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1.
J. S. Waldner D. W. Hall Jane Uptegrove R. E. Sheridan G. M. Ashley Dominic Esker 《Marine Georesources & Geotechnology》1999,17(2):139-140
Beach replenishment serves the dual purpose of maintaining a source of tourism and recreation while protecting life and property. For New Jersey, sources for beach sand supply are increasingly found offshore. To meet present and future needs, geologic and geophysical techniques can be used to improve the identification, volume estimation, and determination of suitability, thereby making the mining and manag ing of this resource more effective. Current research has improved both data collection and interpretation of seismic surveys and vibracore analysis for projects investigating sand ridges offshore of New Jersey. The New Jersey Geological Survey in cooperation with Rutgers University is evaluating the capabilities of digital seismic data (in addition to analog data) to analyze sand ridges. The printing density of analog systems limits the dynamic range to about 24 dB. Digital acquisition systems with dynamic ranges above 100 dB can permit enhanced seismic profiles by trace static correction, deconvolution, automatic gain scaling, horizontal stacking and digital filtering. Problems common to analog data, such as wave-motion effects of surface sources, water-bottom reverberation, and bubble-pulse-width can be addressed by processing. More than 160 line miles of digital high-resolution continuous profiling seismic data have been collected at sand ridges off Avalon, Beach Haven, and Barnegat Inlet. Digital multichannel data collection has recently been employed to map sand resources within the Port of New York New Jersey expanded dredge-spoil site located 3 mi offshore of Sandy Hook, New Jersey. Multichannel data processing can reduce multiples, improve signal-to-noise calculations, enable source deconvolution, and generate sediment acoustic velocities and acoustic impedance analysis. Synthetic seismograms based on empirical relationships among grain size distribution, density, and velocity from vibracores are used to calculate proxy values for density and velocity. The seismograms are then correlated to the digital seismic profile to confirm reflected events. They are particularly useful where individual reflection events cannot be detected but a waveform generated by several thin lithologic units can be recognized. Progress in application of geologic and geophysical methods provides advan tages in detailed sediment analysis and volumetric estimation of offshore sand ridges. New techniques for current and ongoing beach replenishment projects not only expand our knowledge of the geologic processes involved in sand ridge origin and development, but also improve our assessment of these valuable resources. These reconnaissance studies provide extensive data to the engineer regarding the suitability and quantity of sand and can optimize placement and analysis of vibracore samples. 相似文献
2.
Charles W. Finkl Jr. Syed M. Khalil Jeffrey L. Andrews 《Marine Georesources & Geotechnology》2013,31(2):155-173
Erosion of sandy beaches is a worldwide problem that elicits innovative geoengineer‐ing techniques to reduce adverse impacts of shoreline retreat. Beach replenishment has emerged as the “soft”; shore‐stabilization technique of choice for mitigating beach erosion. This method of shore protection involves the addition of sand to the littoral sediment budget for sacrificial purposes. Because inland sand sources are often uneconomical or impractical to use, and known nearshore sources are limited, finding adequate quantities of suitable sand on the inner continental shelf is often vital to beach replenishment projects. The technical studies of survey and materials analysis that identify and delineate usable sand sources are sometimes almost as expensive as small‐project dredging, pumping, and placing the sand on the beach as fill. Inadequate quantity or substandard quality of shelf sand, as well as often‐prohibitive overhead expenses, thus compel shoreline managers to seek suitable sand sources offshore. In the study area off the central‐west coast of Florida, offshore potential borrow areas (PBAs) were identified on the basis of studies conducted in reconnoitory and detailed phases. Sophisticated state‐of‐the‐art equipment used in this investigation provided more detailed subbottom mapping information than is normally obtained with conventional seismic equipment. An example of sand exploration studies was incorporated in a 215‐km2 survey of offshore areas by conducting bathymetric surveys and subbottom seismic profiling, collecting jet probes, grab samples, and vibrocores, and analyzing sediment grading in subsamples from vibrocores. These combined analyses indicated that at least 8.8 ×106 m3 of sand is available in potential borrow areas from 7.0 to 12 km offshore in water depths of 8.0 to 11.5 m. In the PBAs, mean grain size of sand falls into the range 0.13–0.53 mm, sorting averages 0.65–1.31ø, and the overall silt content varies from 3.9–8.5%. High silt contents (13–19%) mapped in some areas make these sedimentary deposits unsuitable as fill for artificial beach renourishment. 相似文献
3.
