Alluvial

For example, the many deepwater fields located in the Gulf of Mexico are of Tertiary age and are comprised of complex sand bodies which were deposited in a deepwater turbidite sequence. The BP Prudhoe Bay sandstone reservoir in Alaska is of Triassic/ Cretaceous age and was deposited by a large shallow water fluvial-alluvial fan delta system. The Saudi Arabian Ghawar limestone reservoir is of Jurassic age and was deposited in a warm, shallow marine sea. Although these reservoirs were deposited in very different depositional environments they all contain producible accumulations of hydrocarbons, though the fraction of recoverable oil varies. In fact, these three fields are some of the largest in the world, containing over 12 billion barrels of oil each ... 

Platinum occurs native, accompanied by small quantities of iridium, osmium, palladium, ruthenium, and rhodium, all belonging to the same group of metals. These are found in the alluvial deposits of the Ural mountains, of Columbia, and of certain western American states. Sperrylite, occurring with the nickel-bearing deposits of Sudbury, Ontario, is the source of a considerable amount of metal. 

Iridium occurs uncombined in nature with platinum and other metals of this family in alluvial deposits. It is recovered as a by-product from the nickel mining industry. 

Occurrence. Niobium and tantalum usually occur together. Niobium never occurs as the metal, ie, ia the free state. Sometimes it occurs as a hydroxide, siUcate, or borate most often it is combiaed with oxygen and another metal, forming a niobate or tantalate ia which the niobium and tantalum isomorphously replace one another with Htde change ia physical properties except density. Ore concentrations of niobium usually occur as carbonatites and are associated with tantalum ia pegmatites and alluvial deposits. Principal niobium-beariag minerals can be divided iato two groups, the titano- and tantalo-niobates. 

Continental Shelf. A variety of terms may be appHed to deposits in the continental shelf (conshelf) including beach, bank, alluvial, strand-line, heavy mineral, or placet. These contain mostly industrial materials, mineral sands, or precious metals (Table 1). 

Diamonds were first discovered in ancient times in India and Borneo and later in Brazil in 1670 in alluvial deposits where water had sorted minerals on the basis of density and toughness. This type of tumbling often concentrates the better quality crystals such as those found in the ocean off the west coast of Africa. Exploration can be done by stream panning or drilling in conjunction with a search for the heavy mineral assemblages that accompany diamond. Alluvial deposits account for about 40% of the diamond found in primary sources. 

Alluvial soil formed of a number of layers of non-uniform non-homogeneous soil of different stratifications... 

Although estimates of their abundances vary considerably, Pd and Pt (approximately 0.015 and 0.01 ppm respectively) are much rarer than Ni. They are generally associated with the other platinum metals and occur either native in placer (i.e. alluvial) deposits or as sulfides or arsenides in Ni, Cu and Fe sulfide ores. Until the 1820s all platinum metals came from South America, but in 1819 the first of a series of rich placer deposits which were to make Russia the chief source of the metals for the next century, was discovered in the Urals. More recently however, the copper-nickel ores in South Africa and Russia (where the Noril sk-Talnakh deposits are well inside the Arctic Circle) have become the major sources, supplemented by supplies from Sudbury. 

Schwemm-land, n. alluvial land, -stein, m. a kind of porous brick made from clay and gravel, porous concrete block pumice stone, -verfahren, n. flotation process, -wasser, n. wash water flushing water. 

Biological effects and stimulation of plant growth induced by hydrogel additives are observed at doses which are often much lower than those obtained from purely physical evaluation. For example, it has been recently shown [13] that, according to various criteria of plant development, the SAH additives even at dosages of 50 to 140 kg ha-1 provide a productivity in sandy soils at the level obtainable by treatment with 20% (of the order of hundreds of tons per 1 ha) alluvial deposits. There seems to exist a mechanism allowing the plants to efficiently utilize small water reserves contained in the SAH particles. 

V-Surficial, weakly coherent, alluvial deposits readily eroded by water. (Vj-<3 percent slope V2-<12 percent slope). I-Incompetent, or weakly coherent, bedrock such as shales and tuffs readily eroded by water and (or) prone to mass movement on steep slopes (li-<12 percent slope l2->12 percent slope). C-Competent, or strongly coherent, bedrock such as layered lava flow rocks and igneous intrusives not readily eroded by water, nor generally prone to mass movement except for rockslides and rockfalls from very steep slopes and cliffs (Ci-<12 percent slope). 

Richards, K. (1982) "Rivers Form and Process in Alluvial Channels," Methuen Co., London. 

Meyer, G. A., Wells, S. G., and Jull, A. J. T. (1995). Fire and alluvial chronology in Yellowstone National Park Climatic and intrinsic controls on Holocene geomorphic processes. Geol. Soc. Am. Bull. 107, 1211-1230. 

Brahmaprakash GP, Panda S, Sethunathan N. 1987. Relative persistence of hexachlorocyclohexane, methyl parathion and carbofuran in an alluvial soil under flooded and non-flooded conditions. Agric Ecos Environ 19 29-39. 

The extraction method for prohexadione-calcium in soil was developed using alluvial soil and volcanic ash soil. Extraction by shaking the soil with a mixture of 1N sulfuric acid-acetonitrile (1 3, v/v) and/or of 1N sulfuric acid-acetone (1 3, v/v) showed an acceptable extraction recovery efficiency. 

The method was developed/validated using two typical rice field soils (alluvial soil and volcanic ash soil). In the extraction efficiency study, a soil sample that had been incubated for about 8 months under flooded conditions after addition of... 

In alluvial soil, there was no great difference in the extraction efficiencies among the various solvent combinations tested, with acetone, acidic acetone or alkaline acetone, for reflux extraction. 

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