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1.
Sediment grain size effect on benthic microalgal biomass in shallow aquatic ecosystems 总被引：1，自引：0，他引：1
Benthic microalgal biomass is an important fraction of the primary producer community in shallow water ecosystems, and the factors controlling benthic microalgal biomass are complex. One possible controlling factor is sediment grain-size distribution. Benthic microalgal biomass was sampled in sediments collected from two sets of North Carolina estuaries Massachusetts and Cape Cod bays, and Manukau Harbour in New Zealand. Comparisons of benthic microalgal biomass and sediment grain-size distributions in these coastal and estuarine ecosystems frequently showed a negative relationship between the proportion of fine-grained sediments and benthic microalgal biomass measured as chlorophylla. The highest sedimentary chlorophylla levels generally occurred in sediments with lower percentages of fine particles (diameter <125 mm). A negative relationship between the proportion of fine sediments and benthic microalgal biomass suggests anthropogenic loadings of fine sediment may reduce the biological productivity of shallow-water ecosystems. 相似文献
2.
In estuaries, organic coatings play an important role in the aggregation of mineral particles. Particles acquire adhesive surfaces through the activities of bacteria and microalgae in the sediment and water column. Eventually, they may become incorporated into larger aggregates and structures, such as tubes, constructed by infaunal benthic animals. Where these structures are large enough, and the adhesive bonds between particles strong enough, individual particles may remain in place at bed shear stresses otherwise strong enough to cause sediment transport. This study examined the aggregation of particles during tube building by the ubiquitous tanaid crustaceanLeptochelia dubia. Particle size selection and rates of tube building were determined as functions of animal size, temperature, and the presence or absence of bacteria and microalgae. These data were used to model seasonal patterns of sediment binding by a population ofL. dubia in Yaquina Bay, Oregon, taking into account seasonal changes in sizes and abundance of animals. Rates of tube building (mass of sediment per day) increased with animal size, but temperature had no effect. The model indicated that the field population ofL. dubia bound sediment into tubes at a gross rate of 350 g m?2 d?1, averaged over a 2-yr period. Seasonally, gross rates of tube building were predicted to range from 70 g m?2 d?1 (during late winter-early spring) to 600 g m?2 d?1 (during autumn). When constructing tubes from sterile sediments, small animals selected silt-sized particles while large animals discriminated against these particles. The presence of microbes in sediments tended to reduce particle selectivity. 相似文献
3.
The prerequisite for obtaining variations of terrigenous grain-size of marine sediments is how to effectively remove non-terrigenous matters and preserve terrigenous particles synchronously. Combined with observations under biological microscope and scanning electron microscope, a comparative study of biogenic debris removal effect and terrigenous grain-size analysis under different pretreatment condition was performed on core sediments, which were retrieved in the South China Sea during the MD190 cruise. Our new results showed that the main three biogenic particles, namely, organic matter, carbonate, and opal in marine sediments could be removed effectively by 30% H2O2 in a stirring water bath at 60 ℃ for 3 h, 0.5% HCl for 1 h, and 2 mol/L Na2CO3 in a stirring water bath at 85 ℃ for 5 h, in turn. Such pretreatments achieved the goals of biogenic debris removal efficiency and relatively well-preserved terrigenous particles. Prior to selecting an appropriate pretreatment method, this study suggested that the actual effects of biogenic detritus on grain-size results of diverse marine sediment samples should be taken into account. If the laboratory data are ensured to be closer to the natural grain-size distribution of terrigenous particles, the removals of all biogenic debris are not always needed, and the less pretreatment processes the better. For example, opal particles have little effect on terrigenous grain-size distribution when their percentage is lower than 2%. Thus, there is no use to remove them from marine sediments before laboratory grain-size analysis of terrigenous particles. Additionally, ultrasonic is not suggested through the whole process of terrigenous grain-size analysis because the strong energy of ultrasonic can lead to the fragmentation of some fragile terrigenous particles. 相似文献
4.
Survival of the tubicolous amphipodAmpelisca abdita in a sediment toxicity test was negatively correlated with the presence of indigenousNephtys incisa. The gut contents ofN. incisa held in uncontaminated sediment included identifiable portions of the amphipods.A. abdita andMicrodeutopus gryllotalpa. Although most nephtyid polychaete worms are active predators,Nephtys incisa has been considered a nonselective deposit-feeder. We coclude thatN. incisa will prey upon amphipods under laboratory conditions. This predation may be a factor in the exclusion of surface-dwelling amphipods from theNephtys-Nucula community common in southern New England. 相似文献
5.
