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Correlation of side-scan backscatter intensity with grain-size distribution of shelf sediments, New Jersey margin 总被引：2，自引：0，他引：2
The dependence of acoustic backscatter variations on sediment grain-size distribution is examined using a combined analysis
of 95 kHz side-scan data and approx. 300 grab samples from the New Jersey margin. We show that, under well-controlled circumstances,
an unprecedented degree of correlation can be obtained between backscatter intensity and mean grain size. However, backscatter
is disproportionately affected by larger grain sizes. Addition of just a few extra weight percentage of the larger grain sizes
(>4 mm), which in our study is typically represented by more abundant shell hash among the older sediments at greater water
depths, can completely degrade this correlation.
Received: 29 September 1999 / Revision accepted: 14 February 2000 相似文献
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《Marine Geology》2005,216(4):275-296
Recent chirp seismic reflection data combined with multibeam bathymetry, backscatter, and analysis of grab samples and short cores provide evidence of significant recent erosion on the outer New Jersey shelf. The timing of erosion is constrained by two factors: (1) truncation at the seafloor of what is interpreted to be the transgressive ravinement surface at the base of the surficial sand sheet, and (2) truncation of apparently moribund sand ridges along erosional swales oriented parallel to the primary direction of modern bottom flow and oblique to the strike of the sand ridges. These observations place the erosion in a marine setting, post-dating the passage of the shoreface ravinement and the evolution of sand ridges that form initially in the near shore environment. Also truncated by marine erosion are shallowly buried, fluvial channel systems, formed during the Last Glacial Maximum and filled during the transgression, and a regional reflector “R” that is > ∼ 40 kyr. Depths of erosion range from a few meters to > 10 m. The seafloor within eroded areas is often marked by “ribbon” morphology, seen primarily in the backscatter data as areas of alternating high and low backscatter elongated in the direction of primary bottom flow. Ribbons are more occasionally observed in the bathymetry; where observed, crests exhibit low backscatter and troughs exhibit high backscatter. Sampling reveals that the high backscatter areas of the ribbons consist of a trimodal admixture of mud, sand and shell hash, with a bimodal distribution of abraded and unabraded sand grains and microfauna. The shell hash is interpreted to be an erosional lag, while the muds and unabraded grains are, in this non-depositional environment, evidence of recent erosion at the seafloor of previously undisturbed strata. The lower-backscatter areas of the ribbon morphology were found to be a well-sorted medium sand unit only a few 10's of cm thick overlying the shelly/muddy/sandy material. Concentrations of well-rounded gravels and cobbles were also found in eroded areas with very high backscatter, and at least one of these appears to be derived from the base of an eroded fluvial channel. Seafloor reworking over the transgressive evolution of the shelf appears to have switched from sand ridge evolution, which is documented to ∼ 40 m water depth, to more strictly erosional modification at greater water depths. We suggest that this change may be related to the reduction with water depth in the effectiveness of sediment resuspension by waves. Resuspension is a critical factor in the grain size sorting during transport by bottom currents over large bedforms like sand ridges. Otherwise, we speculate, displacement of sand by unidirectional currents will erode the seafloor. 相似文献
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The size (wavelength and height) and the factors influencing the characteristics of subaqueous dunes in the river Scheldt between Antwerp and the Belgian-Dutch border were studied. More than 60 dune clusters (each cluster represented by a mean height and wavelength of mostly 10 to 20 or more observations) were analysed. A very good exponential correlation between dune height and wavelength was observed (r=0.90) which can be described by H
mean=0.0321L
0.918. Length/depth ratios vary between 0.2 and 9, height/depth ratios between 0.25 and 0.01. There was no clear relationship between current velocity and dune size, as dunes of various sizes co-exist at the same current velocities. Twenty-two dunes were sampled and show grain sizes (d50) ranging between 0.1 and 0.7 mm. Seven out of eight large scale dune fields were found in sandy and/or hard bottom (gravel, coarse sand and shell fragments) environments, whereas small and medium dunes were found in muddy sand and sandy mud environments. 相似文献
