Tidal Lagoon Research Articles

Variations in Littoral Sand Features with Special Reference to Washover Forms on Caminada-Moreau Coast, Louisiana: ABSTRACT

Much documentary evidence (maps, aerial photographs, special surveys) exists by which the historical retreat of the Caminada-Moreau, Louisiana, beach coastline can be measured. Retreat is constantly producing new beach and related landforms. The two main processes are washover and eolian sand movements. Repeated surveys along fixed lines have identified appreciable differences by which sand encroaches on different types of landward surfaces such as marshes, old distributary channels, lakes, tidal lagoons, and manmade features (pipeline canals). Tidal change, wave action, wind strength and direction, and vegetation are the main factors that produce variations in the sand features, but the forms of the preexisting reception surface are also important. Some estimate of the e fect of severe storms or hurricane activity can also be made by correlating climatic records, aerial photographs, and older landforms. Small-scale surface characteristics are produced by rain wash, and lake- and bayou-margin wave effects. Several physiographic situations are repeated along the 19-km-long coastline: wide flat washover beaches, concentrated washover splays, microcliffs in old dunes, active dunes, and stabilized dunes. Some of these differences can be related to the presence or absence of an organic silt (old marsh) platform in the intertidal zone, whereas other features seem to be related to systematic longshore changes operating between Caminada Pass and the Fourchon outlet of Bayou Lafourche. End_of_Article - Last_Page 1609------------

Marine faunal assemblages in the Silurian-Devonian Keyser Limestone of the central Appalachians

Sedimentological analysis of the Keyser Limestone (Upper Silurian - Lower Devonian of the central Appalachians) indicates that its sediments were deposited in a range of marginal and shallow marine environments. Major depositional environments include: tidal flat, lagoon, barrier bar and island, and open marine shelf. Each major environment is represented by a lithofacies which is lithologically and faunally distinct. Tidal flat lithofacies are characterized by eurytopic organisms, including ostracodes, gastropods, stromatoporoids and blue-green algae. Lagoon lithofacies are dominated by bryozoans, brachiopods, ostracodes and stromatoporoids. Barrier lithofacies are characterized by rooted crinoids, encrusting bryozoans and robust brachiopods. Open shelf lithofacies contain a diverse fauna of cystoids, crinoids, bryozoans and brachiopods. The distributions of faunal assemblages in the Keyser show no simple relationship to either water depth or distance from shore. They are, in general, related to the distributions of depositional environments. Recurring associations of brachiopod genera were not found in the Keyser. With few exceptions, any genus may be found in any subtidal environment. Abundance of brachiopods is related to the abundance of local hard substrates (usually bryozoans).

MODEL VERIFICATION FOR TIDAL CONSTITUENTS

Installation and operation of an automated model data acquisition and control system have made it possible to make a quantum advance in the accuracy and time required for verification of tidal inlet (or estuary) hydraulic models. The flexible sampling rate (usually about 200 samples per model tidal cycle for each gage) and digital recording of these data make them ideal for harmonic analysis and comparison with prototype data defining the coefficients and phase for each tidal constituent at various key locations within the tidal lagoon and at an open-ocean station removed from the immediate influence of the tidal inlet. The concept used is to force the model with the M2 tidal constituent with the amplitude being correct at the ocean tide gage. A harmonic analysis is performed at all other gage locations corresponding to the prototype measurements, and the amplitude and phase (relative to the ocean tide gage) are calculated and compared with the prototype data. Investigation of the relative phases between various gages quickly shows those areas where either more or less model roughness is required. It is reasonable to expect to be able to have all phases for the M2 constituent verified within 1 degree. Tidal elevations can almost always be expected to be verified to within a maximum deviation of ;+0.1 ft in both tidal height and mean tide level. Upon verification of the M2 constituent, which practically insures that the proper channel roughness is obtained, a progressive tide can be constructed; and it should be attempted to perform a verification for a 14.765-day (synoptic period for M2 and S2 components) progressive tide at east coast locations using the prototype measurements of tidal velocities for the final verification data. Should additional roughness be necessary, it will almost always be on the mud flats or marsh areas. Computations are made to illustrate the energy transfer from the M2 constituent to higher order harmonics as the wave propagates from the ocean to the back of the estuary, and it is shown that this energy transfer is, at worst, the same order of magnitude in both the model and prototype.