Marsh creation has come into increasing use as a measure to mitigate loss of valuable wetlands. However, few programs have addressed the functional ecological equivalence of man-made marshes and their natural counterparts. This study addresses structural and functional interactions in a man-made and two natural marshes. This was done by integrating substrate characteristics and marsh utilization by organisms of two trophic levels. Sediment properties, infaunal community composition, andFundulus heteroclitus marsh utilization were compared for a man-madeSpartina salt marsh (between ages 1 to 3 yr) in Dills Creek, North Carolina, and adjacent natural marshes to the east and west. East natural marsh and planted marsh sediment grain-size distributions were more similar to each other than to the west natural marsh due to shared drainage systems, but sediment organic content of the planted marsh was much lower than in either natural marsh. This difference was reflected in macrofaunal composition. Natural marsh sediments were inhabited primarily by subsurface, deposit-feeding oligochaetes whereas planted marsh sediments were dominated by the tube-building, surface-deposit feeding polychaetesStreblospio benedicti andManayunkia aestuarina. Infaunal differences were mirrored inFundulus diets. Natural marsh diets contained more detritus and insects, because oligochaetes, though abundant, were relatively inaccessible. Polychaetes and algae were major constituents of the planted marshFundulus diet. Though naturalmarsh fish may acquire a potentially less nutritive, detritus-based diet relative to the higher animal protein diet of the planted marsh fish,Fundulus abundances were markedly lower in the planted marsh than in the natural marshes, indicating fewer fish were being supported. LowerSpartina stem densities in the planted marsh may have provided inadequate protection from predation or insufficient spawning sites for the fundulids. After three years, the planted marsh remained functionally distinct from the adjacent natural marshes. Mitigation success at Dills Creek could have been improved by increasing tidal flushing, thereby enhancing, access to marine organisms and by mulching withSpartina wrack to increase sediment organic-matter content and porosity. Results from this study indicate that salt marshes should not be treated as a replaceable resource in the short term. The extreme spatial and temporal variability inherent to salt marshes make it virtually impossible to exactly replace a marsh by planting one on another site. 相似文献
6.
Sediments, sediment trap material, dominant surface plankton and collected fecal material were sampled concurrently with surface seawater in a coastal Mediterranean ecosystem and analyzed for non-volatile hydrocarbons and chlorinated hydrocarbons. Results showed consistent partitioning of hydrocarbon classes between dissolved and particulate phases of surface waters which appeared to be related to component solubility and particle availability. Analysis of biological materials showed the biota were important not only in packaging residues into large, fast sinking particles, but also in modifying the composition of components through metabolism and selective incorporation into body tissues and feces. Apparent sedimentation rate was calculated by analysis of 210Pb in sediment core samples and used to estimate average deposition rates of organics to the sea/sediment interface. The flux of particles through 100 m, as measured in the trap material in this sampling interval, was sufficient to balance most of the petroleum input to the sediments but accounted for only 17% of the average flux of PCBs to the sediments, and virtually none of the more soluble chlorinated hydrocarbon flux. Vertical transport via large fecal material compared to average background particles was seasonally low corresponding to a seasonal minimum in plankton biomass in late summer. Results show that hydrocarbon residues transported long distances away from input sources are highly modified, pointing to the geochemical significance of physical-chemical partitioning between seawater phases, incorporation into organisms and fecal material and biological/chemical degradation. 相似文献
7.
The grain-size statistics and environmental conditions of deposition of the beach and dune sediments from the Calangute region, Goa, have been studied. The results of Student's t test and bivariate plots reveal that there exist distinct differences in grain-size parameters of the sediments from different environments and that these differences are highly significant. The study shows that the variations in mean grain size (Mz), graphic standard deviation (O1), graphic skewness (Sk1), simple sorting measure (Sos) and simple skewness measure (Os) are significant in identifying the sediments from different environments. Further, the study reveals the usefulness of grain-size parameters not only in differentiating beach and dune sediments, but also in delineating the beach into foreshore and backshore. The differences in grain-size characteristics of the sediments between the environments reflect the transport, erosional and depositional mechanisms (active hydrodynamic processes in the beach foreshore and aerodynamic processes in the backshore and dune environments) prevailing in the area of study. 相似文献
8.
