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1.
北部湾大风江与南流江河口红树林空间分布格局研究 总被引：1，自引：1，他引：0
生长在潮间带的红树植物在河口植物群落构成、海岸防风消浪中具有重要价值。本文基于本地种桐花树胚胎浸泡下沉实验与北部湾南流江和大风江河口段水体盐度、沿线潮间带植物群落结构与地貌分析,探讨红树林在河口空间分布及影响因素。结果主要表明:南流江河口和大风江河口红树林自海向陆基本展现“红树林纯林(桐花树、秋茄、无瓣海桑种类混生)→红树植物与半红树植物(黄槿、苦朗等)混生→红树植物、半红树植物与非红树植物混生→红树植物镶嵌→稀疏红树林小苗”的分布格局,但大风江河口向陆界限主要以红树、红树幼苗及半红树混生为主。此外,红树被浸淹时长是控制河口红树空间分布结构的主要因素。潮水上溯时长影响红树向陆生长的极限位置,宜林滩地是红树发育生长的必要条件。 相似文献
2.
Twelve washover deposits were cored on the west-central Gulf Coast of Florida to provide data to permit development of a model to help identify washover facies in the stratigraphic record. Typical modern washover stratigraphy displays landward-dipping plane beds comprised of well-sorted sand with distinct laminae of shells and heavy minerals. Five subfacies are delineated which show variations in composition, texture, and bioturbation throughout the washover facies. These subfacies represent differences in flow conditions during overwash, position relative to sea level, and variable degrees of reworking after deposition. Three shell assemblages aid in identification of washover deposits. Backbarrier sediments composed of shoreface/open water species or mixed shoreface/backbarrier species may potentially be washover in origin. Sediments with purely backbarrier/quiet water shell species are likely to have been deposited independently of washover activity. Examination of washover deposits of differing ages reveals that preservation of washover stratigraphy is not exclusively a function of time. Reworking of small-scale stratification can occur in as short as a decade; however, this same stratification was found to be preserved in deposits several hundred years old. Destruction of original washover signatures is related to the position of the deposits relative to sea level, and the rate and depth of burial. Even after the destruction of small-scale stratigraphic features, washover deposits may still be identified as such due to their texture, composition, and shell assemblages. Key features in recognizing the facies after bioturbation and reworking are: (1) the presence of clean sand in otherwise muddy backbarrier sediments, (2) the landward thinning of the facies, and (3) the presence of shoreface shells or mixed shoreface/backbarrier shells on landward portions of the barrier island system. If reworking is severe and/or there are limited subsurface data, distinguishing washovers from genetically similar deposits (e.g. flood tidal deltas and spillover deposits) in the stratigraphic record is difficult and when considered out of stratigraphic context may not be recognizable. 相似文献
3.
Richard A. Davis Jr. Kristin E. Yale John M. Pekala Megan V. Hamilton 《Marine Geology》2003,200(1-4):103-123
Although the morphology of the barrier-inlet system along the west-central Florida coast is quite complicated, the stratigraphy of these barriers is rather simple. The basal Holocene unit in most cores is an organic-rich, muddy sand that represents a vegetated, paralic marine, coastal environment similar to that which is north and south of the present barrier system. Above that unit is a muddy, bioturbated sand that displays a marine fauna at most locations but also contains Crassostrea virginica in a few places. These sediments accumulated in a low-energy marine setting that may or may not have been protected by a barrier island. Much of this facies also represents sediment that was delivered as washover deposits in an intertidal or subtidal setting and was subsequently bioturbated. The facies that can be attributed to a barrier island with some certainty are no more than 3000 years old, and on most islands, are much younger. These are the shelly sand and sorted sand facies. The shelly strata represent deposition in nearshore, beach, supratidal washover or intertidal spillover environments, and tidal inlet and tidal delta channels, whereas the sorted sand is typical of eolian deposition in dunes or the backbeach and some tidal delta elements. The presence of Holocene oyster beds offshore of a present barrier suggests that some of these islands formed significantly offshore and moved to their present position through washover. It is likely that most of these barriers initially formed through upward shoaling by waves. Although there is significant morphologic difference between the wave-dominated and mixed-energy, drumstick barrier islands, their stratigraphy is quite similar. The only significant difference is the presence of extensive progradation on at least part of the drumstick islands and a relatively high amount of former washover deposits on the wave-dominated type. 相似文献
4.