Sediments and Stratigraphic Framework of the Copper River Fan-delta, Alaska

ABSTRACT The Copper River has prograded a marine dominated fan-delta onto the deep, tectonically active northern shelf of the Gulf of Alaska. The morphology and internal stratigraphy of the delta system are products of the sporadic influx of great volumes of bed load sediment into a basin characterized by a high wave, tide, and current energy flux. Subaerial morphology and processes of the delta are typical of humid region alluvial fans. The fan margin is, however, completely reworked and modified by wave and tidal action, and marine portions are skewed westward by longstore drift and marine currents. Major environments of the delta include (1) the subaerial deltaic plain, consisting of marsh and swamp organic muds, and braided to estuarine distributary channel fills; (2) the tidal lagoon, composed of tidal sand and mud flat sequences interlaced with a complex of tidal channel fills; and (3) the shoreface, which consists of marginal island, breaker bar, and middle shore face sands, lower shoreface sand and mud, and prodelta/shelf mud. Marine influenced tidal lagoon and shoreface facies are volumetrically dominant components of the system. The Copper River fan-delta is a working depositional model for tectonic clastic wedges prograded into an open marine basin.

The epibionts of Sargassum muticum in British waters

This study was initiated by suggestions that the Japanese brown alga Sargassum muticum (Yendo) Fensholt, recently found to be invading shores along the eastern Solent (Southern England), might replace certain common native plants, to the possible detriment of local epibiont communities. Eighty animal, 52 plant and 9 fungal species have been identified from S. muticum plants collected at four different localities. Animal fouling was most conspicuous on permanently submerged plants growing along the edge of floating harbour installations. Algal epibionts were most numerous and varied on S. muticum from tidal lagoons on a well-scoured but sheltered rocky shore. Most of the epibionts colonised the perennial portions of the plants, close to the holdfast. A few settled along the fronds in summer, but none were found in the region of the secondary and tertiary apical meristems. Seasonal variations in the abundance and diversity of algal epibionts were observed; most were restricted to summer, but winter and all-year-round species were also noted. Fungal studies on S. muticum have isolated only saprophytic species, which are also common locally on other Phaeophyceae. Overall, these data suggest that S. muticum can support a considerable epibiota and, therefore, its introduction seems unlikely to result in a significant change in local epiphyte communities.

Observed beach modifications, Kiloran Bay, Isle of Colonsay, Argyll

Synopsis Observation of marked changes in beach configuration occurring over a short time period was possible during July and August 1971 at Kiloran Bay, Isle of Colonsay, Argyll. A semi-permanent lagoon situated behind a beach bar of calcareous sand, having survived periods of both neap and spring tides accompanied by offshore winds, was transformed to a tidal lagoon by the events of a single spring flood tide accompanied by a strong onshore wind. The tidal lagoon survived for only three days, being eliminated in the course of shoreward migration of the beach bar by the action of large waves resulting from Atlantic swell.