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Kenneth S. Davis Niall C. Slowey Ingo H. Stender Hannelore Fiedler William R. Bryant Gunther Fechner 《Geo-Marine Letters》1996,16(3):273-278
The relationship between spatial variations of the properties of sea-floor sediments and acoustic backscatter from the surface of the sea floor on the continental shelf off of Panama City, Florida, USA, is investigated using surficial sediment grab samples and digital side-scan sonar data. Acoustic backscatter strength has a high, direct correlation with the mean grain size of the sediments. Acoustic backscatter strength also correlates directly with the carbonate content of the sediments, particularly in medium-and coarse-sand facies, because large, irregularly shaped, carbonate particles affect both the mean grain size of the sediments and the roughness of the surface of the sea floor. 相似文献
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Perinereis aibuhitensis(Grube, 1878) lives in marine sediments of estuary or shoal areas, where substrate has some crucial environmental factors affecting its burrowing and distribution. In order to provide basic data for the habitat selection and suitability evaluations of the artificial aquaculture of P. aibuhitensis, this paper conducted a quantified analysis of its burrowing ability and explored its behavioral preferences in different substrates,including mud(75 μm), fine sand(125–250 μm), medium sand(250–500 μm), coarse sand(500–2 000 μm), gravel(2 000–4 000 μm) and ceramsite(4 000–8 000 μm). The research results revealed that substrate grain size significantly affected the burrowing time, burrowing rate, burrowing depth and distribution rate(P0.01).Moreover, P. aibuhitensis demonstrated preferential selections relating to substrate grain sizes, had higher burrowing ability in ceramsite, mud and fine sand compared with other substrates. The strongest burrowing ability and the highest distribution rate were observed in ceramsite. The study indicated that P. aibuhitensis was sensitive to substrate grain size, which also had an impact on its burrowing process and population distribution.In the natural sea, substrates mainly composed of mud and fine sand are fit for aquaculture and stock enhancement. Based on behavioral preferences and ecological rehabilitation function of P. aibuhitensis, this paper proposes a symbiotic system of marine animals and halophytes, and constructs an ecosystem model of"Marine fish-Halophytes-Perinereis aibuhitensis" with P. aibuhitensis as the link. 相似文献
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近年来, 随着海砂资源需求激增和勘查开发快速发展, 解决海砂调查研究领域中海砂命名混乱的问题迫在眉睫。本文在总结多年海砂调查经验和前人研究成果的基础上, 分析对比已有粒级划分标准和沉积物命名方法的特点, 提出一套适用于海砂的粒级划分标准和命名方法。基于伍登-温特沃斯(Udden-Wentworth)等比制φ值粒级标准, 提出将海砂沉积物粒级划分为砾(>2mm)、砂(2~0.063mm)和泥(<0.063mm)3大类, 二级细分为9小类; 基于优势粒级法思想, 将砾、砂和泥作为三个分类端元, 提出“砾-砂-泥三角图解+砂、砾质沉积物细分命名”的海砂沉积物分类方案, 体现了“对砂、砾质沉积物细化其名, 对泥质沉积物简化其名”的思想。该命名方法直观地反映了海砂的粒级组成和含量, 同时较好地兼顾了海砂命名的沉积学涵义和实际应用需求。 相似文献
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中国东部陆架表层沉积物粒度特征及其沉积环境浅析 总被引：2，自引：0，他引：2
对取自中国东部陆架海的209个表层沉积物样品进行了粒度分析及沉积物类型划分,探讨细颗粒沉积区分布格局与物源和环流体系的关系。结果表明,研究区底质类型主要有砂、粉砂质砂、泥质砂、砂质粉砂、砂质泥、粉砂和泥,个别站位含砾石。表层沉积物以粗颗粒砂质沉积为主,其主要分布在东海中北部、苏北浅滩、北黄海北部,其粒度特征主要为:平均粒径2～4Φ,分选差(分选系数>2),偏态极正偏(2～2.80),峰态很宽至宽(1.60～3.50);细颗粒泥质沉积主要分布在浙江沿岸至长江口外、苏北老黄河口外、南黄海中部、北黄海西南部及黄河口外的渤海海域,其粒度特征主要为:平均粒径6～7Φ,分选差至较差(分选系数1～2.5),偏态负偏(-1.50～-0.33)至近于对称(-0.33～+0.33),峰态很宽(>2.75)。从环流的流向与路径及邻近的河流物源角度,初步探讨了河流输入物质及环流体系对细颗粒沉积物沉积分布格局的影响,并初步推断了细颗粒沉积物的物源及基本输移路径。 相似文献
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Roger F. McLean 《新西兰海洋与淡水研究杂志》2013,47(2):141-164
Two exposed, high‐energy beaches on the Kaikoura coast of New Zealand are composed of sand and gravel derived from a greywacke terrain. Both beaches can be classified as mixed beaches although the sediment varies from dominantly gravel at the ends of the beach to dominantly sand at the centre, through transition zones in which sand and gravel are mixed. Sixty‐four surface samples were analysed for grain size; two sediment parameters, mean grain size (Mz) and sorting (σI), were calculated. A striking feature of the cumulative frequency curves is that both unimodai and bimodal distributions include median sizes over the whole range of sampled material, even though bimodal samples display two strong modes in the sand and gravel grades. The general deficiency lof sediment dn the very coarse sand and granule classes (0 to — 2 F ) noted by numerous authors in many parts of the world is apparent in the poorly‐sorted bimodal samples. However, the best‐sorted samples also occur in these two classes. Mean grain size of samples ranges from medium