Typical of glaciated environments, the inner continental shelf of New Hampshire is composed of bedrock outcrops, remnants of glacial deposits (for example, drumlins), sand and gravel deposits, as well as muddier sediments farther offshore. A number of previous studies have defined the general trends of the New Hampshire inner shelf from the coarser deposits nearer the shore to the muddier outer basins. Most recently, a seismic survey (150 km of side-scan sonar and subbottom seismic profiles), as well as bottom sediment sampling (74 stations), has provided a detailed bottom map of the southern New Hampshire shelf area (landward of the 30-m contour). The surficial sediments within this area range from very fine sand to gravel. Bedrock outcrops are common. The seismic survey indicated several large sand deposits exceeding 6-8 m in thickness that occur relatively close to the coast. These sedimentary units, which are within 3 km of the shoreline, are composed of fine to medium sands. Examination of the general morphology and depositional setting indicates at least some of these features are probably relic ebb tidal delta shoals. However, a large eroding drumlin occurs between two of the sand bodies and may represent the source of these deposits. Additional work is needed to verify the origin of these sediment bodies. 相似文献
5.
Silvia Albarracín Javier Alcántara-Carrió Andrés Barranco María José Sánchez García Ángela Fontán Bouzas Jorge Rey Salgado 《Geo-Marine Letters》2013,33(2-3):217-223
The focus of this study is the analysis of coastal sand barriers and associated coastal lagoons on the inner continental shelf of the Gulf of Valencia (western Mediterranean), based on two W–E seismic profiles recorded seaward of the Albufera de Valencia coastal lagoon. Seismic facies identified include a number of coastal sand barriers with landward lagoons draped by contemporary continental shelf deposits. The barrier systems have been grouped into two sedimentary systems tracts, the older one corresponding to a prograding/aggrading highstand systems tract involving at least four paleo-coastal sand barrier/lagoon systems, followed landward by a transgressive systems tract comprising three such systems. All the systems have been allocated a Tyrrhenian age, the formation of individual barrier systems having been associated with successive sea-level stillstands, and their present-day position being explained by the very high regional subsidence rate. In summary, this study demonstrates that the Quaternary stratigraphic record of the Gulf of Valencia inner continental shelf is composed of littoral sand facies, in particular coastal sand barrier and lagoon deposits. These findings are in agreement with corresponding observations on other continental shelves of the western Mediterranean, showing that the formation of coastal sand barriers was a characteristic feature of this region during the Quaternary. 相似文献
6.
S.Duncan Heron Jr. Thomas F. Moslow William M. Berelson John R. Herbert George A. Steele III Kenneth R. Susman 《Marine Geology》1984,60(1-4):413-434
The sedimentary record of 130 km of microtidal (0.9 m tidal range) high wave energy (1.5 m average wave height) barrier island shoreline of the Cape Lookout cuspate foreland has been evaluated through examination of 3136 m of subsurface samples from closely spaced drill holes. Holocene sedimentation and coastal evolution has been a function of five major depositional processes: (1) eustatic sea-level rise and barrier-shoreline transgression; (2) lateral tidal inlet migration and reworking of barrier island deposits; (3) shoreface sedimentation and local barrier progradation; (4) storm washover deposition with infilling of shallow lagoons; and (5) flood-tidal delta sedimentation in back-barrier environments.
Twenty-five radiocarbon dates of subsurface peat and shell material from the Cape Lookout area are the basis for a late Holocene sea-level curve. From 9000 to 4000 B.P. eustatic sea level rose rapidly, resulting in landward migration of both barrier limbs of the cuspate foreland. A decline in the rate of sea-level rise since 4000 B.P. resulted in relative shoreline stabilization and deposition of contrasting coastal sedimentary sequences. The higher energy, storm-dominated northeast barrier limb (Core and Portsmouth Banks) has migrated landward producing a transgressive sequence of coarse-grained, horizontally bedded washover sands overlying burrowed to laminated back-barrier and lagoonal silty sands. Locally, ephemeral tidal inlets have reworked the transgressive barrier sequence depositing fining-upward spit platform and channel-fill sequences of cross-bedded, pebble gravel to fine sand and shell. Shoreface sedimentation along a portion of the lower energy, northwest barrier limb (Bogue Banks) has resulted in shoreline progradation and deposition of a coarsening-up sequence of burrowed to cross-bedded and laminated, fine-grained shoreface and foreshore sands. In contrast, the adjacent barrier island (Shackleford Banks) consists almost totally of inlet-fill sediments deposited by lateral tidal inlet migration. Holocene sediments in the shallow lagoons behind the barriers are 5–8 m thick fining-up sequences of interbedded burrowed, rooted and laminated flood-tidal delta, salt marsh, and washover sands, silts and clays.
