Source Evolution and Its Relationship to Climate Change Since the Middle–Late Pleistocene in Laizhou Bay,China

Through the geochemical analysis of two hundred-meters cores KD4 and ZK3 from Laizhou Bay,in this study,we determined the distribution law and controlling factors of the geochemical elements.We analyzed 24 elements with respect to their R factors and major principal components,which were combined with the source discrimination functions DFCr/Th and DFCa/Al to obtain the sediment source index and its variation with depth for this area.A comparison of the changes in climate indicators suggests a clear correlation between the source and climate changes.The results show that the Yellow River and surrounding short-term rivers are the main sediment sources in this area.The PC3 of the KD4 core and PC2 of the ZK3 core(e.g.,CaO,MnO,SiO2)exhibit significant variations and reflect the relative contributions of Yellow River sources.The deposition process can be divided into six stages:in Phase I(MIS 5c–MIS 5a),the Yellow River formed,and the composition of the Yellow River had a greater influence on the sedimentary composition of the study area.In Phase II(MIS 5a–MIS 3),the sediment sources of the Yellow River and the short-term streams in this area were wavering,with the sediments derived from short-term rivers playing a more important role.In Phase III(MIS 3),with a sharp drop in temperature,the study area was in the process of retreat,and the sediment source changed from the Yellow River to short-term rivers,after which the Yellow River source material remained the main sediment source for the region.A similar process occurred three more times in Phase IV(MIS 3–MIS 2),Phase V(MIS 2–MIS 1),and Phase VI(MIS 1).With changes in climate,especially during alternating sea-land phases,the sediment source varied in marine-terrestrial-marine phases,and the changes are observed as Yellow River source-surrounding provenance-Yellow River source.However,this process of change is not synchronized with the sea-land strata alternation.     

MONITORING THE DIFFUSION OF SUSPENDED SEDIMENTS AND STABILITY OF TIDAL RADIAL SAND RIDGES AREA USING MULTI-SATELLITE REMOTE SENSING DATA

Nine Landsat TM tapes and images and MSS images, 10 NOAA tapes and images and 1 SAR image from 1973 to 1997 were used to analyse the diffusion of suspended sediments and the change of tidal radial sand ridges in the northern part of the Changjiang River delta, the South Yellow Sea. The results showed that the diffusion of suspended sediments was controlled by the tide, net current, and submarine topography in this area. The distribution of suspended sediments had close relationship with thesubmarine topography. The old Huanghe River delta and the Changjiang River comprise the main sediment supply for the formation of radial sand ridges, whose evolution can be divided into three stages since the Huangbe River changed its course and flowed northward into the Bohai Sea.     

Clay minerals and geochemistry of the bottom sediments in the northwestern East China Sea

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.     

Using geochemistry of rare earth elements to indicate sediment provenance of sand ridges in southwestern Yellow Sea

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.     

A contrast analysis on the load character of the Changjiang River and the Huanghe River

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A contrast analysis on the load character of the Changjiang River and the Huanghe River

According to the analysis of grain size, mineral composition and inclusion in quartz grain of the suspended and bed load sampled from the Changjiang (Yangtze) River and the Huanghe (Yellow) River, the authors reveal the differentiation of loads between the two rivers. In the Huanghe River the size of suspended load is coarser than that in the Changjiang River, while the bed load is on the contrary. Through heavy mineral analysis, the biotite content of the Huanghe River loads is much higher than that of the Changjiang River, and the monomorillonite content of the former is about two times higher than the latter. All those may be attributed to the effects of different material sources and hydraulic conditions on load. The analysis of inclusion in quartz grain definitely illustrates the environmental difference of material sources between the two rivers. In the meantime, it provides a new method in seeking source of river load. Subsidized by the National Natural Science Foundation. This paper is attributed to careful guidance from Prof. Wang Ying & Prof. Shi Yunliang.     

High resolution records of flood deposition in the mud area off the Changjiang River mouth during the past century

This paper presents a paleoflood study to determine the flood frequency of the Changjiang River, based on core cj0702, taken from the Changjiang River subaqueous delta. We identified flood deposits by means of high-resolution grain-size variation, sensitive population, geochemical indexes and magnetic susceptibility. The core covers a time span of 120 years by 210 Pb dating and was sampled at 1–2 cm intervals. Grain size, geochemical elements, and physical parameters were analyzed. The results indicate that the sediment of the core is mainly composed of silt and clay, as well as groups of interbedded silt, clay silt, and clay. Vertically, the grain size pattern was controlled by seasonal variations in water discharge and by the sediment input in winter from the abandoned Huanghe River delta. River flooding caused extreme values in all our measured parameters. We identified more than 20 flood events that occurred since 1887 using the physical parameter analysis method. The environmentally sensitive component of sediment grain size(14.32–96.39 μm) contribution30%, Zr/Rb ratio1.5, and magnetic susceptibility16 were selected as the criteria for flood identification generally. We also found that floods that had taken place in the upstream, midstream, or downstream parts of the river were clearly identified by these indexes while the large-scale floods that covered the whole drainage area did not leave clear indications in the sediment record. This study for identification of flood events is of great significance for understanding hyperpycnal current sedimentation as well as for forecasting of floods.     