sand (1.820) to medium pebbles (—4.7 F ), and sorting ranges from very well sorted (0.250) to very poorly sorted (2.69 F ). Mean erain size on the northern beach is significantly greater than on the southern beach, but values of sorting are comparable. The greater mean size on one beach compared with the other is thought to be a function of the grade of material supplied by local rivers; the similarity in sorting presumably reflects the similarity of the processes acting on the two beaches. Mixed sand‐shingle beaches are relatively rare on a world scale but common in New Zealand. Sediment distributions along the Kaikoura beaches do not reveal a regular decrease in size away from the rivers which supply material to shore at present. Instead, the beaches are differentiated into a number of sediment zones composed of either sand, or mixed sand‐gravel, or gravel. On each beach a gravel zone is located furthest from the river outlets. Sorting generally improves toward the Kaikoura Peninsula. Explanations for these trends are not given. Variations in size and sorting across the two beaches do not show a well developed zonation because of the high level of wave energy which continually mixes the material across the beach. 相似文献
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An understanding of the sedimentary environment in relation to its controlling factors is of great importance in coastal geomorphology,ecology,tourism and aquaculture studies.We attempt to deal with this issue,using a case study from the Xincun Lagoon,Hainan Island in southern China.For the study,surficial sediment samples were collected,together with hydrodynamic and bathymetric surveys,during August 2013.Numerical simulation was carried out to obtain high-spatial resolution tidal current data.The sediment samples were analyzed to derive mean grain size,sorting coefficient,skewness and kurtosis,together with the sand,silt and clay contents.The modern sedimentary environments were classified using system cluster and principal component analyses.Grain size analysis reveals that the sediments are characterized by extremely slightly sandy silty mud(ESSSM) and slightly silty sand(SSS),which are distributed in the central lagoon and near-shore shallow water areas,respectively.Mean grain size varies from 0 to 8.0Ф,with an average of 4.6Ф.The silt content is the highest,i.e.,52% on average,with the average contents of sand and clay being 43% and 5%,respectively.There exists a significant correlation between mean size and water depth,suggesting that the surficial sediments become finer with increasing water depth.Cluster analyses reveals two groups of samples.The first group is characterized by mean grain size of more than 5.5Ф,whilst the second group has mean grain size of below 3.5Ф.Further,these groups also have different correlations between mean grain size and the other grain size parameters.In terms of the tidal current,the average values of the root mean square velocity(RMSV) are 7.5 cm/s and 6.9 cm/s on springs and neaps,respectively.For the RMSVs that are higher than 4 cm/s,a significant positive correlation is found between the content of the 63–125 μm fraction and the RMSV,suggesting that the RMSV determines the variability of the very fine sand fraction.Based on system cluster and principal component analyses(PCA),the modern sedimentary environments are classified into three types according to the grain size parameters,RMSVs and water depth data.The results suggest the importance of grain size parameters and high-spatial resolution hydrodynamic data in differentiating the coastal sedimentary environments. 相似文献
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根据北仑河口3个钻孔柱状沉积物的粒度分析结果,结合14C测年和210Pb测年资料,分析了钻孔沉积物的粒度特征,结果表明：KL1柱样沉积物主要为粉砂质砂、砂质粉砂、中细砂、细中砂,沉积物由下到上由细到粗再变细,经历了2个沉积变化;KL2柱样沉积物单一,为细中砂;KL3柱样沉积物由下到上依次为砾石、砂砾、粗中砂、细中砂、砾砂、粉砂质砂、粘土质粉砂、砂-粉砂-粘土,沉积物粒度由下到上逐步细化,该孔早期离物源较近.3个孔的沉积物分选大多很差,反映当时水动力作用较强或者离物源较近.这些沉积物类型为晚更新世末次冰期以来的沉积,记录了晚更新世以来2个沉积变化. 相似文献
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Effects of using inclined parametric echosounding on sub-bottom acoustic imaging and advances in buried object detection 总被引：1，自引：0，他引：1
Jens Schneider von Deimling Philipp Held Peter Feldens Dennis Wilken 《Geo-Marine Letters》2016,36(2):113-119