While barrier island sequences are generally 10 m in thickness, inlet-fill sequences may be as much as 25 m thick and comprise an average of 35% of the Holocene sedimentary deposits. Tidal inlet-fill, back-barrier (including flood-tidal delta) and shoreface deposits are the most highly preservable facies in the wave-dominated barrier-shoreline setting. In the Cape Lookout cuspate foreland, these three facies account for over 80% of the sedimentary deposits preserved beneath the barriers. Foreshore, spit platform and overwash facies account for the remaining 20%. 相似文献
7.
《Marine Geology》2007,236(1-2):45-59
Titanomagnetite forms rich placer deposits along the northwest coast of New Zealand. These deposits were sampled along 3 shore-normal transects spaced over the southern 2 km of a dissipative high-energy beach on the west coast in 5 field campaigns covering one year. The percentage of opaque minerals (mainly titanomagnetite) was extremely high in the upper 30 m of the beach face, extending seaward where these opaque minerals were gradually replaced with variable amounts of lighter augite, hornblende and plagioclase. The pattern appeared to be divided into two regions, a lower seaward and an upper landward region, separated by a point where either marine dominated over aeolian processes or where swash dominated over breaking processes. In the seaward region, the percentage of opaques increased and particle size fined landward as undertow removed the lighter larger particles seaward. In the landward region, the percentage of opaques and particle size were more constant, or even showed the reverse pattern as wind transported the lighter material shoreward, or swash asymmetry transported the heavier material seaward. The similarity of settling velocities over the whole beach face suggests that sorting by size rather than weight plays a dominant role in separating the mineral assemblages. Considerable variations existed between transects. This could be explained by the spatial changes in surfzone waves and currents that were associated with proximity to the southern headland and various rip current channels that characterised this dissipative site. Surprisingly, the percentage of opaques decreased when the wave conditions of the day of sampling were more energetic. In contrast to many other placer deposits, these deposits are abundant on the beach face, forming an armouring layer during lower wave energy conditions. During higher wave conditions, the surface layer erodes allowing lighter augite, plagioclase and hornblende to be released from the sediments below. 相似文献
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9.
对2007年采自越南红河水下三角洲北区24个表层沉积物样品进行了粒度分析和粒度参数计算,初步探讨了该区沉积物的主要类型及分布特征。结果表明,越南红河水下三角洲北区的表层沉积物主要由粉砂组成(体积平均含量为54.35%),平均粒径为6φ。按Link沉积物命名法,该区沉积物主要类型有砂、砂质粉砂和黏土质粉砂。水平分布上,由西部的砂向东逐渐变为黏土质粉砂,呈现出由近岸三角洲前缘相的粗粒级沉积物逐渐向前三角洲-浅海相的细粒级沉积物变化的趋势。与前人研究成果对比发现,红河水下三角洲北区沉积物黏土的比例较1996年的比例明显增大,可能与海岸线近10a来总体上呈向陆迁移、水下三角洲沉积向岸蚀退以及纵向上水动力逐渐变弱有关。 相似文献
10.
G.K. Furnes 《Marine Geology》1974,16(3):145-160
Assuming that the long waves of sand found in sea beds are generated by stationary internal waves, a simplified analysis is made of their stability. The fluid model considered is two-dimensional and two-layered, with the lower layer stratified due to suspended sediments. Finally, the effect of flow over developed sand waves is studied under homogeneous conditions. 相似文献
11.
《Coastal Engineering》1988,12(1):43-62
The process of sediment transport by nonbreaking waves over horizontal, rippled beds is presented by three different models which are evaluated through comparison with wave flume data. The conclusion from this testing is “the simpler the better”. It is shown that the process in question can in fact be modelled adequately without quantitative consideration of the suspended sediment distribution. Only a reference average concentration at the bed is needed. On the other hand, classical diffusion models severely underpredict the transport of coarse sand in suspension because the process is much more organized than diffusion. The possibility of adapting the models to conditions involving sheet flow and/or breaking waves is discussed. 相似文献
12.