A GEOMICROBIOLOGIGAL STUDY OF THE PRE-CAMBRIAN NONESUCH SHALE

Summary The paper describes the organic content of specimens representing some part of the Nonesuch Shale of Upper Keweenawan age (1,075 ± 50 million years) forming part of the Copper Belt on the southern flanks of the Lake Superior Basin in Ontonagon County, Michigan. The remarkably well preserved organic matter has been studied optically in thin section, by acid maceration analysis, and separately, in ultrathin section of isolated organic matter, by electron microscopy. The amorphous organic groundmass consists of saprophytic microbiological degradation products which include spore-like bodies or “sporomorphs” (acritarchs) in various stages of degradation, with attacking microorganisms often in situ. The further microorganism content resembles morphologically bacteria, actinomycetes or fungi and the total organic content represents an ecosystem. The remarkable mattes of tissue composed of larger fungi are predominantly oriented with the bedding on the organic-rich elements of paired, laminated or varved deposits. The remains constitute an assemblage which recalls that of Moore (1964a) in which forms such as Anthracomyces cannellensis , Palynomorphites and “ Phellomyces ” were shown to be instrumental in organic degradation. This process now demonstrated from a Pre-Cambrian environment is one with an antiquity of at least a thousand million years and suggests that conditions with regard to physico-chemical-biological constitution and related environmental parameters have been comparable over this time period. The paper supports the general sedimentological conclusions of White and Wright (1954) concerning the depositional environment but deduces a tidal lagoon or mud flat environment of Pre-Cambrian age. The organic assemblage, the biological process of degradation and the characteristics of the sedimentary environment are compared with known geological and recent examples of laminated or varved, lacustrine; tidal lagoon and mud flat environments. Reference is made to the geochemical characteristics of some of these related sediments in an attempt to reach a more pertinent assessment of the Pre-Cambrian environment, and of the periodicity of events which the Nonesuch sediments display.

Stratigraphic Analysis Through Determination of Depositional Environments: ABSTRACT

The Mesaverde Formation of the Western Interior Cretaceous seaway includes rock units representative of off-beach, beach, lagoon, swamp, and floodplain environments of deposition. Because of migration of the shoreline by transgression and regression, the sedimentary products of various environments are arranged vertically in the geologic record in the same succession as they occurred laterally at the time of deposition. The detailed distribution of the potential reservoir beach sandstone bodies in a regressive sequence follows different patterns, depending on variations in the relative rate of submergence during progradation. These variations are reflected in the character of the back-beach environment. A mainland beach-floodplain progradation, reflecting a low rate of su mergence, results in a tabular sheet of beach sandstone which intertongues only slightly with the overlying floodplain End_Page 2036------------------------------ rocks; a barrier island-lagoonal progradation, reflecting a high rate of submergence, comprises a series of discrete sandstone lenses arranged en echelon, each lens intercalating landward with lagoonal deposits and seaward with off-beach marine shale. During transgression, because of the step-like topography of a barrier island-lagoonal terrain, shoreline sandstone bodies are developed only discontinuously, giving rise to asymmetrical cycles. Because of the general paucity of organic remains in the Mesaverde, the determination of depositional environments commonly must be accomplished by the evaluation of stratification. Though there are no single stratification features peculiar to particular environments, sequences of stratification may be diagnostic. Stratification in rocks occurs in response to physical-depositional processes; the vertical sequence of stratification in a regressive suite of rocks reflects the lateral distribution of processes operative at the time of deposition. Beach stratification, from bottom to top, includes laminae deposited in the transition zone between off-beach shale and offshore beach sandstone, the submarine bar zone, the fore-shore beach, and the back-shore beach. A vertical sequence of lag on stratification may reflect deposition in a tidal delta, lagoon pond, tidal channel, wave flat, and salt marsh. The character of the stratification in the different sub-environments may be determined by study of modern environments and processes; the great variety of processes present within these modern environments yields perspective on the variety of stratification to be expected in the geologic record. End_of_Article - Last_Page 2037------------

An adaptive correlator for underwater measurements. : Wolf, Alfred A. and J. H. Dietz 1962. Marine Instrumentation, Inst. Soc. Amer. Plenum Press, N.Y. 1: 347–354.