地表松散沉积物中不同粒级的颗粒蕴含着不同的信息,这种差异与其物质来源、搬运和沉积过程中的分选作用以及沉积后的风化作用等有关。因此,可根据沉积物中不同粒级颗粒地球化学特征与矿物组成的差异,进行沉积物物源追踪或沉积环境重建。选择青藏高原在气候和地貌方面具有典型意义的柴达木盆地、错那湖、雅鲁藏布江流域作为研究区,分别采集了这几个地区的沙丘沙、黄土、湖积物、冲积物、洪积物、残坡积物等地表松散沉积物样品,用干筛法将沉积物样品分为两个部分,粗颗粒部分粒径范围为≥75~500 μm,细颗粒部分粒径<75 μm。对上述粗、细颗粒分别进行稀土与微量元素、Sr-Nd同位素、轻矿物组成的实验室分析测试,并对沉积物中粗、细颗粒的测试结果采用古典多维尺度方法进行相似性分析。结果表明：青藏高原松散沉积物中粗、细颗粒在轻矿物组成、微量和稀土元素含量、稀土特征、元素参数等方面存在差异;细颗粒部分蕴含了更多的环境信息,富含容易受化学风化影响的黏土矿物以及硬度较小、容易被磨蚀的方解石等矿物。在物源示踪中不同气候区的沉积物细颗粒不宜进行直接比较,应根据样品的粒度分布情况优先选择合适的粗颗粒组分进行物源示踪。 相似文献
9.
小浪底水库运行后, 坝下游分组悬沙输移特点发生改变, 不同河段冲淤过程有所差别。基于1999—2018年坝下游实测水沙资料及固定淤积断面地形数据, 分析汛期分组悬沙输移的沿程调整特点, 建立分组悬沙输移及河床边界条件双重影响下不同河段河床累计冲淤量的计算关系。分析结果表明: ①汛期各组沙输沙率远小于蓄水前, 且中沙输沙率降幅最大, 在各水文断面平均降幅为85%;沿程上细沙输沙率基本不恢复, 而中沙和粗沙恢复距离分别到利津及艾山。②坝下游河床持续冲刷, 各河段河床组成均发生不同程度的粗化; 在拦沙后期(2007—2018年), 游荡段和过渡段床沙中细沙和中沙占比不足5%, 对悬沙几乎无补给作用, 而弯曲段床沙对中沙仍有一定的补给能力。③下游各河段以冲刷下切为主, 但调整幅度不同, 故对水流的约束能力有所差异。建立了各河段累计冲淤量与前期河相系数及进口断面分组来沙系数的经验关系, 并采用2019年下游水沙数据对公式进行了初步验证, 公式能合理反映断面形态与分组悬沙输移对河床累计冲淤过程的影响。 相似文献
10.
The Farasan Islands are located about 40 km offshore of Jizan area, southern Red Sea, Saudi Arabia. This is a preliminary study aiming to collect shoreline sediments from 17 stations to describe their main lithologic characters and identify the dominant molluscs that could help to evaluate the environmental conditions of these islands. Also, a sediment core FARA2 was collected from the intertidal area of Khor As Sailah Lagoon to see the development of shoreline sediments in this area with time. The results indicated that the shoreline sediments of the Farasan Islands comprised mainly of white, biogenic sand enriched in remains of corals, molluscs, calcareous algae, and benthic foraminifera. Thirty-four mollusc species were recorded from these sediments. Among them, Strombus fasciatus, Strombus tricornis, Chicoreus ramosus, Chicoreus virgineus, Tridacna maxima, and Tridacna squamosa were the most common molluscan in/near the shoreline sediments of Farasan Islands. Frequency abundances of sediment grain-size fractions in the core FARA2 indicated that the shoreline of the Khor As Sailah Lagoon is developing towards shallow intertidal setting due to high production of biogenic sediments by reefal communities. Metal concentrations (Fe, Mn, Cu, and Zn) in the sediment of the core FARA2 were stable throughout, showing no remarkable changes. This finding could indicate that flux of detrital components by fresh water runoff or wind-blown dust over the Farasan Islands was un-detectable during the deposition of these sediments. 相似文献
11.