Beginning in 1988, the Delaware Geological Survey began a program to inventory on-land sand resources suitable for beach nourishment. The inventory included an assessment of the native beach textures using existing data and developing parameters of what would be considered suitable sand textures for Delaware's Atlantic beaches. An assessment of the economics of on-land sand resources was also conducted, and it was determined that the cost of the sand was competitive with offshore dredging costs. In addition, the sand resources were put into a geologic context for purposes of predicting which depositional environments and lithostrati graphic units were most likely to produce suitable sand resources. The results of the work identified several suitable on-land sand resource areas in the Omar and Beaverdam formations that were deposited in barrier-tidal delta and fluvial-estuarine environments, respectively. The identified on-land resources areas have not been utilized due to difficulties of truck transport and development pressures in the resource areas. The Delaware Geological Survey's participation in years 8, 9, and 10 of the Continental Margins Program was developed to extend the known resource areas onshore to offshore Delaware in order to determine potential offshore sand resources for beach nourishment. Years 8 and 9 involved primarily the collection of all available data on the offshore geology. These data included all seismic lines, surface grab samples, and cores. The data were filtered for those that had reliable locations and geologic information that could be used for geologic investigations. Year 10 completed the investigations onshore by construction of a geologic cross-section from data along the coast of Delaware from Cape Henlopen to Fenwick. This cross section identified the geologic units and potential sand resource bodies as found immediately along the coast. These units and resources are currently being extended offshore and tied to known and potential sand resources as part of the continuing cooperative effort between the Delaware Geological Survey and the Minerals Man agement Service's INTERMAR office as sand resources are identified in federal waters off Delaware. Offshore sand resources are found in the Pliocene Beaverdam Formation offshore where overlying Quaternary units have been stripped, in the tidal delta complexes of several Quaternary units likely equivalent to the onshore Omar Formation, and in late Pleistocene and Holocene-age shoal complexes. Onshore lithostratigraphic units can be traced offshore and show another reason for continued geologic mapping both onshore and offshore. 相似文献
4.
Hee Jun Lee Jong-Dae Do Sun Sin Kim Won-Kyung Park Kicheon Jun 《Ocean Science Journal》2016,51(4):681-694
Haeundae Beach represents Korean pocket beaches that are currently erosional and dominated by summertime typhoons. The decadal wave characteristics 9 km offshore of Haeundae Beach were analyzed using the WAM model that was validated through the 2007 wave observations. The wave statistics modelled for 1979–2007 indicates that the seasonal mean significant wave height (H s ) is highest (0.6–0.7 m) in summer due to typhoons, in contrast to the lowest (around 0.5 m) autumn analog. The wave direction is also pronouncedly seasonal with the principal bearings of SSW and NE in the summer and winter seasons, respectively. The WAM results additionally show that the H s has gradually increased over the region of Haeundae Beach since 1993. Beach profiling during June–November 2014 shows the opposite processes of the typhoon and fair-weather on beach sands. During a typhoon, foreshore sands were eroded and then accumulated as sand bars on the surf zone. In the subsequent fair-weather, the sand bars moved back to the beach resulting in the surf-zone erosion and foreshore accretion. A total of 5 cycles of these beach-wide sand movements yielded a net retreat (up to 20 m) of the shoreline associated with large foreshore erosion. However, the surf zone only slightly accumulated as a result of the sand cycles. This was attributed to the sand escape offshore from the westernmost tip of the beach. The present study may provide an important clue to understanding the erosional processes in Haeundae Beach. 相似文献
5.