Marine foundation organisms such as seagrasses, corals, and kelps facilitate the distribution of numerous organisms by creating refuges from environmental stressors and by providing food and substrate for settlement and growth. Barren soft-sediment systems often have faunal organisms that facilitate other species by habitat modification. We investigated how an abundant (21 m−2) tube cap forming polychaete, Diopatra cuprea, facilitates macroalgal distribution in Hog Island Bay, a turbid shallow tidal lagoon in Virginia (USA). Seventy percent of the number of mudflat macroalgae were found incorporated into protruding D. cuprea tube caps and field experiments showed that D. cuprea facilitates algal persistence by providing a stable substrate retaining algae against hydrodynamic forces such as tidal flushing and storm surge. If tube caps were removed, simulating storm-induced erosion, they were rebuilt within days and new drift algae incorporated. Also, D. cuprea facilitated the algal assemblage by fragmenting thalli in the attachment process, thereby ensuring a constant fragment supply for vegetative re-growth if storm-induced pruning occurs. On a species-specific level, Gracilaria verrucosa and Ulva curvata benefited more from tube cap construction compared to Fucus vesiculosus, Agardhiella subulata and the alien Codium fragile ssp. tomentosoides. This was partly because G. verrucosa and U. curvata were incorporated and fragmented more readily, and partly because they probably have physiological, morphological and biomechanical traits that enable them to better co-exist with D. cuprea. These results suggest that macroalgal distribution throughout Hog Island Bay to a large extent is linked to the distribution of D. cuprea. The processes of algal attachment, retainment, recovery, re-growth and fragmentation, can have important ecosystem implications because of the sheer abundance of the Diopatra-Gracilaria/Ulva association.

Tidal Action as a Cause of Clay Accumulation

ABSTRACT The tidal flats on the southeastern border of the North Sea are developed behind a chain of barrier islands. In this area the grain size of the sand decreases from the inlets towards the inner shores and the tidal watersheds behind the islands. Likewise the clay content increases, so that muddy sands and even sandy muds are formed. This condition is explained by the action of tidal currents combining with other, mainly biological phenomena. Pellets and flakes are formed and these are carried inwards in consequence of the settling lag effect and the scour lag effect. In estuaries and tidal lagoons similar conditions may be responsible for lateral changes in clay content. In ancient basins such lateral increase in fine grained material may indicate approach to the mainland shore and increasing distance from passes between sandy barrier islands. This study is an elaboration of suggestions offered by Postma (1954). A more detailed account with extended bibliography and frill acknowledgements has been given in an earlier paper (van Straaten and Kuenen, 1957).

Reconnaissance Observations on Geology of Trinity Islands, Alaska: ABSTRACT

The Trinity Islands, Tugidak on the west and Sitkinak on the east, form the southwesterly extent of the Kodiak Islands group. Each island is approximately 5 miles wide by 20 miles long. The surface of Tugidak Island is a series of low wave-cut terraces maximum elevation 200 feet. Sitkinak Island comprises a group of hills on the east and west, maximum elevation 1,640 feet, separated by a valley enclosing Sitkinak tidal lagoon. The bedrock of East Sitkinak Island is Cretaceous (?) marine epineritic bedded graywacke and siltstone complexly folded and faulted. West Sitkinak Island is Cretaceous (?) marine infraneritic thin-bedded siltstone and fine graywacke isoclinally folded and faulted. The thickness of these units is unknown; structural trends are northwest. Sitkinak lagoon and valley lie in a northwest-trending graben in which about 4,000 feet of Eocene (?) continental to brackish marine conglomerate, sand, silt, and coal crop out. The bedrock of Tugidak Island consists of Plio-Pleistocene soft mudstone and thick-bedded gray sands, which strike N. 45° E. and dip 5° NW. The Cretaceous sediments were deposited in a northeast-trending mobile, extra-continental, geosyncline and were probably derived from a volcanic landmass on the southeast. Late Cretaceous or Laramide diastrophism brought to a close the Cretaceous sedimentation cycle. The Tertiary sediments were deposited in a similar less well developed geosyncline but had a northwesterly source. Intermittent orogenic uplift near the close of this cycle caused non-deposition or erosion of mid-Tertiary sediments. Late Tertiary diastrophism that closed the Tertiary cycle of sedimentation has continued to Recent time and includes differential orogenic movements, in part along major northeast-trending faults. End_of_Article - Last_Page 354------------

