Tidal flats

L G-Gn, platy, finely micaceous calcareous slightly fossiliferous shale (tidal flat)... 

Low salinity exemplified by freshwater and seawater that are mixed near the estuary of a river flowing into the sea. Tidal flats and lagoons of low salinity are also considered as brackish areas (PIANC, 2000). Volume 2(9). 

Mg-rich chlorites do not seem to form readily in low-temperature marine environments. Mixed-layer chlorite-vermiculites form fairly easily in magnesium-rich environments but complete development of the brucite sheets must be considerably more difficult. Mixed-layer chlorite-vermiculite is the predominant clay in the Lower Ordovidian limestones and dolomites of southern United States, usually over a thousand feet thick and extending over 500,000 square miles, yet very little chlorite is present (Weaver, 1961a). These mixed-layer clays and others like them appear to have formed on extensive tidal flats where the clays were exposed to alternating evaporitic... 

These clays occur in limestones, dolomites, evaporites, shales, siltstones, and hydrothermal deposits. All the sedimentary material appears to have a diagenetic origin. Although the physical environments vary, the chemical environments should be similar. Saline or even super-saline conditions are implied by the presence of evaporite minerals associated with some of the deposits. In the other deposits it is possible that temporary evaporitic conditions (e.g., tidal flats) existed long enough for brucite to precipitate between the layers of expanded-layer minerals. It appears plausible that the parent material was a montmorillonite-like mineral (probably detrital in most cases). 

The tidal flats of marine environments are areas of extreme complexity and biological activity. They serve as both sources and sinks of a wide variety of compounds and materials. They are in a constant state of mass, energy and momentum flux with the surrounding environment In these areas sulfur plays a major role in biological processes, principally because of the relatively nigh concentration of sulfate ion in marine waters. 

Anoxyphotobacteria live in the anaerobic zones of waters, where they are sufficiently provided with sulfide and light. Typical habitats are salt marshes, lakes, sewage and coastal lagoons, hot springs, salt and soda lakes and the so-called "Farbstreifensandwatt" (versicolored, sandy tidal flat) (see l-2a). 

The magnitude of the artifact is such that coastal and wetland data in the literature is not likely to be seriously affected. An example of this is our Bahamas data ( ) which illustrates the dominance of local island sources elevated concentrations were preceded by wind shifts bringing air from the island of Andros which has extensive tidal flats. Similarly, the H2S concentrations measured on the Gulf of Mexico cruise in the same paper most likely reflect the advection of continental and tidally derived HiS. Brief periods of low H2S concentrations (< 10 ppt) were obtained in the Gulf Stream near the end of both of these cruises during brief exposure to easterly open ocean air. 

A typical barrier-island system can be divided into three depositional environments (barrier beach, lagoonal/bay, and tidal channel -delta complex) each of which contains a number of smaller subenvironments (2). This work focused on a typical bay-fill sequence in which bay sediments are overlain by tidal flat deposits... 

Megascopic and microscopic analyses of the sediments provided the information for the correlated stratigraphic columns presented in Figure 3. Marsh, tidal flat, and bay sediments were discerned from each of the three cores. These sediments were differentiated on the basis of grain size, fossil content, and the relative abundance of Spartina root and rhizome debris. 

Iron monosulfides show an antithetic relationship with pyritic sulfur (Table I). The highest amounts of acid volatile sulfides (which remained small compared to S in pyrite) occur directly beneath the marsh sediments within the upper portions of the tidal flat deposits. The high value for iron monosulfides in the upper part of the tidal creek sediments may be related to high rates of sulfate reduction at these depths. 

The superposition of marsh sediments on older bay and tidal flat sediments has likely increased their pyrite content. Environmental overprinting has been reported in both recent sediments (16) and in the rock record (17). 

Eutrophication Processes in Coastal Systems Origin and Succession of Plankton Blooms and Effects on Secondary Production in Gulf Coast Estuaries, Robert J. Livingston Handbook of Marine Mineral Deposits, David S. Cronan Handbook for Restoring Tidal Wetlands, Joy B. Zedler Intertidal Deposits River Mouths, Tidal Flats, and Coastal Lagoons, Doeke Eisma... 

Reaves (1986) described another study specifically aimed at relating calcium carbonate preservation to chemical diagenesis in sediments. He compared Mercinaria shells and pore water chemistry in intertidal mud flat and tidal creek... 

Benthic macroalgae and microphytobenthos are important sources of primary production in estuaries and have significant effects on the seagrass, tidal flat, and intertidal marsh habitats. 

Similar to C02, emission rates of CH4 are highly variable in estuaries with the higher rates being found in tidal flat and marsh environments. 

Lucas, C.H., Widdows, 1, and Wall, L. (2003) Relating spatial and temporal variability in sediment chlorophyll a and carbohydrate distribution with erodability of a tidal flat. Estuaries 26, 885-893. 

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