随着全球海平面的上升及极端气象的频发,全球海滩总体呈现出一定的退化现象,海滩保护成为海岸带生态修复的焦点问题之一。我国华南地区岬湾型海滩分布广泛,以深圳市大鹏湾官湖海滩为代表,基于2020—2021年实测海滩剖面高程数据,分析岬湾型海滩季节性变化特征。研究表明,官湖海滩剖面坡度夏秋缓冬春陡,夏秋侵蚀冬春淤积;海滩沉积物粒径季节性变化不明显。海滩剖面形态受风浪、平均潮位的季节性变化控制,以夏秋季为例,平均潮位逐渐升高,南向波浪强度较大,在二者的共同作用下,海滩后滨侵蚀明显,泥沙离岸输运,并在前滨淤积。补沙方案宜在夏秋季进行,且重点区域为官湖海滩东侧与观海湾海滩,防御方案应主要削弱南向波浪。 相似文献
6.
7.
根据2011年在海阳万米海滩岸段与威海国际海水浴场岸段调查获得的夏、冬两季海岸实测地形剖面与沉积物粒度数据,并收集相关水文资料,对南北两海岸地貌与沉积差异性进行分析,探讨了半岛东部南北岸典型砂质海岸动力环境的差异。研究结果表明,南部海岸宽广平缓,发育滩脊、滩肩、沙波纹等地貌,沉积物在水下岸坡上段以中粗砂、中细砂为主,水下岸坡以下段以粉砂、黏土质粉砂为主;北部海岸地形陡,发育滩肩陡坎、水下沙坝等地貌,沉积物以砾质砂为主。导致这些差异的动力为风、波浪、潮汐及沿岸流堆积。 相似文献
8.
Cross-ridge grain size profiles were determined for a nearshore and an offshore sand ridge on the New Jersey shelf. On both,
the coarset sands occur on the landward flank. The range and rate of change in grain size with horizontal distance are greatest
on the nearshore ridge. The grain size gradient is believed to be a response of the bottom to the cross-ridge shear stress
distribution during storm flows. The difference between the two ridges may be a consequence of the relict origin of the offshore
ridge versus a modern origin for the nearshore ridge, or to the different flow climates of the nearshore and offshore environments. 相似文献
9.
美国东岸,自纽约长岛经马里兰、新泽西直至弗罗里达基本属于沙坝渴湖岸,岸外的内、外陆架上分布一系列水下沙脊及脊间沙带、沙丘和沙波等次一级底形。按新泽西岸外20-80m水深处35个沙脊的统计,脊长约2～11km,宽约1～4km,长宽比界于2：1～3：1之间,与世界典型沙脊长宽比40：1比较,本区沙脊属于短轴浪控型,脊高约1～3m,或者更高。向NE10°～30°伸展,两坡不对称,上游坡平缓,下游坡较陡,约2．5°～7．0°。按34-48m水深处的“黄金沙脊”上的20余钻孔岩心分析和HC年龄测试,划分沙脊自下而上3层地层：9～11kaBP以前的平原陆相层;9—5kaBP的下部沙脊沙层;5kaBP以来的上部沙脊沙层。上部沙脊层不断向下游SE侧超越迁移,局部定位观测的沙脊迁移率为1～2m／a。 相似文献
10.
Charles L. Morgan James H. Barry Jr. Michael J. Cruickshank 《Marine Georesources & Geotechnology》2013,31(1):75-94
Researchers at the University of Hawai'i at Manoa have been working for the past several years to develop the necessary techniques for finding and quantitatively characterizing offshore unconsolidated carbonate deposits with potential for beach nourishment and use in construction aggregates for tropical island communities. This article examines particular results of this research, with special attention given to the area offshore from Waikiki Beach. Acoustic surveying, water‐jet probing to measure the thickness of unconsolidated material and three different sampling methods were used in this study. Two separate seismic systems were used for the subbottom profiling survey, a Datasonics Bubble‐Pulser® system and a broad‐band, frequency‐modulated ("chirp") prototype system. The following conclusions were reached. (1) Many different types of sediment underlie tropical island carbonate sand deposits and serve as refusing horizons to jet probing. Examples include consolidated or unconsolidated reef debris, beach rock, cemented sand, and various types of conglomerates formed from rhodoliths (coralline algae) or reef detritus. (2) Massive coral growth over clastic deposits is not a common offshore feature in this area, though it does occur in some areas off the Reef Runway. (3) Matrices of the coral Porites compressa, in‐filled with sand, may have acoustic properties similar to those of the sand bodies. Such deposits may be difficult to distinguish from unconsolidated deposits from seismic records alone. (4) Significant new prospects for offshore aggregates were found in the insular shelf offshore from Southern O'ahu. A total of 5,100,000 m3 were mapped off Waikiki. The Makua Shelf deposits in this area presently appear to be the best prospects for commercial development. 相似文献
11.