T.K. Mallik 《Marine Geology》1976,20(1):57-75
The Lakshadweep are a group of coral atolls enclosing lagoons and submerged reefs and banks in the Arabian Sea off the western coast of India. The sediments in the lagoons consist of corals, halimeda, shells of gastropods, pelecypods, foraminifera, ostracods, etc. derived from the breaking up of the reefs by mechanical processes such as waves, winds, currents, etc. To study the grain-size characteristics of these calcareous sediments in the lagoons, 50 samples were analysed and the grain-size parameters were calculated. The mean of the samples range from ?1.538 to 2.161, standard deviation from 0.935 to 1.859, skewness from ?1.051 to 1.635 and kurtosis from 2.068 to 4.402. The sediments range from coarse sand and gravel to very fine sand size in general and usually are well sorted. A bimodal to polymodal character is present in the sediments due to mixing of a number of heterogeneous constituents. The coarser sediments consist of corals and a good amount of halimeda occurs in the 0 (1 mm) to ?1 (2 mm) phi class. Foraminifera predominantly occur in the interval 1 (0.5 mm) to 0 (1 mm) phi. In the range 1 (0.5 mm) to 2 (0.25 mm) phi, corals are again important, while in the sizes finer than 2 phi (0.25 mm), all the constituents predominate. The size distribution was compared with those obtained at other places such as Barracuda Keys, Gulf of Aqaba, Isla Perez and Lower Florida Keys. The present grain-size variation is not only controlled by the composition of the calcareous sediments but is also modified by the different transporting agents, such as waves, winds, currents, etc. Different energy conditions also exist in the lagoon. Mean transport direction seems to be roughly towards the SSE and saltation is an important mode of transport. 相似文献
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14.
《Marine Geology》2005,219(4):235-259
This paper deals with the sedimentary facies and evolution of the Qiantang River (QR) estuary, and the characteristics and formation of the incised valley sequences and the related shallow biogenic gas reservoir, on the basis of analysis of over 500 cores.The result shows that, since the last glaciation, the Late Quaternary formation of the QR estuary area underwent three stages: (1) deep-cutting stage; (2) rapid-filling stage; and (3) burial stage. The fall of global sea level during the last glacial maximum enhanced the fluvial gradient and river cutting, resulting in the formation of the large-scale QR and Taihu incised valleys, with the interfluve being exposed to air on both flanks of the incised valley. Fluvial terraces at the elevations are present near the present QR estuarine mouth, corresponding to 60–70, 90–100 and 115–125 m burial depths. The valleys were filled rapidly with fluvial sediments during the post-glacial period; with the rise of sea level, the river mouth migrated to landward, and backwater and retrogressive aggradation was enhanced. The QR and Taihu incised valleys are associated with an early filling and transgressive channel-infilling sequence formation, and a late filling and transgressive floodplain-estuary formation. Subsequently, the QR valley was buried under estuarine-marine and estuarine sand bar sediments. From bottom to top, the incised valley successions can be grouped into four sedimentary facies: river channel, floodplain-estuary, estuary-shallow marine, and estuary sand bar.The thickness of the river channel-infilling deposits is controlled mainly by base level rising, backwater, retrogressive aggradation and neotectonism. Further, localized thickening took place where deeper scour pools were present in the incised valley or fluvial terraces were formed during the fall of elative sea level.During the deposition of the floodplain-estuary facies, the conditions of sea level rise, tidal regime, sediment supply and accommodation space were suitable for the development of a tidal ridge system; the sand lenses associated with this facies may represent a tidal ridge system in the incised valley. At the later stage when the estuarine sand bars were formed, the sedimentary conditions were no longer favourable, resulting in absence of sand ridge deposits. Biogenic gas is stored in the floodplain-estuary sand lenses of the incised valleys. The Changjiang River provides the major sediment supply for the QR estuary sand bar, and the QR carried sediments constitute only a small portion of the deposits. 相似文献
15.
