｇｕ... 相似文献