广西北海银滩侵蚀动力研究 总被引：1，自引：0，他引：1
广西北海银滩是一处典型的强潮海滩，以滩面宽阔、砂质纯白为特征，为当地的一处著名旅游景点。近年来银滩也出现了岸线后退、滩肩消失、沉积粗化等侵蚀迹象。为了研究银滩侵蚀的动力机制，本文对银滩海水浴场当前的滩面高程、坡度以及滩面后退距离特征进行了调查和分析。并基于2016?2018年间的滩面高程动态变化，分析了冬、春季风浪和台风期间水位、波浪特征与滩面侵蚀之间的关系，并进而探讨了最有可能造成银滩侵蚀的台风路径。研究表明，1985年以来的滩面最大后退距离为80 m，侵蚀造成海滩上部滩面坡度降低，使得海滩上部的剖面形态向上凸状转化。冬、春季节的风浪叠加高水位可能会造成一定程度的滩面侵蚀，并在海滩上部形成脊槽地貌，但是这种侵蚀会被夏季西南向涌浪导致的回淤所恢复。造成银滩侵蚀后退的主要原因是2003年以来风暴潮重现频率增加。发源于西太平洋，经海南岛北部或雷州半岛进入北部湾的台风可以导致显著的海岸增水，最易于引起强烈的海滩侵蚀事件。银滩东侧的渔港码头阻断了自东向西的泥沙沿岸净输运，也是加剧银滩侵蚀的重要因素。 相似文献
12.
海平面变化及其海岸响应 总被引：4，自引：0，他引：4
第四纪气温的大幅度冷暖变化，导致全球海平面的变化，引起陆架海侵扣海退。海岸上的各种地貌如海滩、沙坝、三角洲扣陆架沙脊等响应海平面升降而发生新的演化扣变异。东海陆架古岸线、围绕古岸线发育的陆架沙脊、陆架深切河谷扣河谷充填沉积以及冰后期海进型扣海退型沙坝的形成乖演化等沉积事件都是响应海平面升降的结果。近百年来特别是近30年全球海平面普遍上升，引起风暴潮的频度扣幅度的增大。近岸波能增强，越滩浪增多，导致海滩侵蚀，岸线后退。Bruun法则扣其他一些模型能够说明海滩随海平面上升而蚀退的规律，但在预测速率时仍存在很多问题。使用时应注意海平面变化的区域性、海滩发育的滞后性和海滩蚀退因素间的权重关系。 相似文献
13.
海滩养护过程和工程技术 总被引：1，自引：0，他引：1
海滩养护是根据设计方案,向海滩大量抛沙,或者同时辅以硬工程,使受蚀海滩增宽和稳足的工程,是抵御海岸侵袭灾害的最佳措施。上世纪末发达国家已普遍开展,我国目前尚属起步,但近年发展迅速。该工程分调查,重建和修补3个阶段,三者相互补充和制约。重建前必须充分调查目标岸段,以为设计养护方案提供依据;重建阶段应注重抛沙位置、沙成分、抛沙量和沙源选择等工序;重建后应进行多年的剖面监测和再抛沙的修补。在那些浪大,沙少和岩礁裸露的侵蚀岸段,应辅以丁坝或岸外潜坝等硬工程加以抵浪,维持所填沙的稳定。 相似文献
14.