S. Srinivasalu N. Thangadurai Adam D. Switzer V. Ram Mohan T. Ayyamperumal 《Marine Geology》2007,240(1-4):65-75
Laterally extensive sand sheets deposited by the 26th December 2004 Asian tsunami provide a valuable modern analogue for comparison with wash over deposits of unknown origin. In many places on the east coast of India, distinct deposits of marine sand drape the landscape and overlie the muddy soils of the coastal plain. This paper discusses detailed measurements of coastal topography, tsunami flow height, and deposit thickness made at Kalpakkam, India. Five transects were examined in detail to assess the sedimentology and spatial distribution of the tsunami deposit. Near the mean water line, the tsunami eroded approximately 10–25 cm of sand from the beach and berm. At Kalpakkam the sand sheet deposited by the tsunami begins 25 m from the shore extending 420 m inland where it becomes thin and patchy approximately 30 m from the limit of inundation. In some cases, the deposit consists of 2 to 4 normally graded units, with coarse sand near the base and fine sand at the top, a characteristic observed in many tsunami deposits worldwide. In many places, the deposits also contain numerous thin laminated units, a characteristic usually associated with storm over wash. The presence of the laminated beds is indicative of the complexity of tsunami sedimentation on the coast. Such observations are essential to the formation of definitive facies models for palaeo-overwash studies that are capable of distinguishing between sediments deposited by storms or tsunami. 相似文献
16.
Shusaku Goto Tomonobu Mizoguchi Ryo Kimura Masataka Kinoshita Makoto Yamano Hideki Hamamoto 《Marine Geophysical Researches》2012,33(3):269-283
We investigated the relationship between variations in the thermal conductivity of surface sediments and the topography in the Nankai subduction zone off Tokai, central Japan, the easternmost part of the Nankai subduction zone, which has an accretionary prism with varied topography. We analyzed sediment thermal conductivity data obtained from the trough floor and accretionary prism. Variations in the thermal conductivity of sediments were related to the topographic features formed by accretionary prism development. Thermal conductivities of 1.1?W/m?K were measured on the trough floor where thick terrigenous turbidites have been deposited. The thermal conductivity of Nankai Trough floor sediments decreases from northeast to southwest along the trough, probably because of the decreased grain size and/or changes in sediment mineral composition. High thermal conductivities (??1.0?W/m?K) were measured in fault scarps on the accretionary prism. A landward increase in these values on the prism may be explained by decreased porosity of the sediments attributable to tectonic deformation during accretionary prism development. At the base of the fault scarp of the frontal thrust, low thermal conductivities (<0.9?W/m?K) were measured, likely reflecting the high porosity of the talus deposits. Low thermal conductivity (0.9?W/m?K) was also measured in slope basins on the accretionary prism, likely also related to the high porosity of the sediments. Our results demonstrate that, for accurate heat flow measurement in an area of varied topography, the geothermal gradient and the thermal conductivity of the sediments must be measured within regions with similar topographic features. 相似文献
17.
Windblown sand control in coastal areas of China began in the 1950s, but was restricted to coastal afforestation 500 to 1000 m landward from the storm-tide line (the maximum height reached by waves during a powerful storm); there were no studies of the supratidal and intertidal areas, where mobile sands create windblown sand damage problems. We therefore studied the formation conditions, characteristics, and damage mechanisms for aeolian sand activity in these areas. Based on the results, we propose suitable sand control measures that combine blocking of the moving sand with stabilization, initially using engineering measures then concluding with biological measures. Control measures include establishing dikes in the intertidal area, erecting nylon nets, and planting Cynodon dactylon behind the dikes on gentle sandy slopes above the high-tide line and below the storm-tide line; spraying sand stabilizer on steep slopes beside moving sand and erecting sand fences on both sides; and spreading mulch nets and mixing clay into the surface, thereby creating a comprehensive protective system that functions as a breakwater, and blocks and stabilizes sand. This protected installations along the beach and improved the ecological environment, leading to the establishment of mangrove seedlings that also stabilized beach areas. These results fill a large gap in the research on controlling windblown sand damage in China's coastal dune areas, and will have significant implications for controlling such areas in other climatic areas. 相似文献
18.
