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1.
Clay minerals of 34 sediments collected from the northwestern continental shelf of the East China Sea have been determined by X-ray diffraction analysis. The clay mineral distribution is mainly controlled by the sediment source and the dominant circulation pattern. The predominant clay mineral in our study area is illite comprising more than 67% of the whole clay fraction. The highest concentration of illite (>68%) is found in the southeastern offshore parts beyond the reach of terrigenous input from the Jeju Island. It means that these illites are largely transported by the Kuroshio Current from the South China Sea (SCS). Smectite is highly concentrated in the northwest middle part and in the outer-shelf mud patch. It seems to be due to the high supply of smectite transported from China where fine-grained sediments are discharged from modern and ancient Huanghe (Yellow) River. The relatively high abundant kaolinite is likely derived from the Changjiang (Yangtze) River via the Taiwan Warm Current. In contrast, large amounts of chlorite and high chlorite/kaolinite ratios occur in the northwestern area, reflecting the transportation by the Yellow Sea Coastal Current from the southern Yellow Sea. The discrimination diagrams clearly show that the sediments in the northwestern East China Sea are ultimately sourced from Chinese rivers, especially from the Huanghe River, whereas the sediment in the northeast part might come from the Jeju Island. The muddy sediments of the Changjiang River’s submerged delta have much lower 87Sr/86Sr ratios (0.716 2–0.718 0) than those of the Shandong Peninsular mud wedge (0.721 6–0.724 9), which are supposed to be originated from the Huanghe River, suggesting the distribution pattern of 87Sr/86Sr ratios as a new tracer to discriminate the provenance of shelf sediments in the study area. The 87Sr/86Sr ratios of the outer-shelf muddy sediments ranged from 0.7169 to 0.7216 in a wide range and was between those of the Huanghe River and Changjiang River sediments, suggesting multiple sources of the sediment in the area.  相似文献   

2.
The concentrations of rare earth elements(REEs) in the bulk sediment of Core X2, which was collected from southeastern Hainan Island, were analyzed to investigate the relative contributions of various provenance regions since mid-Holocene. The results show that sediments in Core X2 were primarily derived from Hainan Island with lesser amounts from Taiwan and limited input from the Pearl River. Based on the application of quantitative inversion to model the REE data, the average contributions of river materials from southeastern Hainan Island and southwestern Taiwan to the study area were 68% and 32%, respectively. Furthermore, starting at 4.0 kyr BP, the transport of fluvial sediments from Taiwan to the study region increased due to enhanced hydrodynamics in South China Sea(SCS). These results indicate that the contributions of mountain river materials from Hainan Island and Taiwan to the continental shelf of northern SCS are non-negligible. Furthermore, these results demonstrate that mountain rivers can play an important role in the material cycle of continental margins and may feature a greater impact than large river systems in specific continental shelf areas.  相似文献   

3.
Clay mineral compositions of 199 offshore surface sediment samples collected from the Hangzhou Bay have been analyzed. The clay minerals in the sediments from the Hangzhou Bay are dominated by illite(58.7%, on average), followed by chlorite(20.3%), kaolinite(16.9%) and smectite(4.1%). Two provinces were classified by Q-mode cluster analysis. Class Ⅰ with relatively low amounts of illite and smectite is widely distributed in the Hangzhou Bay, especially concentrated in the top and mouth of the bay, and the northern and southern nearshore areas. Class Ⅱ with comparatively high amounts of illite and smectite is mainly concentrated in the central part of the bay with the water depth of 8–10 m. By comparing clay mineral compositions with the neighbouring regions, we can find that the sediments in the Hangzhou Bay are mainly influenced by the resuspension and repeated deposition of particles from the Yangtze River due to the strong dynamic environment. In particular, the clay fraction of Class Ⅰ is mainly supplied by the Yangtze River, while the sediments of Class Ⅱ are mixture of the clay minerals carried by the Yangtze River and Qiantang River. In general, the distributions of clay minerals in the northern bay are affected by Yangtze River runoff, coastal current and flood tide together, and in the southern they are mainly affected by the Qiantang River runoff and ebb tide.  相似文献   