稳定湖相沉积物和风成黄土粒度判别函数的建立及其意义 总被引：10，自引：2，他引：8
沉积物粒度变化主要受搬运介质、搬运方式、沉积环境和气候等多种因素的控制,通过粒度分析可判别沉积物的成因类型,推断其形成的沉积环境,解释环境演变。利用统计学方法对典型稳定湖相沉积物（罗布泊湖相样品２８２块,岱海湖相样品１２３块）和典型风成黄土（甘肃兰州榆中样品２６３块）粒度参数进行定量化分析,并经稳定湖相和风成沉积物验证,获得稳定湖相与风成沉积物的判别公式:Ｆ（湖相、风成沉积物） ＝２０．３６３Ｍｚ－５６．３７１Ｓｄ－６７．９２２Ｓｋ＋２３．５１６Ｋｇ－５５．６２６,若Ｆ＞０,为稳定湖相沉积物,反之,Ｆ＜０,则为风成沉积物。这为研究地史中稳定湖泊与风成环境 沉积物的鉴别提供粒度分析定量化判别方法,它对陆相古环境、干旱化事件和尘暴事件等研究具有十分重要的借鉴价值。 相似文献
12.
沉积物的形成受到多种地质因素的综合控制。通过粒度分析可判别沉积物的成因类型,推断其形成的沉积环境,解释环境演变;而沉积物的粒度组分除了受到原岩的控制外,还受到机械沉积作用的影响难以准确预测。运用人工神经网络对稳定湖相沉积物和风沉积物的粒度参数进行研究,将沉积物的4个粒度参数作为网络模型的输入变量,在对168个浙闽沿海迎风岸风成老红砂样品和282个苏贝淖湖滨湖泊沉积物样品所对应的粒度参数进行数据样本训练之后,获得了基于BP神经网络的稳定湖相和风沉积物预测模型。然后利用448个大树摆鱼湖相沉积物粒度参数样本和100个兰州榆中黄土风沉积物粒度参数样本作为测试样本对该模型进行了测试和验证,结果显示模型的可靠性较好,能够对沉积物的形成环境做出正确的判断。 相似文献
13.
Peter H Santschi Yuan-Hui Li Dennis M Adler Michael Amdurer Joy Bell Urs P Nyffeler 《Geochimica et cosmochimica acta》1983,47(2):201-210
The relative mobility of nuclides of Pb, Th, Pu, and Cs, which are widely used as geochemical tracers for sedimentation and bioturbation. was investigated in artificial microcosm tanks (MERL) and in Narragansett Bay. Their mobility was characterized by their removal rates from the water column, their affinity toward particles and their degree of penetration into the surface sediments. Pb, Th, and Pu transport was controlled predominantly by the affinity of these elements to particles, and the transport parameters of the particles themselves (i.e. sediment resuspension and mixing rates). Because of its low distribution coefficient, transport of Cs was controlled by molecular diffusion through pore water in the winter, while in summer, Cs transport was enhanced due to bioturbation. The increase with depth of the ratio in core profiles of MERL and Narragansett Bay sediments is thus caused primarily by the higher mobility of Cs. 相似文献
14.
Deriving transport pathways in a sediment trend analysis (STA) 总被引：1，自引：0，他引：1
Sediment trend analysis (STA) is a technique that enables patterns of net sediment transport to be determined by relative changes in grain-size distributions of all naturally occurring sediments. In addition, STA can determine the dynamic behaviour of bottom sediments with respect to erosion, accretion or dynamic equilibrium. The data requirements for STA are the full grain-size distributions taken from sediment grab samples collected at a regular spacing over a particular area of interest. Two types of methods are presently used in the derivation of the transport pathways: a line-by-line approach, in which transport pathways are determined by searching for sample sequences in which the distributions change, in a statistically acceptable manner; and various vector approaches, in which each sample is compared to neighbouring sites from which a vector sum is calculated.The basic assumption for STA is that the processes that cause sediment transport will affect the statistics of sediment distributions in a predictable way. In reality, this type of analysis is complicated through the inclusion of a number of uncertainties, or noise. The goal of STA is to extract the information (the transport pathways) from the noisy signal (the grain-size distributions), an approach that is made difficult because neither the nature of the information nor the noise is known. Because of this, obtaining results by simply applying its theory in a “black-box” approach may provide poor solutions.The line-by-line approach to STA draws from communications theory to achieve a solution. In some communications systems, the information from many sources is combined into one signal. The resulting signal is, from a statistical viewpoint, nothing but noise. The extraction of specific information assumes that information is indeed present, and determines if that assumption is consistent with the received signal. For STA, the procedure is to assume a transport direction over an area comprising many sample sites. From this assumption, the predicted sediment trends are compared with the pathways determined by the actual samples. The assumed transport direction is repeatedly modified until the best fit is achieved.Vector techniques may be very helpful to provide insights and guidance to the line-by-line approach. However, the approach is ultimately necessary to finalize a credible solution as well as providing important further information on the dynamic behaviour of the sediments, and to delineate specific sediment transport environments. 相似文献
15.