This study reports an adaptation of a parametric echosounder system using 15 kHz as secondary frequency to investigate the angular response of sub-bottom backscatter strength of layered mud, providing a new method for enhanced acoustic detection of buried targets. Adaptions to achieve both vertical (0°) and non-vertical inclination (1–15°, 30°, 45° and 60°) comprise mechanical tilting of the acoustic transducer and electronic beam steering. Data were acquired at 18 m water depth at a study site characterized by a flat, muddy seafloor where a 0.1 m diameter power cable lies 1–2 m below the seafloor. Surveying the cable with vertical incidence revealed that the buried cable can hardly be discriminated against the backscatter strength of the layered mud. However, the backscatter strength of layered mud decreases strongly at >3±0.5° incidence and the layered mud echo pattern vanishes beyond 5°. As a consequence, the backscatter pattern of the buried cable is very pronounced in acoustic images gathered at 15°, 30°, 45° and 60° incidence. The size of the cable echo pattern increases linearly with incidence. These effects are attributed to reflection loss from layered mud at larger incidence and to the scattering of the 0.1 m diameter buried cable. Data analyses support the visual impression of superior detection of the cable with an up to 2.6-fold increase of the signal-to-noise ratio at 40° incidence compared to the vertical incidence case. 相似文献
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《Marine Geology》2005,214(4):431-449
The dependence of acoustic backscatter on sediment grain size distribution is examined using dual frequency (100 and 410 kHz) sidescan sonar and 22 sediment grab samples from the Loch Linnhe artificial reef site on the west coast of Scotland. The sidescan data were processed to remove an empirically estimated average grazing angle dependence on backscatter. The processed data were analysed by forming histograms of pixels extracted from a 20 m2 box around each ground truth site. A positive correlation (r=0.73) between mean backscatter intensity and mean grain size was obtained, i.e., the coarsest samples had the brightest backscatter. A positive correlation (r=0.59) was also found between the standard deviations of the backscatter and grain size distributions, i.e., poorly sorted sediments gave the most variable backscatter. The performance of the sidescan data was compared to results from a co-incident single-beam echo-sounder RoxAnn survey. The RoxAnn roughness index E1 compared well with the sidescan, whilst the RoxAnn hardness index E2 did not. This may be due to a physical link between the acoustic measures. The comparison showed the sidescan to have delivered a significantly higher-resolution image of the seabed for a similar amount of ship-time. Imaging of the artificial reef modules themselves was found to be frequency dependent. 相似文献
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Stratigraphic models for microtidal tidal deltas; examples from the Florida Gulf coast 总被引：1，自引：0，他引：1
Richard A. Davis Jr. C. Kelly Cuffe Katherine A. Kowalski Eric J. Shock 《Marine Geology》2003,200(1-4):49-60
Extensive vibracoring of both flood- and ebb-tidal deltas along the central Gulf Coast of the Florida peninsula reveals a strong overall similarity with subtle distinctions between flood and ebb varieties. Although the coast in question is microtidal, the inlets range from tide-dominated to distinctly wave-dominated. Both types of tidal deltas overlie a muddy sand interpreted to have been deposited in a back-barrier environment. The sharp contact at the base of the tidal delta sequence is typically overlain by a thin shell gravel layer. The ebb-tidal delta sequence is characterized by fine quartz sand with shell gravel in various concentrations; coarse and massive at the margins of the main ebb channel, and finer and imbricated at the marginal flood channels. The flood-tidal deltas are characterized by the same facies but with a small amount of mud. Shelly facies on the channels on flood deltas are not as well developed as on the ebb deltas. The combination of the stratigraphic sequence and the lithofacies make tidal deltas readily identifiable in the ancient record. The differences between flood and ebb varieties are subtle but consistent. 相似文献
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Abstract. A quantitative survey (18 stations) of the subtidal soft bottom macroinfauna in an estuary of the south Chilean coast was conducted during January, 1980. The map of sedimentological facies elaborated for the Queule River Estuary shows sandy bottoms in the outlet and upper part of the area studied, while the middle part is occupied by muddy sand. The ordination of stations by Principal Component Analysis is fundamentally defined by mud and gravel percentage and is, in general, concordant with the distribution of sediments in the facies map. A total of 17,405 animals was collected (16 taxa), Polychaeta being the dominant group in density (77.47%) and biomass (73.4%). The maximum number of species was obtained outside the mouth of the estuary, while maximum densities and biomass were obtained in the middle of the estuary.