4.
Mineralogical analysis was performed on bulk sediments of 79 surface samples using X-ray diffraction. The analytical results, combined with data on ocean currents and the regional geological background, were used to investigate the mineral sources. Mineral assemblages in sediments and their distribution in the study area indicate that the material sources are complex. （1） Feldspar is abundant in the sediments of the middle Chukchi Sea near the Bering Strait, originating from sediments in the Anadyr River carried by the Anadyr Current. Sediments deposited on the western side of the Chukchi Sea are rich in feldspar. Compared with other areas, sediments in this region are rich in hornblende transported from volcanic and sedimentary rocks in Siberia by the Anadyr Stream and the Siberian Coastal Current. Sediments in the eastern Chukchi Sea are rich in quartz sourced from sediments of the Yukon and Kuskokwim rivers carried by the Alaska Coastal Current. Sediments in the northern Chukchi Sea are rich in quartz and carbonates from the Mackenzie River sediments. （2） Sediments of the southern and central Canada Basin contain little calcite and dolomite, mainly due to the small impact of the Beaufort Gyre carrying carbonates from the Canadian Arctic Islands. Compared with other areas, the mica content in the region is high, implying that the Laptev Sea is the main sediment source for the southern and central Canada Basin. In the other deep sea areas, calcite and dolomite levels are high caused by the input of large amounts of sediment carried by the Beaufort Gyre from the Canadian Arctic Islands （Banks and Victoria）. The Siberian Laptev Sea also provides small amounts of sediment for this region. Furthermore, the Atlantic mid-water contributes some fine-grained material to the entire deep western Arctic Ocean.  相似文献   

5.
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   

6.
Sediment cores with length of 25 - 45cm at 12 stations in Zhujiang(Pearl) River Estuary were sampled in summer of 1999. Chemical components (Al2O3 , Fe2O3, CaO, TiO2, Cu, Pb, Cr, Zn, Co, Ni, V, Ba, Sr and Y) and grain sizes were analyzed. Sediments in Zhujiang River Estuary are characterized by relatively coarse grain size. The grain sizes of the sediments in the area outside the estuary are relatively finer than those in the north part of the estuary but coarser than those in the middle of Lingdingyang and have a trend similar to the spatial distribution trend of some chemical components such as Fe2O3, Al2O3, TiO2, V, Cu, Ni, Zn and Y. This showed that grain size is an important factor that controls the spatial distribution and depth profile of chemical elements in the Zhujiang River Estuary. Frequent re-suspension, re-transportation and redistribution of settled sediment on estuary floor could be deduced from the spatial distributions and depth profiles of chemical components. Except for CaO and Sr, the chemical components always enrich at the west side of, in the middle of, and at the north side of, the estuary. Fe2O3, Al2O3, Ti, V, Cr, Ni, Zn, Cu and Y in Zhujiang River Estuary sediments mainly result from rock and soil weathering except that parts of Cr, Ni, Zn Cu and Y are anthropogenic. CaO and Sr in sediments originate from marine source. Although Co as well as Pb derives from anthropogenic sources, human activities related to Co might differ from the activities related to Pb.  相似文献   

7.
1INTRODUCTIONPolycyclicaromatichydrocarbons (PAHs)depo sit edinmarineenvironmentsfromavarietyofsourcessuchaswastewater,industrialanddomesticdischarges,andoilspills.Themajorityofthesesourcesfrompetrogenicoriginischaracterizedbyadominanceoflowmolecularweightaromaticcompounds,especiallynaphthaleneandalkylatedPAHs(Sportoletal.,1 983 ) .Crudeoilanditsrefinedproductssuchasgasoline,keroseneandotherfu eloilshaveahighcontentofalkylatedPAHsduetotheirslowformationattemperatureslowerthanthatofcomb…  相似文献   

8.
Ninety-eight clay mineral samples from the YSDP102 core were analyzed by x-ray diffractometer to study the four clay minerals: illite, chlorite, kaolinite and smectite. Twenty-eight samples had been analyzed on the laser particle-siz eanalyzer to reveal the particle features of the sediments. Distribution of the clay minerals and the particle characteristics in the YSDP102 core show that the core experienced three different depositional periods and formed three different sedimentary intervals due to different sediment sources and different depositional environments. Features of the clay minerals and the heavy minerals in the YSDP102 core indicate that coarse-grained sediments and fine-grained sediments result from different sources. The Yellow Sea Warm Current has greatly influenced the sedimentary framework of this region since the current‘s formation.  相似文献   