Stratigraphic framework of sediment-starved sand ridges on a mixed siliciclastic/carbonate inner shelf; west-central Florida 总被引：1，自引：0，他引：1
J. H. Edwards S. E. Harrison S. D. Locker A. C. Hine D. C. Twichell 《Marine Geology》2003,200(1-4):195-217
Seismic reflection profiles and vibracores have revealed that an inner shelf, sand-ridge field has developed over the past few thousand years situated on an elevated, broad bedrock terrace. This terrace extends seaward of a major headland associated with the modern barrier-island coastline of west-central Florida. The overall geologic setting is a low-energy, sediment-starved, mixed siliciclastic/carbonate inner continental shelf supporting a thin sedimentary veneer. This veneer is arranged in a series of subparallel, shore-oblique, and to a minor extent, shore-parallel sand ridges. Seven major facies are present beneath the ridges, including a basal Neogene limestone gravel facies and a blue-green clay facies indicative of dominantly authigenic sedimentation. A major sequence boundary separates these older units from Holocene age, organic-rich mud facies (marsh), which grades upward into a muddy sand facies (lagoon or shallow open shelf/seagrass meadows). Cores reveal that the muddy shelf facies is either in sharp contact or grades upward into a shelly sand facies (ravinement or sudden termination of seagrass meadows). The shelly sand facies grades upward to a mixed siliciclastic/carbonate facies, which forms the sand ridges themselves. This mixed siliciclastic/carbonate facies differs from the sediment on the beach and shoreface, suggesting insignificant sediment exchange between the offshore ridges and the modern coastline. Additionally, the lack of early Holocene, pre-ridge facies in the troughs between the ridges suggests that the ridges themselves do not migrate laterally extensively. Radiocarbon dating has indicated that these sand ridges can form relatively quickly (1.3 ka) on relatively low-energy inner shelves once open-marine conditions are available, and that frequent, high-energy, storm-dominated conditions are not necessarily required. We suggest that the two inner shelf depositional models presented (open-shelf vs. migrating barrier-island) may have co-existed spatially and/or temporally to explain the distribution of facies and vertical facies contacts. 相似文献
15.
为阐明珠三坳陷西北部珠江组一段上亚段浅海陆架砂体成因机制,综合地质与地球物理数据,首先搭建了五级层序地层格架,并以此为约束,开展浅海陆架砂体识别与定量描述,剖析其时空演化规律,进而讨论其成因机制。结果表明：（1）研究区珠江组一段上亚段可划分为4个五级层序,自下向上编号为FS4、FS3、FS2与FS1;(2)研究区发育潮流沙脊与滨外沙坝两种类型陆架砂体,两者整体呈NW-SE向展布,潮流沙脊主要分布于研究区西部,滨外沙坝则集中于东部;（3）FS4、FS3与FS2 3个五级层序中,潮流沙脊与滨外沙坝均呈现较大规模与较多数量,最上部FS1五级层序中,规模与数量达到最小;（4）沉积基准面（水动力）、同沉积地貌、沉积物碎屑供给等因素共同影响了潮流沙脊与滨外沙坝的发育规模、展布特征与时空演化规律等,综合构成了珠三坳陷西北部浅海陆架砂体的成因机制。 相似文献
16.
极端高能事件影响下的海滩动力地貌过程直接关乎岸滩稳定及海堤安全。本文基于2020年16号台风“浪卡”前后北海银滩顺直岸段的剖面高程及表层沉积物等资料, 探究了中等潮差的顺直响应台风作用的地貌变化机制。结果表明: 1) 台风后海滩地貌表现为冲流带的大型沙坝消失, 后滨沙丘-滩槽体系被削平, 滩面坡度趋于平缓。2) 银滩沉积物均以中砂、细砂和极细砂为主, 三者占比超过95%; 台风后, 高潮位带沉积物变细, 低潮位带沉积物变粗, 沙坝附近则出现粗细交错式变化; 银滩中高潮位带滩面响应台风过程的特征与强潮型海滩相似, 呈现消散型海滩的特征, 而低潮位带滩面则因大型沙坝的作用而呈现弱潮型海滩特征。3) 台风期间波浪是影响海滩的主要动力因素, 海滩地形影响了近岸水动力的表现形式, 从而改变了沉积物的粒径分布。 相似文献
17.