The Factor Analysis performed with the abundances data of the most abundant species rendered the ordination of two groups of stations (concordant with a Cluster Analysis) in the Q-mode and two groups of species in the R-mode. One group of stations is restricted to sandy habitats of the outlet area and is dominated by suspension feeders. The other, in the middle and upper part of the estuary (muddy sand or sandy bottoms with a higher percentage of organic matter), is dominated by deposit feeders. Between these two groups, significant differences in sedimentological variables (sand, mud, and organic matter percentage) were detected. Each of the two delineated groups of species corresponds to the groups of stations, showing that most of the taxa can be combined in faunal assemblages with preference for different types of substrate. 相似文献
The Factor Analysis performed with the abundances data of the most abundant species rendered the ordination of two groups of stations (concordant with a Cluster Analysis) in the Q-mode and two groups of species in the R-mode. One group of stations is restricted to sandy habitats of the outlet area and is dominated by suspension feeders. The other, in the middle and upper part of the estuary (muddy sand or sandy bottoms with a higher percentage of organic matter), is dominated by deposit feeders. Between these two groups, significant differences in sedimentological variables (sand, mud, and organic matter percentage) were detected. Each of the two delineated groups of species corresponds to the groups of stations, showing that most of the taxa can be combined in faunal assemblages with preference for different types of substrate. 相似文献
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Characterization of the sediment composition of tidal flats and monitoring of their spatiotemporal changes has become an important part of the sustainable management of coastal environments. To accurately classify sediments through remote sensing, a comprehensive understanding of sediment reflectance spectra is indispensable. The present laboratory-based study explores the performance of the high spatial resolution (10?×?10 m) Advanced Land Observing Satellite (ALOS) launched in 2006. Relationships between reflectance spectra (bands 1 to 4) and four typical mass physical properties were investigated under wet and dry experimental conditions for intertidal sediments sampled near the Ba Lat Estuary in northern Vietnam. Reflectance in the near-infrared region corresponding to ALOS band 4 (0.76–0.89 μm) was found (1) to have a strong negative correlation with sand content (dry wt%) under both wet and dry conditions (linear correlation coefficient r?=?–0.7859 and –0.8094, respectively), (2) to increase with decreasing relative water content (%) in a given sediment type (r?=?–0.7748 to –0.9367 for mud, sandy mud, muddy sand, and sand), (3) to have a positive correlation with organic matter content (r?=?0.7610 and 0.6460 under wet and dry conditions for contents >0.20 dry wt%), and (4) to be insignificantly correlated with mineral composition assessed in terms of contents (wt%) of quartz, clay minerals, and mica group minerals. Positive relationships between reflectance and water content for the pooled data of all sediment types (r?=?0.6395) or organic matter content contrast with previous findings, and can be attributed to close interrelationships between these properties and the predominance of sand content as controlling factor of reflectance. This study clarifies that ALOS band 4 provides the most useful imagery for intertidal monitoring because its reflectance, as simulated using the laboratory data, shows the strongest correlation with sand content. In a next step, these experimental findings should be verified by identifying the reflectance relationships at satellite image scales, and also considering the effects of other tidal flat features on reflectance, such as microtopography and biological surface characteristics. 相似文献
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The feasibility of an artificial neural network based approach is investigated to estimate the values of mean grain size of
seafloor sediments using four dominant echo features, extracted from acoustic backscatter data. The acoustic backscatter data
were collected using a dual-frequency (33 and 210 kHz) single-beam, normal-incidence echo sounder at twenty locations in the
central part of the western continental shelf of India. Statistically significant correlations are observed between the estimated
average values of mean grain size of sediments and the ground-truth data at both the frequencies. The results indicate that
once a multi-layer perceptron model is trained with back-propagation algorithm, the values of mean grain size can reasonably
be estimated in an experimental area. The study also revealed that the consistency among the estimated values of mean grain
size at different acoustic frequencies is considerably improved with the neural network based method as compared to that with
a model-based approach. 相似文献
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本文通过对黄河三角洲埕岛海域146个表层样的粒度分析,表明该区有5种沉积物类型,以砂质粉砂为主体,呈斑块状分布,极细砂与粗粉砂是沉积物的主要粒级,普遍分选差。运用"粒径趋势"分析的方法,分析探讨了埕岛海域表层沉积物净输运趋势。研究区的沉积物的净输运趋势大致以12 m水深为界,深水区沉积物的净输运趋势向岸,12 m以浅海域的沉积物具有离岸的净输运趋势,说明深水区沉积物受冬季风浪作用向岸运移作用显著,12 m以浅海域的沉积物受夏季风浪作用离岸运移作用显著,沉积物运移的季节变化已成为研究区海域沉积物净运移的主要控制因素。 相似文献