Sedimentary facies of the subaqueous Changjiang River delta since the late Pleistocene

The sedimentary facies of the subaqueous Changjiang(Yangtze) River delta since the late Pleistocene was studied based on lithology and foraminifera analysis for two boreholes,CJK07 and CJK11,along with14C dating.Four sedimentary facies were identified,namely fluvial,tidal flat,offshore,and prodelta facies.The fluvial sedimentary facies is comprised of fluvial channel lag deposits,fluvial point bar deposits,and floodplain deposits,showing a fining-upward sequence in general with no benthic foraminifera.A layer of stiff clay overlies the fluvial deposits in core CJK07,indicating a long-term exposure environment during the Last Glacial Maximum(LGM).During the postglacial sea-level rise around 13-7.5 cal ka BP,the tidal flat facies was deposited in core CJK11,characterized by abundant silt-clay couplets.Euryhaline species dominate the subtidal flat foraminiferal assemblages,while almost no foraminifera was found in the intertidal flat.The offshore environment was the major sedimentary environment when the sea level reached its highest level around 7.5 cal ka BP,with a maximum accumulation rate of 10 mm/a found in core CJK11.Prodelta sediments have been deposited in core CJK11 since ~3 cal ka BP,after the formation of the Changjiang River delta.The difference in sedimentary facies between core CJK07 and CJK11 is due to their location: core CJK07 was in an interfluve while core CJK11 was in an incised valley during the LGM.Furthermore,AMS14C dating of core CJK07 shows poor chronological order,indicating that the sediments were reworked by strong tidal currents and that sediment deposited since ~7.7 cal ka BP in core CJK07 was eroded away by modern hydrodynamic forces caused by the southward shift of the Changjiang River delta depocenter.     

Characteristics of Heavy Minerals and Quantitative Provenance Identification of Sediments from the Muddy Area Outside the Oujiang Estuary Since 5.8 kyr

The heavy mineral compositions of the sediments in core D04 with a length of 20.2 m from the muddy area outside the Oujiang Estuary along the coast of Zhejiang-Fujian Provinces have been analyzed. Core D04 can be divided into three units: DU1(0–7.4 m), DU2(7.4–11.4 m) and DU3(11.4–20.2 m). The results showed that the heavy minerals are authigenic pyrite(65.6%)– hornblende(16.0%) – epidote(4.6%) assemblages. The core sediments are mainly composed of clayey silt, which belongs to the clinoform deposit formed since 5.8 kyr, indicating a weak hydrodynamic environment. The deposition rates changed in the trend of high-low-high upward. Quantitative analysis shows that the core sediments were mainly from the suspended sediments of the Changjiang(Yangtze) River, accounting for 79.2%, with only 10.0% from Oujiang, and 10.8% from other provenance. The Oujiang-derived sediments were gradually increased from the bottom unit DU3(3.1%) to the top unit DU1(17.8%), but the Changjiang-derived sediments were gradually decreased. The source changes are closely related to the development of Yangtze River Delta and Wenzhou Bay, climate changes and human activities. During the period of 2.1–3.7 kyr, the sediment supply was greatly reduced due to the poor reclamation capacity of the river basins, resulting in a low deposition rate. Since 2 kyr, the enhancement of human activities in the Yangtze River Basin and the Oujiang River Basin led to more soils to be eroded and transported to the study area. Due to the short distance of the site of core D04 from the Oujiang River mouth, the study area received more Oujiang-derived sediments when upper unit(DU1) deposited than the lower units(DU2 and DU3).     

Mineralogical study of surface sediments in the western Arctic Ocean and their implications for material sources

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.     

Characteristics of Light Transmission in Summer and Winter and Its Relation on Sediment Transport in the East China Sea

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.     

Seasonal variation of tidal prism and energy in the Changjiang River estuary:a numerical study

Tidal rivers are intrinsically complex because tidal propagation is influenced by river discharge. This study aims to examine the seasonal variation of tidal prism and energy variance in the tidal river of the Changjiang(Yangtze) River estuary in China. In order to quantify the behaviour of river and tide,we use numerical modelling that has been validated using measured data. We conduct our analysis by quantifying the discharge and energy variance in separate components for both the river and the tide,during wet and dry seasons. We note various definitions of tidal prism and explore the difference between tidal discharge on the flood and ebb and tidal storage volume. The results show that the river discharge attenuates the tidal motion and reduces the tidal flood discharge but the tidal storage volume is approximately constant with different riverine discharge since part of the fresh water discharge is intercepted and captured in the estuary due to the backwater effect. It appears that the tidal discharge adjusts according to the variation of river discharge to keep a constant tidal storage volume. An analysis of the hydraulics shows that the transition from tidal dominance(at the mouth) to river dominance(upstream) depends on the location of tidal current reversal which varies from wet season to dry season. Duringthe wet season,the Changjiang River estuary is totally dominated by energy from fresh water discharge.     

Relocation of the Yellow River estuary in 1855 AD recorded in the sediment core from the northern Yellow Sea

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.     