长久以来,人们采用各咎护岸工程保护遭受侵蚀的岸段,却忽视了由这些护岸建筑引起的负面效应－－干坝、突堤、离岸堤可导致邻近岸段的蚀退;海提、护岸至少经岸下蚀;海滩的人工再塑难以解决沙源,一个护岸工程,不仅要在工程上可行,还应地周边环境产生负面影响,本文就此提出了几点建议。 相似文献
18.
探测查明海砂分布及其资源量, 对海洋矿产资源规划和社会经济发展有重要意义。利用在中国台湾浅滩采集的单波束测深、侧扫声呐、浅地层剖面、单道地震等多源地球物理数据, 识别出海底沙脊、沙波、埋藏古河道等有利于海砂赋存的地貌标志, 以及厚泥盖层等不利标志, 它们在平面上渐变交错分布。地球物理数据与表层沉积物、钻孔岩心结果对比, 证实浅地层剖面能有效识别表层砂体上部和排除厚泥盖层(厚度>10m), 表层砂体上部呈断续中弱振幅杂乱反射; 单道地震剖面能有效识别砂-泥地层界面, 垂向上刻画表层及埋藏砂体形态, 砂体最主要的特征为连续性差的弱振幅反射中夹杂空白、杂乱的“白雾”反射。砂体响应特征反映了砂体声学较难穿透的特性, 同时也可能是砂体含气所致。分析表明在砂体形态多变或钻孔分布密度低时, 利用地球物理方法, 结合一定数量的钻孔岩心约束, 相比仅依靠大量钻孔岩心, 可更为经济、高效地对砂体的垂向形态和平面展布进行精细刻画, 从而有利于更准确地估算海砂的资源量。 相似文献
19.
为了研究蓬莱西庄海岸侵蚀原因、揭示泥沙运移规律，利用萤光示踪砂和染色砾石进行侵蚀岸段的泥沙示踪研究．其主要结果如下：１．海滩泥沙运动完全由波浪控制，泥沙运移的速度和方向取决于破波的大小和方向．２．海滩泥沙以群体形式沿岸输移．３．在平直海岸上，泥沙可超越粘土质海蚀平台进入另一砂质海滩。 相似文献
20.
The marine geological map n. 502 “Agropoli”, located offshore the Cilento Promontory, southern Italy, is here described and the regional geology interpreted, particularly referring to water depths between the 30 and 200 m isobaths. The geologic map has been constructed in the frame of a research program financed by the National Geological Survey of Italy (CARG Project), finalized to the construction of up-to-date cartography of the Campania region. Geological and geophysical data on the continental shelf and slope offshore of the Southern Campania region have been collected in the study area, bounded northwards by the Salerno Gulf and southwards by the Policastro Gulf. A high resolution multibeam bathymetry allowed for the construction of a marine digital elevation map; sidescan sonar profiles also have been collected and interpreted. The latter, merged to the bathymetry, have represented the base for the marine geologic cartography. The integrated geologic interpretation of seismic, bathymetric and sidescan sonar data has been calibrated by sea-bottom samples. The morpho-structures and the seismic sequences overlying the outcrops of acoustic basement reported in the cartographic representation have been studied in detail using single-channel seismics. The interpretation of seismic profiles has been a support for the reconstruction of the stratigraphic and structural setting of the Quaternary continental shelf successions and the outcrops of rocky acoustic basement in correspondence to the Licosa Cape morpho-structural high. These areas result from the seaward prolongation of the stratigraphic and structural units, widely cropping out in the surrounding emerged sector of the Cilento Promontory. The cartographic approach is based on the recognition of laterally coeval depositional systems, interpreted in the frame of the system tracts of the Late Quaternary depositional sequence. We present evidence of now subaqueous terraces inferred to be palaeoshorelines representing past sea-level positions and tentatively correlated these to oxygen isotopic stratigraphy. 相似文献