Continental shelves carbonate deposition

Rao, A. M. P., McCarthgy, M. J., Gardner, W. S., andjahnke, R. (2007). respiration and denitrification in permeable continental shelf deposits on the South Atlantic Bight Rates of Carbon and nitrogen cycling from sediment column experiments. Continental shey Res. 27, 1801—1819. 

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. 

The spring vertical fluxes in ECS continental shelf waters vary by area and water depth (Song, 1997). Vertical carbon transport is mainly in the form of POC. In surface waters, more than 98% of total carbon is transported in the form of POC the munber exceeds 68% in water near the bottom. Fluxes apparently can be influenced by resuspension of the substrate. In ECS continental shelf waters, 98% of carbon is stored as organic carbon, more than 83% as DOC (mean 87.5%) and the rest as POC (mean 11%). Therefore, ECS carbon originates from the exchange of CO2 at the sea-air interface, and DIC becomes DOC and POC through phjdoplankton photosynthesis and zooplankton secondary production. In plankton and depositing particles, particulate... 

Lin S., Huang K.-M. and Chen S.-K. (2000) Organic carbon deposition and its control on iron sulfide formation of the southern East China Sea continental shelf sediments. Cont. Shelf Res. 20, 619-635. 

The Permian Phosphoria Formation in the northwestern Interior United States contains two phosphatic and organic-ncarbon-rich shale members, the Meade Peak Phosphatic Shale Member and the Retort Phosphatic Shale Member. Ihese rocks were formed at the periphery of a foreland basin between the Paleozoic continental margin and the North American cratonic shelf. The concentration, distribution, and coincidence of phosphorite, organic carbon, and many trace elements within these shale members probably were coincident with areas of optimum trophism and biologic productivity related to areas of upwelling. In the Phosphoria sea upwelling is indicated to have occurred by sapropel that was deposited adjacent to shoals near the east flank of the depositional basin. 

The surface runoff from the World s land plays an important role in the global carbon mass exchange. The continental runoff supply of HCO is 2.4 x 10 tons/year, that is, 0.47 x 10 tons/year for carbon. Besides, the stream water contains dissolved organic matter at 6.9 mg/L, which makes up to an annual loss of 0.28 x 10 tons/year. The average carbon concentration of suspended insoluble organic matter in the stream discharge is 5 mg/L, which gives the loss of about 0.2 x 10 tons/year. Most of this mass fails to reach the open ocean and becomes deposited in the shelf and the estuarine delta of rivers. We can see that equal amounts of Cc and Co (0.5 x 10 tons for each) are annually lost from the World s land surface (Dobrovolsky, 1994). 

Early Palaeozoic rocks, 650 to 345 m.y. old, are widely variable in lithofacies, and represent markedly different tectono-strati-graphic depositional environments. They include obducted ophiolitic crustal sequences, volcanic island arc, fore-arc trench and back-arc basin successions, and thick sections of shelf-deposited carbonate and clastic sedimentary rocks. Large volumes of continental subaerial rocks, including arenaceous clastic sedimentary and volcanic rocks, are generally rare and restricted to Cambrian and Devonian strata. 

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