MIXING OF SALT WATER AND FRESH WATER IN THE CHANGJIANG RIVER ESTUARY AND ITS EFFECTS ON SUSPENDED SEDIMENT

Using field hydrological data, the relationship between the mixing of salt water and fresh water and the tidal range/ high tidal level in the Changjiang (Yangtze) River estuary is discussed, and the transporting and concentrating of suspended sediment in the estuary were also analysed in respect to the circulation, flocculation and stratified interface resulting from mixing.The calculation results by two-dimentional box model have confirmed the effects of the circulation on the concentrating of suspended sediment in the estuary. The conclusions derived from this work have deepened the understanding on the mixing in the Changjiang River estuary and are of significance in bo'th theory and practice.     

Influences of hydrological regime on heavy metal and saltion concentrations in intertidal sediment from Chongming Dongtan,Changjiang River estuary,China

The tidal flat along the Changjiang(Yangtze) River estuary has long been reclaimed for the agricultural purposes, with the prevailing hydrological conditions during such pedogenic transformations being of great importance to their successful development. In this study, samples of surface sediment from Chongming Dongtan, situated at the mouth of the Changjiang River estuary, were collected and analyzed in order to understand how hydrological management can influence the concentrations of heavy metals and salt ions in pore water, and chemical fractionation of heavy metals during the reclamation process. We performed a series of experiments that simulated three dif ferent hydrological regimes: permanent flooding(R1), alternative five-day periods of wetting and drying(R2), continuous field capacity(R3). Our results exhibited good Pearson correlations coefficients between heavy metals and salt ions in the pore water for both R1 and R2. In particular, the concentrations of salt ions in the pore water decreased in all three regimes, but showed the biggest decline in R2. With this R2 experiment, the periodic concentration patterns in the pore water varied for Fe and Mn, but not for Cr, Cu, Pb and Zn. Neither the fractionation of Ni nor the residual fractions of any metals changed significantly in any regime. In R1, the reducible fractions of heavy metals(Cr, Cu, Zn and Pb) in the sediment decreased, while the acid extractable fractions increased. In R2, the acid extractable and the reducible fractions of Cr, Cu, Zn and Pb both decreased, as did the oxidizable fraction of Cu. These data suggest that an alternating hydrological regime can reduce both salinity and the availability of heavy metals in sediments.     

日照市海岸带海滩沉积物粒度特征及物源分析

根据日照市海岸带2个重点海滩所采集的样品,通过粒度、磁化率、主微量及稀土元素等方面的调查资料,综合分析了研究区沉积物类型、分布特征、搬运路径及物质来源。结果表明,研究区沉积物类型以砂为主,在平行海岸方向上,沉积物粒径自北至南由细变粗。在垂直海岸方向上,从滩肩到滩面再到低潮线处,沉积物粒径逐渐变细。海滨国家森林公园海滩的分选性要好于万平口海水浴场海滩。沉积物受黄海沿岸流影响,多自北向南运移。海滩中浅部物质的来源与陆内一侧基岩中斜长片麻岩和二长花岗岩的关系较为密切,深部物质的来源与靠海一侧基岩中花岗斑岩和花岗闪长岩的关系较为密切。     

Distribution and Sources of Polycyclic Aromatic Hydrocarbon （PAH） in Marine Environment of China

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

Study on suspended matter in seawater in the Southern Yellow Sea

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.     

Geochemical studies of U,Th, Ra,40K in seciments of the China Sea and adjacent sea area,and lower reaches of several Chinese Rivers

Geochemical studies of the U, Th, Ra, and⁴⁰K in surface sediments of the China Sea and adjacent sea areas, the lower reaches of the Huanghe and Changjiang Rivers and the estuaries of the Zhujiang and Rongjiang Rivers were carried out with a model 8180-4K multichannel Ge(Li)γ spectrometer in 1981–1985. The mean values of U, Ra, Th,⁴⁰K are about 2.11 ppm, 7.67×10⁻¹³g/g, 11.00 ppm, and 2.33 ppm respectively, in the China Sea, the Okinawa Trough, and the Changjiang and Huanghe River estuaries. The distribution of the four isotopes is uniform in the above zone. The contents of U and Th in the sediments of the Zhujiang and Rongjiang Rivers and the Fujian coast are 1–4 times higher than those of the above zone and are related to the granite and radioactive ore present in the upper reaches of these rivers or the adjacent mountains. The distributions of U, Th, Ra, and⁴⁰K are related to the physico-chemical property, redox state, geological type and grain size of the sediment, and biotic activity. Contribution No. 1408, Institute of Oceanology, Academia Sinica, Qingdao.     

黄河三角洲海岸线遥感动态监测

黄河三角洲是世界上海岸线变迁最快的地区之一。遥感与GIS技术相结合,能准确及时地监测黄河三角洲海岸线的动态演变。本文以1976年以来多时相遥感影像为主要数据源,通过几何精校正与配准,形成统一投影与坐标体系的遥感影像,运用平均高潮线法,对20景时间序列影像经分类处理后提取海岸线;另经GIS叠加分析,剖析了现行黄河河口、钓口河口地区海岸线的演变过程及其规律。