Sedimentation Continental, Shallow Marine

A wide variety of zeolites are known to form in saline lakes where the species present is dependent upon the chemistry of the solutions. Rapid zeolite formation is aided by the existence of the volcanic glass and high water salinities. Potassium feldspar occurs with the common alkali zeolites (Hay and Moiola, 1963 Hay, 1964 Hay, 1966 Sheppard and Gude, 1969, 1971), however, albite is not evident as a diagenetic mineral in saline lakes. 

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Denitrification is a major pathway of carbon degradation in sediments of shallow-marine continental margin areas. Why is it so important for biogeochemical element cycles in the ocean, particularly in terms of regulation of nutrient levels and primary productivity ... 

In hot arid areas where the continental shelf meets the land, marine sabkha-type environments exist. For example, on theTrucial coast ofAbu Dhabi shallow marine carbonate sediments are reworked and bound by microbial mats. In the upper intertidal zone these mats... 

The Cu concentration of crustal rocks (32 34 p,g g ) is approximately equivalent to that for average soils (25 4 p,g g ). However, as the earth material is weathered and transported to streams-lakes-shallow marine sediments there is a minimal enrichment in Cu concentration (39 = 34 = 43 p,gg ) (Table 4). And, as for Pb-Zn-Cd, riverine particulate matter is greatly enriched (100p,gg ) relative to the other sedimentary materials. While the Pb-Zn-Cd concentrations of deep-sea clay are enriched 1.5 times that of the continental sedimentary materials, Cu is enriched approximately five times. The substantial enrichment of Cu in oceanic pelagic clay relative to terrestrial earth materials is due to the presence of ubiquitous quantities of ferromanganese oxides in surficial ocean sediments (Drever, 1988). 

It is convenient to divide the deposition of carbonates in marine sediments into those being deposited in shallow (shoal) water (water depths of a few hundred meters or less) and those being deposited in deep sea sediments, where the water depth is on the order of kilometers. The primary reasons for this division are the differing sources, dominant mineralogies, and accumulation processes operative in these environments. Shoal water carbonates are the topic of Chapter 5. Naturally, there are "grey" areas of intermediate characteristics between these two extremes, such as continental slopes and the flanks of carbonate banks and atolls. 

Pore-water nitrate profiles in marine sediments typically show one of three profile shapes. In sediment with rapid rates of organic matter oxidation relative to rates of solute supply from the overlying water, both oxygen and nitrate concentrations decrease more or less exponentially from overlying water concentrations at the sediment—water interface to zero, with oxygen depletion preceding or simultaneous with nitrate depletion at shallow sediment depth (see 105 m and 440 m profiles in Fig. 6.12). These types of profiles are common in continental shelf and upper slope sediments, and are due to relatively large carbon rain to the sediments (relatively... 

This section primarily focuses on the description of the deposition and accumulation of carbonates in shallow waters and in the deep ocean. The main depocenters for calcium carbonates are the continental shelf areas, as well as island arcs or atolls, which are the typical shallow water environments for massive carbonate formation, and the pelagic deep-sea sediments above the calcite compensation depth catching the rain of small calcareous tests formed by marine plankton in the surface waters. 

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