9.
Detrital minerals of 137 offshore and 22 river sediment samples collected from Qingdao coastal areas have been analyzed. Four mineral assemblage provinces can be classified by Q-mode cluster analysis. Factor analysis identifies two major factors that account for the total variability in most common minerals: 1) based on the relationship of quartz, hornblende, actinolite, micas, and authigenic pyrite, 41.55% of the variability is related to sediment sources; 2) based on the relationship of epidote, garnet, sphere, and ilmenite, 23.21% can be related to strong hydrodynamic conditions that control transport and sedimentation. By comparing mineral compositions of river waters in the study area, the following four mineral provenances can be identified. The Qingdao-Laoshan nearshore area has a quartz-feldspar-epidote-hornblende-limenite-limonite-sphene assemblage, which is largely attributed to relict sediment and coastal erosion. The Jimo-Haiyang nearshore area has a quartz-feldspar-hornblende-epidote-limonite-mica-actinolite assemblage, derived largely from the Wulong River and Rushan River, and is also affected by the Huanghe River, while the Qianliyan Island area in the deeper offshore area separated by a mud belt has a similar assemblage. The Haiyang-Rushan nearshore area has a quartz-feldspar-hornblende-epidote-micas-limonite assemblage, indicating multiple sources from the Rushan River, the Wulong River, the Huanghe River, and coastal erosion. The central area, located in an eddy center, has a mica-authigenic pyrite-hornblende-quartzfeldspar assemblage, indicating multiple sources dominated by Huanghe River distal sediments.  相似文献   

10.
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   

11.
The Jianggang Harbour-centered radial sand ridge (RSR) is the largest sand body in the Yellow Sea. Its formation and evolution are of interest for scientists of various fields; however, the sediment provenance is uncertain. In this study, rare earth element (REE) geochemical compositions of the RSR sediments together with their potential sources are investigated to identify the provenance of the RSR sediments. The typical parameters ((La/Yb)N, (La/Sm)N and (Gd/Yb)N) as well as the upper continental crust-normalized patterns of REEs can only be associated with source rocks, and thus can be used as effective tracers for the origin and sources of sediments. However, the REE contents of sediments are affected by many factors, such as particle sorting and chemical weathering. Onshore RSR sediments are different in REE geochemical composition from offshore RSR sediments to some extent, suggesting that not all of the offshore RSR sediments have the same sources as the onshore RSR sediments. Meanwhile, the sediments adjacent to the northeast of Cheju Island and at Lian Island near the Lianyun Harbour were not the source of the RSR sediments due to their distinctive REE patterns, δEu, (La/Yb)N, (Gd/Yb)N and (La/Sm)N. The Korean river sediments could be dispersed to the Jiangsu Coast slightly impacting the fine fractions of the RSR sediments, particularly the offshore RSR sediments. Additionally, geochemical comparisons show that the modern Yellow River was responsible for the onshore RSR sediments, whereas the sediment loads from the Yangtze River could serve as a major contributor to the RSR, particularly the offshore RSR. In addition, the offshore RSR could also be partly fed by an unknown source due to some high values of (La/Yb)N, (La/Sm)N and La contents differing from those of the Chinese and Korean river sediments.  相似文献   

12.
Sediment transport in estuarine systems has been of increasing interest for scientists during the past few decades. However, the mechanisms for sediment redistribution remain unclear. We characterized in detail sediment transport in the Xiaoqing River estuary using the mathematical Weibull function to partitiongrain-size components of surface sediments in the southwestern Laizhou Bay, Northeast China. Four partitioned components: finer than 4, 4.6–12.5, 23.4–63.3, and 67.1–132.6 μm were interpreted in terms of hydrodynamic conditions. During sediment transport, silt grains were suspended and moved seaward from three depositional centers, whereas fine-grained sands moved generally landward. Overall, sediments are transported clockwise in a generally NNE direction near shore and then turn eastward offshore. The mathematical partitioning method showed a great potential for future estuarine environmental studies.  相似文献   