THE HISTORY OF A TIDAL LAGOON INLET AND ITS IMPROVEMENT (THE CASE OF AVEIRO, PORTUGAL)

The described case history is known since the Xth century, and on a scientific level since the end of XVIIIth. Origin and free evolution of the inlet up to 1800, as well as results obtained by artificial improvement attempts subsequently undertaken, are analysed, in order to investigate the main features of local physiography and the way it reacts to human interventions intended to meet ever-increasing navigation requirements. The remarkable success of the projects undertaken, especially of that being executed, seems to legitimate the inference of some principles of general interest as long as tidal lagoon inlets improvement is concerned. Stress is laid upon difference from principles valid in estuaries' amelioration.

Notes on Snakes Collected in Liberia

THE west African Republic of Liberia has an area of approximately 43,000 square miles. It lies between 4? 22' to 8? 50' north latitude, and 7? 33' to 11? 32' longitude west of Greenwich, and has one of the most humid and rainiest climates of Africa. Most of the country is covered by hills of varying heights. A mixed forest is the predominant vegetation of the hinterland. The typical vegetation of the coastal belt, however, is open grassland with patches of bracken fern (Pteridium acquilinum) and trees of the monkey plum (Parinarium macrophyllum). This belt is flat and characterized by creeks and tidal lagoons which are fringed with mangrove trees (Rhizophora mucronata). While stationed in Liberia (1943-1945) I had the opportunity to study the herpetology of various parts of the country. Notes on the species of snakes collected follow:

Areal Variation of Organic Carbon Content of Barataria Bay Sediments, Louisiana

Bottom sediments were collected from part of Barataria Bay, a tidal lagoon on the Mississippi delta. The organic carbon content of the samples was determined by a dry combustion method. The analytical data were used to prepare a map of the areal distribution of organic carbon in the environment. These data are correlated with the size attributes of the sediments; in general, the finest sediments have the largest content of organic carbon. The relation between average size and organic carbon appears to be exponential. The data are related to recent work on shoestring oil sands. The pattern of sediments in Barataria Bay supports earlier work by providing a suitable areal variation for the origin of the oil in the finer sediments, and its accumulation in the coarser sediments of the same general environment, by means of channels which serve as natural conduits for migration.

A Theory of Evolution of Lagoon Deposits on Shorelines of Emergence

The tidal delta at Barnegat Inlet and deposits at other New Jersey inlets shown on coast charts suggest an orderly evolution of deposits in tidal lagoons on young shorelines of emergence. In an effort to deduce this evolution from the factors governing tidal inlets, hypotheses are presented according to the following sets of assumed conditions: (1) the inlets open simultaneously and remain stationary; (2) the inlets open successively and remain stationary; (3) the inlets open simultaneously and migrate rapidly; and (4) the inlets open successively and migrate rapidly. Each hypothesis is presented in a series of five stages of development of the same part of the same shoreline, but it is believed that the different stages all may exist on different parts of the same shoreline at the same time. The theory is tested by comparison of the idealized stages of development with coast charts of New Jersey and Long Island. Both shores exhibit features corresponding to the deductions, New Jersey features indicating ...

Characteristics of continental clastics and chemical deposits

Introduction Broadly considered, the continental sediments are all those which have been deposited elsewhere than in the sea. By this definition we must include among them not only the deposits made by rivers and other agencies working on the land, but also the sediments laid down in lakes and marshes. Between marine and continental types there is, of course, no sharp line of demarkation, but a transition zone occupied by the deposits made in estuaries, tidal lagoons, and sounds, on beaches, deltas, etcetera. It would be gratifying if we could establish a few simple rules for distinguishing between marine and continental deposits; but with certain exceptions this is impracticable. There are but few satisfactory criteria of general application for separating continental from marine sediments. In the past reliance has often been placed on the fossils; but in the continental sediments fossils are generally wanting, and not uncommonly they are rare even . . .