Geochemical characteristics of fine and coarse fractions of sediments in the Yarlung Zangbo River Basin (southern Tibet,China) 总被引：1，自引：0，他引：1
Shisong Du Yongqiu Wu Lihua Tan Wenmin Huang Chengzhi Hao 《Environmental Earth Sciences》2018,77(9):337
Tracing sources of aeolian sediment is key to reconstructing earth surface processes in arid areas and interpreting the paleoenvironmental significance of aeolian sequences. However, the difference of geochemical characteristics between different fractions of sediments in the Yarlung Zangbo River Basin (YZRB) is still unclear, so we want to identify which fraction of sediments is more suitable for tracing sediment sources. Considering the long distance between different wide valleys in the YZRB, we wonder whether there is any difference between these wide valleys in terms of geochemical characteristics of sediments. Forty-three surface sediment samples in the YZRB are collected, and the grain-size distributions and the major-element composition for 37 samples and the trace and rare earth element composition for the coarse (75–500 μm) and fine (<?75 μm) fractions of all samples are determined. The results reveal the following: (1) the fine fractions of the deposits contain more environmental information, suggesting that the fine fractions cannot be directly compared between different climate zones for provenance identification and that appropriate coarse fractions, based on the grain-size distribution of the targeted sediments, are more ideal for tracing sediment sources; and (2) geochemical characteristics of various sediment types show spatial heterogeneity. The coarse and fine fractions of the loose sediment samples can be divided into two regional groups based on geochemical characteristics: the Maquanhe zone in the upper reach, the Xigaze, Shannan and Mainling zone in the middle reach, which is consistent with the geological background of the YZRB; (3) aeolian deposits in the YZRB are a local origin and predominantly derived from the adjacent loose sediments, and fluvial sediments in the upper reach contribute little to the aeolian sands in the middle reach. 相似文献
16.
The goal of this work was to infer the spatio-temporal patterns of bottom circulation of San José Gulf (SJG), Patagonia, Argentina. The SJG is mainly affected by tidal circulation and presents two hydrographic domains. The Western Hydrographic Domain (WHD) presents vertically mixed waters year-round contrary to the seasonal stratified Eastern Hydrographic Domain (EHD), resulting in the formation of a thermal front between domains. Samples of sediments were collected in spring 2016 and summer 2017 at several locations to analyze the grain-size composition by means of laser diffractometry. A conceptual model of bottom hydrodynamics was inferred based on sediment's grain-size trends. Asymmetric dominant tidal currents affect bottom sediment distribution. A general northward sediment transport is dominant at the WHD, while at the EHD there is a seasonal shift in the transport direction. There, a net northward transport with a counterclockwise gyre dominates bottom hydrodynamics at the end of the thermal front formation, conditioned by residual currents. In contrast, a net southward circulation likely driven by strong westerly winds throughout autumn and winter prevails at the beginning of the water column stratification. The inferred sediment transport suggests a net loss of material that has to be recovered by tidal currents entering through the mouth and coastal sources as runoff, mudslides, and/or aeolian dust. 相似文献
17.
根据2016年伶仃洋128个表层沉积物粒度参数以及前人对伶仃洋表层沉积物的研究成果,结合Flemming沉积动力判别图解和粒径趋势分析模型（GSTA）,分析伶仃洋40年来的沉积格局演变特征,并探讨了人类活动在伶仃洋沉积格局演变中的作用。结果显示:1）2016年,伶仃洋表层沉积物中粉砂组分含量最多（56.67%）,黏土组分含量其次（26.08%）,砂含量最少（17.23%）,湾内表层沉积物总体较细,主要有砂、砂—粉砂—黏土、砂质粉砂、粉砂质砂和黏土质粉砂5种类型,各类型沉积物呈现斑块状分布。2）近40年来,伶仃洋表层沉积物的平均粒径、粒级组分的空间格局发生了显著变化,从之前的条带状分布变为斑块状分布,但沉积格局的剧烈演变主要集中于2004—2016年这十多年间,Flemming三角图分区变化显示出40年来伶仃洋沉积环境整体表现出动力增强的趋势。3）受人类大规模采砂影响,中滩区域原有的完整沉积中心被分散,分别向北和向南形成“两格局、三中心”的新型沉积模式,从而改变伶仃洋的沉积物源—汇过程。4）伶仃洋沉积物空间分布、沉积动力环境、运移趋势等特征的变化与采砂、航道浚深等人类活动有着密切的联系,反映出人类工程活动已成为影响伶仃洋沉积格局演变的重要因素。 相似文献
18.