13.
The growth of tidal fl ats off Zhejiang coasts in southwestern China has provided substantial areas for local agriculture and construction activities. To evaluate modern and future development of tidal fl ats in the region, a good understanding of sediment sources is necessary. Previous research has concluded that the Changjiang(Yangtze) River is the dominant supplier of sediments to this part of the southeast Chinese coast, despite the fact that sediment delivery from this source has been decreased markedly in the past two decades. In this study, we investigated the sources of tidal fl at sediments, and the magnetic and geochemical properties of recent tidal fl at sediments along the Zhejiang coast were compared with those discharged from rivers. Magnetic and geochemical properties of the tidal fl at samples reveal statistically distinct sediment provenance groups. The magnetic and geochemical scatter plots show that the suspended sediment samples are naturally divided into two diff erent groups, one including the Changjiang River and Qiantang River material, and the other including the Jiaojiang, Oujiang, and Feiyun Rivers that located in the central and southern parts of the study areas. At last, a binary source of tidal fl at sediments along the Zhejiang coast was determined, with the substantial majority originating from local rivers, while a much smaller proportion emanates from the Changjiang River to the north. We conclude that the sediment contribution of the Changjiang River to tidal fl at development in the region has been markedly overestimated, with important implications for management.  相似文献   

14.
Based on the measured data, suspended sediment concentration, surface sediment grain size, current and waves, the sediment transport mechanisms and pathways in the Phoenix Island area were analyzed using methods of flux decomposition and Grain Size Trend Analysis (GSTA). The results show that net suspended sediment is mainly transported by average current, Stokes drift, and gravitational circulation. The transport direction of suspended sediment is varying and basically following the direction of residual tidal currents. Surface sediment transport pathways are primarily parallel to the coastline along with two convergent centers. Waves and longshore currents have a significant influence on sediment transport, but the influence is limited due to a steep and deep underwater bank. Tidal current is the main controlling factor for sediment transport, especially in the deep water area. Neither suspended nor surface sediment is transported towards the southwest. The South Shandong Coastal Current (SSCC) has little effect on sediment transport processes in the nearshore area of Phoenix Island.  相似文献   

15.
The concept of water age is applied to calculate the timescales of the transport processes of freshwater in Lianzhou Bay,using a model based on ECOMSED.In this study,water age is defined as the time that has elapsed since the water parcel enters the Nanliu River.The results show that the mean age at a specified position and the runoff of the Nanliu River are well correlated and can be approximately expressed by a natural logarithmic function.During the neap tide,it takes 70,60 and 40 days in the dry,normal and rainy seasons for water to travel from the mouth of the Nanliu River to the northeast of Lianzhou Bay,respectively,which is not beneficial to water exchange in the bay.Tides significantly influence the model results;it takes five less days for the tracer to be transported from the mouth of the Nanliu River to the north of Guantouling during the spring tide than during the neap tide.  相似文献   

16.
Distribution of suspended matter in seawater in the Southern Yellow Sea is investigated in five regions: 1) the Northern Jiangsu bank, the highest TSM (total suspended matter) content region; 2) the high TSM content region off the Changjiang River mouth; 3) the high TSM content region off the Chengshan Cape; 4) the low TSM region off Haizhou Bay; 5) the central part of the Southern Yellow Sea, a low TSM content region. The vertical distribution of TSM is mainly characterized by a spring layer of suspended matter, written as “suspended-cline” whose genesis is related to storms in winter. In this paper, non-combustible components and grain sizes in suspended matter, relationship between suspended matter and bottom sediments, and salinity in seawater are described. Investigation result shows that, in this area, suspended matter comes mainly from resuspended bottom sediment and secondarily from present discharge loads from rivers and biogenic materials. Discharged sediments from the Huanghe River move around the Chengshan Cape and affect the northwestern region of this area. Sediments from the Changjiang River affect only the southern part and have little or no direct influence on the central deep region. Wave is the main factor affecting distribution of suspended matter. Water depth controls the critical depth acted on by waves. The cold water mass in the central region limits horizontal and vertical dispersions of terrigenous materials. Suspended matter here has the transitional properties of the epicontinental sea. Its concentration and composition are different from those of a semi-closed sea (such as the Bohai Sea) and those of the East China Sea outer continental shelf or those near oceanic areas.  相似文献   

