Sediment sorting

Figure 4. Sketch of distribution of seabed sediment sorting coefficient (Qdcp).

Poorly sorted sediments comprise very different particle sizes, resulting in a dense rock fabric wifh low porosify. As a resulf the connate water saturation is high, leaving little space for the storage of hydrocarbons. Conversely, a very well sorted sediment will have a large volume of space between the evenly sized components, a lower connate water saturation and hence a larger capacity to store hydrocarbons. Connate water is the water which remains in the pore space after the entry of hydrocarbons. 

Shelf (elastics) Sheet-like sandbodies resulting from storms or transgression. Usually thin but very continuous sands, well sorted and coarse between marine clays. Very high productivity but high quality sands may act as thief zones during water or gas injection. Action of sediment burrowing organisms may impact on reservoir quality. 

Loess is a well-sorted, usually calcareous, non-stratified, yellowish-grey, aeolian clastic sediment. It consists predominantly of silt-sized particles (2-50 mm), and contains normally less than 20 percent clay and less than 15 percent sand. It covers the land surface as a blanket, which is less than 8 meters thick in the Netherlands (exceptionally 17 meters) but can reach up to 40 meters in Eastern Europe and 330 meters in China. 

Ice rafting is responsible for 7% of the terrigenous input of siliclastic particles to the ocean. When the ice melts, the particles settle to the seafloor to form glacial marine deposits. These are currently forming at latitudes greater than 40°N and 50° S. Most of the glacial marine sediments are poorly sorted deposits composed of relatively unweathered materials with chlorite being the dominant clay mineral. In the North Atlantic, layers... 

Unsorted sediments Sediments that contain unconsolidated grains exhibiting a wide range of particle sizes. Same as poorly sorted sediments. 

Well-sorted sediments Sediments composed of one size class of particles, e.g., a deep-sea clay. 

The detrital material is most frequently semi rounded and well sorted. It is rather loosely arranged in the arenites - the indicator of grain contacts in the sediment may be estimated at about 2.0. Point contacts are few, or absent in the wackes. 

One aspect of sedimentary 7 8 chlorite formation which is particularly interesting is the fact that these minerals are never found forming at depths greater than 80 meters in recent sediments. Porrenga (1967b) thinks that they are characteristic of tropical sediments and their formation is thus temperature dependent. This appears invalid since they are known to form in recent sediments in a Scottish loch (Rohrlich, e al.. 1969). Nevertheless there does seem to be a bathymetric control on their occurrence. This is probably not a pressure effect but more likely some sort of factor related to organic activity in the sediments which is controlled by the biotic factors of sea depth, temperature, nutrients, etc. 

Sedimentation runs should be conducted at a constant temperature, not only so that Ap and T7 are known, but also to minimize disturbances due to convection. Any sort of disturbance will obviously disrupt the segregation of the particles by size that has occurred as a result of sedimentation. An intrinsic difficulty with the balance method lies in the fact that the liquid below the balance pan is less dense than the liquid with dispersed particles above the pan. Thus, there is a tendency for a counterflow of pure solvent to arise, which would introduce an error in the particle size analysis. 

Contours like this are qualitatively the same sort of thing we obtain from sedimentation-diffusion experiments as shown in Figure 2.9. Therefore let us consider the relationship between the two types of data. In general, exactly the same factors affect both the intrinsic viscosity and the friction factor ratio, but the functional dependencies are somewhat different. Figure 4.13b shows how a contour of f/f0 selected from a sedimentation-diffusion study and an intrinsic viscosity contour selected on the basis of viscosity experiments might overlap. In this case the solvation-ellipticity combination is characterized unambiguously a/b = 2.5 and (ml b/m2) = 1.0. Figure 4.13b shows the complementarity of viscosity and sedimentation-diffusion data. 

Now we want to apply the box model approach to a two-box system which consists of a completely mixed water body in contact with a sediment box. Although the sediment column can hardly be visualized as being completely mixed, the concept of a surface mixed sediment layer (SMSL) introduced in the previous section is an approximate view of the sediments as mixed box. In fact, for strongly sorbing chemicals the diffusive penetration into the sediment column is so slow and the storage capacity of the top 1 to 2 cm so large, that the deeper parts of the sediments can be treated as sort of a permanent sink from which no feedback to the SMSL and to the open water column is possible. 

Sorting the terms in the usual manner yields the dynamic equation of the total lake concentration, Ctop. Note that the equation is now coupled with the sediment concentration Cssc. 

Tuchia which has frequent use in the transmutation of metals, is an artificial and not a natural mixture, for tuchia is made from the smoke which rises and is solidified by adhering to hard bodies, when brass is purified from the stones (minerals) and tin which are in it. But the best kind is from that which is sublimed from that (that is, resublimed), and then that which in such sublimation remains at the bottom is climia,62 which is called by some succudus. There are many kinds of tuchia, as it occurs white, yellow and turning toward red. When tuchia is Washed there remains in the bottom a sort of black sediment of tuchia. This is something called by some Tuchia Irida. But the difference between succudus and tuchia is as we have stated, namely, because tuchia is sublimed and succudus is what remains at the bottom unsublimed. The best is volatile and white, then the yellow, and then the red the fresh is considered better than old. All tuchia is cold and dry and that which is washed is considered better in those operations68 (that is, in above mentioned transmutation of the metals). ... 

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