Bioturbated sediments recording distal expressions of paralic depositional environments are increasingly being exploited for hydrocarbons in the super-giant Pembina Field (Cardium Formation), Alberta, Canada. These strata were previously considered unproductive due to limited vertical and horizontal connectivity between permeable beds. In these “tight oil” plays (0.1–10 mD), pressure decay profile permeametry (micropermeability) data indicate that sand-filled burrows provide vertical permeable pathways between bioturbated and parallel-laminated sandstone beds in the central, northeast and northwest parts of the field. This relationship enables the economic exploitation of hydrocarbons via horizontal drilling and multi-stage hydraulic fracturing. As the exploitation of bioturbated strata progresses in the Pembina Field, additional primary targets are being sought out, and horizontal waterflooding is being considered in areas where horizontal wells exist. Proximal to historical produced conventional targets, reservoir analyses indicate that areas where the bioturbated facies average permeability lies between 0.35 mD and 0.85 mD and sandstone isopach thicknesses are between 0.25 m and 2.5 m should be targeted in east-central Pembina.Micropermeability values enable correlation of bulk permeability from plugs and full-diameter samples to the heterogeneous permeability distributions in intensely bioturbated strata. Bulk and micropermeability data are graphically compared, and permeability distributions are mapped across the field. Using isopach thickness of bioturbated facies, production data, and permeability data, “sweet spots” are identified for placement of effective waterfloods.Production information for recently drilled horizontal wells in the Pembina Field demonstrate that bioturbated muddy sandstones and sandy mudstones in paralic environments can be economically exploited when sand-filled burrows provide connectivity between sand beds. However, well performance within these poorly understood unconventional tight oil plays can better be predicted with an in-depth characterization of their facies and complex permeability heterogeneities. Based on our results, it is clear that micropermeability analysis can be effectively employed to differentiate between economic and sub-economic plays, identify areas with high effective permeability, and high-grade areas for enhanced oil recovery schemes. 相似文献
19.
Jackson O. Blanton Harvey Seim Clark Alexander Julie Amft Gail Kineke 《Estuarine, Coastal and Shelf Science》2003,57(5-6):993-1006
This study describes the transport of salt and suspended sediment in a curving reach of a shallow mesotidal coastal plain estuary. Circulation data revealed a subtidal upstream bottom flow during neap tide, indicating the presence of a gravitational circulation mode throughout the channel. During spring tide, landward bottom flow weakened considerably at the upstream end of the channel and changed to seaward in the middle and downstream areas of the reach, suggesting the importance of tidal pumping. Salt flux near-bottom was landward at both ends of the channel during neap tide. At spring, however, the salt flux diverged along the bottom of the thalweg suggesting that tidal pumping caused a transfer of salt vertically and laterally into the intertidal zone. Thus, landward flux of salt is maintained even in the presence of subtidal seaward flow along the bottom at the downstream end of the channel.Landward bottom stress is greater than seaward stress, preferentially transporting suspended sediments upstream. Compared with salt, however, the weight of the suspended sediments causes less upward transfer of sediments into the intertidal zone. Flood flow carried more suspended sediments landward at the upstream end compared with the downstream end. We speculate that secondary flow in the curving channel picks up increasing amounts of suspended sediments along the sides during flood and adds them to the axial flow in the thalweg. Since the landward flow along the bottom of the thalweg weakens and even reverses during spring tide, there appears to be a complex re-circulation system for sediments re-suspended in curving channels that complicates the picture of a net transport of sediments landward. 相似文献
20.
Facies, internal structures and sequences of modern Gironde-derived muds on the Aquitaine inner shelf, France 总被引：1，自引：0，他引：1
Seventy cores from the Aquitaine continental shelf were examined using radiographic and grain-size techniques in order to describe the sedimentary structures of the muddy deposits, and to evaluate their depositional processes. Four lithofacies are identified in this fine-grained deposit: (a) homogeneous silty sand, (b) interbedded homogeneous mud and sand, (c) silty-clayey mud, and (d) mottled mud. They show a logical pattern in relationship to the water depth and the distance from the coast.
Primary structures are present particularly in the landward and central portion of the mud fields, where the sediment is organized into sequences with a sharp-based erosional contact, overlain by a fining-up succession (centimetre to decimetre scale). The beginning of each of these is characteristic of a high-energy storm event, which is common on this shelf. The settling of suspended fine sediment corresponds to the flood estuarine discharge during quiet periods. Primary sedimentary structures decrease in the distal area where the muddy sediment is frequently reworked by infauna. Finally, primary structures and their preservation depend on the relative magnitudes of surface waves, storms, infaunal mixing and fluvial sediment deposition rates (i.e. floods). 相似文献