《Applied Geochemistry》1999,14(6):807-816
A rapid procedure is described to evaluate the significance of inorganic and organic pollutants in fine-grained sediments. The air- (<30°C) or freeze-dried samples are screened within 30 min. in stainless steel sieves (<0.04 mm) prior to chemical analysis. This procedure is also suitable for analysis of such elements as Hg and many non-volatile organic pollutants. The sediment size fraction of <0.04 mm was chosen in order to separate the smallest grain-size obtainable by rapid dry-screening techniques; this is representative of the grain-size of suspended matter transported at low and medium river discharge (0.1–0.7 m/s). The screened fraction (<0.04 mm) of aquatic sediments is more homogeneous in grain-size and distribution, and the fine particles are more capable of adsorbing pollutants than coarser fractions. However, large differences are observed in grain-size distribution and adsorbable phases from one sample to another, even in the smallest size fractions (<0.04, <0.02, <0.002 mm). Clay minerals, Fe- and Mn-(oxy)hydrates, amorphous silica and humic substances all adsorb water at normal humidity. In order to estimate and standardise the adsorption capacity of the surface of these screened sediment fractions, the weight loss after heating at 105°C is used, instead of tedious quantification of all the above mentioned sediment phases. In addition, this procedure allows the rejection of sediment samples, unsuitable for monitoring purposes, which have very low adsorption capacities. In order to correct for the variable adsorption capacity of different sediment samples or size fractions, the weight loss (WL) at 105°C can be inserted in the widely used GeoIndex formula (Igeo105°=log2 (Cmeasured/Cbackground1WL105°C). This improves the evaluation of pollution in aquatic environments. 相似文献
19.
Zofia Noe Jennifer Jackson John J. Hutchens Jr. Keith Walters James O. Luken Kevin S. Godwin 《Estuaries and Coasts》2014,37(1):56-66
Increased freshwater and nutrient runoff associated with coastal development is implicated in dramatically altering estuarine communities along eastern US shorelines. We examined effects of three categories of shoreline development on high-marsh environments within Murrells Inlet, South Carolina, USA by measuring sediment nutrients, porewater salinity, plant species diversity, and above- and belowground plant biomass. Effects on new plant growth also were examined in plot clearing and transplantation experiments. Greater nutrient availability in sediments along developed shorelines was reflected in greater aboveground biomass and nitrogen storage in Juncus roemerianus plant tissue. Plant species composition was not significantly different among levels of shoreline development. Zinc concentrations were greater in sediments from developed shorelines and may represent an easily measured indicator of shoreline development. Recently accelerating shoreline development in the southeastern USA may alter plant production, nitrogen storage, and sediment metal content in salt marshes. 相似文献
20.
BERNHARD PEREGOVICH ERICH HOOPS VOLKER RACHOLD 《Boreas: An International Journal of Quaternary Research》1999,28(1):205-214
Heavy mineral studies of East Siberian river sediments, Laptev Sea surface sediments, and a sediment core of the western Laptev Sea were carried out in order to reconstruct the pathways of modern and ancient sediment transport from the Siberian hinterland to the Laptev Sea. The modern heavy mineral distribution of Laptev Sea surface sediments reflects mainly the riverine input. While the eastern and central part of the Laptev Sea is dominated by amphibole, which is supplied by the Lena River, the western part is dominated by pyroxene imported from the Siberian Trap basalts by the Khatanga River. The distribution of garnet and opaque minerals is additionally influenced by hydrodynamic processes. As a consequence of their high density, these minerals are predominantly deposited close to the river mouths. Heavy mineral and sedimentological studies of a sediment core of the western Laptev Sea were applied to reconstruct the postglacial history of the shelf area during the last 11 ka. In the lowermost interval of the core (> c. 10 ka), high accumulation rates and a heavy mineral composition similar to that of the modern Khatanga river indicate fluvial conditions. Additionally, the high mica content in this interval may indicate meltwater inflow from the Byrranga mountains. Strong variations in accumulation rates, grain-size distribution, and heavy mineral composition are observed in the time interval between c. 10 and 6 ka, which represents the main transgression of the Laptev Sea shelf. During the uppermost interval (<6 ka), rather stable conditions similar to the modem situation prevailed. 相似文献