17.
Light transmission data collected from June to July 1987 and from February to March 1997 by the R/V Kexue 1 in the East China Sea were used to analyze its distribution characteristics and its relation to the sediment transport in this sea. Some results obtained were: (1) The Taiwan Warm Current flowing northwards seemed to be a barrier preventing suspended matter discharged from the Changjiang River Estuary from continuously moving southeastward and causing the suspended matter to flow along a path near 123°30′E in summer and 123°00′E in winter. (2) Suspended matter in the area adjacent to the Changjiang River Estuary could not be transported southward along the coast in summer due to opposing offshore currents including the Taiwan Warm Current flowing northward and the Changjiang Diluted Water turning northeastward. (3) The thermocline and temperature front bar suspended matter from crossing through.  相似文献   

18.
We analyzed heavy metal concentrations in a number of surface sediments and cores from the Qiongzhou Strait and surrounding marine areas.The areas of high concentrations are primarily outside the eastern mouth of the Qiongzhou Strait and on the west side of the Leizhou Peninsula,whereas the areas of low concentrations are located primarily in the eastern Qiongzhou Strait.The maximum Cd,Pb and Zn concentrations in the samples collected in our study do not exceed the official standards for marine sediments,whereas the concentrations of Cr and Cu slightly exceed the standards.Correlations exist between the concentrations of Cu,Pb,Zn,Cr and Cd,and the concentrations of these metals are positively correlated with the mean particle size(φ value),indicating that the finer sediments have adsorbed greater amounts of heavy metal elements than the coarser sediments.An evaluation of the potential environmental risks demonstrates that certain indices of heavy metal pollution and environmental risks are relatively low and may be assigned low risk levels,thereby indicating that,in terms of heavy metals,the marine sedimentary environment in this region is only mildly impacted.Our analysis of the contaminant origins shows that the heavy metals in this region primarily originate in the Pearl River Estuary and that a small amount of them is derived from local runoff.The elevated heavy metal concentrations from the upper sections of the cores started 130 years ago,which indicats that heavy metals in the surface sediments are primarily due to human activities associated with industrialization.  相似文献   

19.
Relocation of the Yellow River estuary has significant impacts on not only terrestrial environment and human activities, but also sedimentary and ecological environments in coastal seas. The responses of regional geochemical characteristics to the relocation event, however, have not been well studied. In the present study, we performed detailed geochemical elemental analyses of a sediment core from the northern Yellow Sea and studied their geochemical responses to the 1855 AD relocation of the Yellow River estuary. The results show that TOC/TN, Co/Al2O3, Cr/Al2O3, Ni/Al2O3 and Se/Al2O3 ratios all decreased abruptly after 1855 AD, and similar decreases are observed in the sediments of the mud area southwest off the Cheju Island. These abrupt changes are very likely caused by the changes in source materials due to the relocation of the Yellow River estuary from the southern Yellow Sea to the Bohai Sea, which the corresponding decreasing trends caused by the changes in main source materials from those transported by the Liaohe River, the Haihe River and the Luanhe River to those by the Yellow River. Because the events have precise ages recorded in historical archives, these obvious changes in elemental geochemistry of sediments can be used to calibrate age models of related coastal sea sediments.  相似文献   

20.
To understand the provenance and evolution of eolian input in the last 1.95 Ma in the Parece Vela Basin in the eastern Philippine Sea, the clay mineral assemblage of a gravity core PV090510 from the basin was investigated using paleogeomagnetic dating and X-ray diffraction. The assemblage of the core mainly consisted of smectite （-46%） and illite （-40%）, with some chlorite （-10%） and kaolinite （-4%）. Analysis of the provenance of these minerals suggested that smectite was mainly derived from volcanic rocks of the Mariana Arc, while illite, chlorite, and kaolinite were mainly transported as eolian dust by the East Asian monsoon from central Asia. We used the ratio of （illite＋chlorite＋kaolinite）/smectite as a proxy for Asian eolian input to the Parece Vela Basin since 1.95 Ma. This ratio followed glacial and interglacial cycles and was consistent with the intensity of the East Asian monsoon and aridity of central Asia since 1.95 Ma. The changes of the ratio reflected three different stages of the East Asian monsoon and provenance climate.  相似文献   

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