Sediment deep sea

Terrigenous sediments, i.e. elastics consisting of material eroded from the land surface, are not only understood as nearshore shallow-water deposits on the shelf seas, but also comprise the deltaic foreset beds of continental margins, slump deposits at continental slopes produced by gravity transport, and the terrigenous-detrital shelf sediments redistributed into the deep sea by the activity of debris flows and turbidity currents. 

It needs to be stated in this context, that, in order to compare the quantitative reports of published grain sizes, the international literature does not draw the line between silt and clay at 0.0039 mm - as the U S standard and the Udden-Wentworth scale does (Table 1.3), or the French AFNOR-norm, but sets the limit at 0.002 mm, a value very often found in German literatnre and complying with the DlN-standards. To add to further diversity, modern pnblications from Russia mark the silt-clay transition at a grain size of 0.01 mm (e.g. Lisitzin 1996). 

The sediments in the deep sea consist of only few basic types which in their manifold combinations are suited for the description of a varied facial pattern (Table 1.4). The characteristic pelagic deep-sea sediment far from coastal areas is deep-sea red clay, an extremely fine-grained (median 1 pm) red-brown clay sediment which covers the oceanic deep-sea basins below the Calcite Compensation Depth (CCD). More than 90 % is composed of clay minerals, other hydrogenous minerals, like zeolite, iron-manganese precipitates and volcanic debris. Snch sediment composition demonstrates an anthigenic origin. The 

The hemipelagic sediments are basically made of the same components as the deep-sea red clay 

Most deep-sea sediments can be described according to their composition or origin as a three-component system consisting of 

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When the sample is a solid, a separation of the analyte and interferent by sublimation may be possible. The sample is heated at a temperature and pressure below its triple point where the solid vaporizes without passing through the liquid state. The vapor is then condensed to recover the purified solid. A good example of the use of sublimation is in the isolation of amino acids from fossil mohusk shells and deep-sea sediments. ... 

Global uranium flux calculations have typically been based on the following two assumptions (a) riverine-end member concentrations of dissolved uranium are relatively constant, and (b) no significant input or removal of uranium occurs in coastal environments. Other sources of uranium to the ocean may include mantle emanations, diffusion through pore waters of deep-sea sediments, leaching of river-borne sediments by seawater," and remobilization through reduction of a Fe-Mn carrier phase. However, there is still considerable debate... 

Joly observed elevated "Ra activities in deep-sea sediments that he attributed to water column scavenging and removal processes. This hypothesis was later challenged with the hrst seawater °Th measurements (parent of "Ra), and these new results conhrmed that radium was instead actively migrating across the marine sediment-water interface. This seabed source stimulated much activity to use radium as a tracer for ocean circulation. Unfortunately, the utility of Ra as a deep ocean circulation tracer never came to full fruition as biological cycling has been repeatedly shown to have a strong and unpredictable effect on the vertical distribution of this isotope. 

Additional model studies are needed to explore the effects of CaCOa compensation. Examination of the extent of the CaCOa preservation in deep-sea sediments is needed to verify model predictions of how the [COa] ion content of deep-sea water has changed with time. 

Carbon dioxide is produced as a result of metabolism of all heterotrophic organisms. The concentrations of CO2 in pore water of reduced sediments are therefore high. Autotrophic microorganisms consume CO2 in the oxidized part of the sediment, which can vary in depth from a meter in deep sea sediments to a few mm... 

Lynn, D. C. and Bonatti, E. (1965). Mobility of manganese in diagenesis of deep-sea sediments. Marine Geol. 3,457-474. 

Cochran JK, Krishnaswami S (1980) Radium, thorium, uranium and °Pb in deep-sea sediments and sediment pore waters from the north equatorial Pacific. Am J Sci 280 849-889 Cochran JK, Masque P (2003) Short-lived U/Th-series radionuchdes in the ocean tracers for scavenging rates, export fluxes and particle dynamics. Rev Mineral Geochem 52 461-492 Colley S, Thomson J, Newton PP (1995) Detailed °Th, Th and °Pb fluxes recorded by the 1989/90 BQFS sediment trap time-series at 48°N, 20°W. Deep-Sea Res 42(6) 833-848... 

Dymond J, Suess E, Lyle M (1992) Barium in deep-sea sediment A geochemical proxy for paleoproductivity. Paleoceanography 7(2) 163-181... 

Francois R, Bacon MP, Suman DO (1990) Thorium 230 profiling in deep-sea sediments high resolntion records of flux and dissolution of carbonate in the equatorial Atlantic during the last 24,000 years. Paleoceanography 5(5) 761-787... 

Simpson HJ, Trier RM, Toggweiler JR, Mathieu G, Deck BL, Olsen CR, Hammond DE, Fuller C, Ku TL (1982) Radionuclides in Mono Lake, California. Science 216 512-514 Smith CR, Berelson W, Demaster DJ, Dobbs FC, Hammond D, Hoover DJ, Pope RH, Stephens M (1997) Latitudinal variations in benthic processes in the abyssal equatorial Pacific control by biogenic particle flux. Deep-Sea Res Part II-Topical Studies in Oceanography 44(9-10) 2295 Smith CR, Pope RH, Demaster DJ, Magaard L (1993) Age-dependent mixing of deep-sea sediments. Geochim Cosmochim Acta 57(7) 1473-1488... 

Bertine KK, Chan LH, Turekian KK (1970) Uranium determinations in deep-sea sediments and natural waters using fission tracks. Geochim Cosmochim Acta 34 641-648 Bhat SG, Krishnaswami S, Lai D, Rama, Moore WS (1969) " Th/ U ratios in the ocean. Earth Planet Sci Lett 5 483-491... 

Joly J (1908) On the radium content of deep-sea sediments. Phil Mag 16 190... 

The application of the decay chain to the dating of deep sea sediments was by Piggott and Urry in 1942 using the Ionium method of dating. Actually they measured a (itself through Rn) assuming secular equilibrium had been established between... 

B. R. T. Simoneit, Diterpenoid compounds and other lipids in deep sea sediments and their geochemical significance, Geochim. Cosmochim. Acta, 41, 463 476(1977). 

Bertine et al. [99] have discussed the determination of uranium in deep sea sediments and water utilising the fission track technique. In this technique a weighed aliquot (50-100 mg) of the powdered sample is made into a pel-... 

In this article we plan to focus on two aspects (i) the transport of radionuclides to the ocean floor and the processes which govern their distribution in deep-sea sediments and (ii) the application of deep-sea sediments to retrieve historical records of large scale phenomena, e.g. long term changes in the rate of production of nuclides by cosmic rays. Even while discussing these aspects, our emphasis will be mainly on the processes rather than on the details of the chronometric method. 

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