Clastic Soils

The alluvial greatly-clastic soils (layer 15) and eluvial loamy and greatly-clastic deposits with clay filler (layers 16, 17) are developed under deposits of the sandy horizon. It is products of destruction of basement rock. Their development has sporadic character in the profile. 

Various forms of macro- and microelements differ in their ability to migrate and redistribute among the soil profile. The elements contained in clastic minerals are practically immobile. The elements, bound to finely dispersed clay minerals, are either co-transported with clay particles, or are involved in sorption-desorption processes. Part of the elements are found in concretions and also in very thin coating films of hydrated iron oxides some elements make a part of specially edaphic organic compounds. 

Figure 6 shows XRD patterns of the <2 pm fraction (oriented and glycol-solvated) of samples of soils found in the recharge zone. The 17 A, 8.4 A and 5.64 A peaks in the pattern of Edwards soil A show that smectite, not BS I/S, is present in that sample. Furthermore, Edwards soil A does not contain illite, which is present in the Barton Springs suspended sediment. Therefore, Edwards soil A is not the source of the clastic material discharged from Barton Springs. Neither is Edwards soil B, which is also found... 

Furthermore, the existence of carbonates of different origins may complicate the data. Soils derived from matured source rocks, particularly carbonates, always contain very high concentrations of hydrocarbons with compositions of matured oily sources. If the parent rock of the soil was transported by a surface agency such as water, wind or ice, gas anomalies reflect the source area of the sediments rather than the oil or gas potential of the underlying strata. The western part of the Bayinhaote Basin of west China is characterised by Archaean metamorphic rocks covered by thousands of metres of Cenozoic red clastic sediments with no oil or gas potential. Acid treatment of soils revealed very high C1-C5 concentrations (up to 600 pl/kg of C and 70 pl/kg C2). However, it was found that the anomalous soils were derived from carbonate fragments... 

Curtis, C.D. (1990) Aspects of climatic influence on the clay mineralogy and geochemistry of soils, lateosols and clastic sedimentary rocks. J. Geol. Soc., London, 147, 351-357. 

Chelate A dissolved species, typically organic, with two or more funcHonal groups that are capable of sharing pairs of electrons with a metal caHon Clastic Material composed of pieces of pre-exisHng rocks Clay Rock or mineral with a grain size less than 4 fim (for geologists 2 /am for soil scientists), often consisHng of hydrous aluminum silicates... 

This methodology can also be used to classify a soil comprised of mixed sediments, non-clastic sediments, environment-dominated sediments (Figure 7.12), or other sediment types, provided they possess a common parameter that can be expressed quantitatively (e.g., percentage). Four-component sediment systems can be plotted in three dimensions within the faces of a tetrahedron. 

Silts are clastic sediments derived from pre-existing rocks, chiefly by mechanical breakdown processes. They are composed mainly of fine quartz material. Silts may occur in residual soils, but they are not important in such instances. However, silts are commonly found in alluvial, lacustrine, fluvio-glacial and marine deposits. These silts tend to interdigitate with deposits of sand and clay. Silts are also present with sands and clays in estuarine and deltaic sediments. Lacustrine silts are often banded. Marine silts may also be banded. Wind-blown silts are generally uniformly sorted. 

Silts and clays liquid limit greater than 50 Slight to medium Slow to none Slight to medium MH Inorganic silts micaceous or diatomaceous fine sandy or silty soils, clastic silts ... 

A large part of the uranium in igneous rocks is contained in heavy chemically resistant minerals the weathering of which is mainly mechanical. Thus, uranium in such form is transported by rivers and streams as clastic particles that are ultimately found in residual soils, in stream sediments and in common sedimentary rocks, either continental or marine. From the viewpoint of ore deposits the previously mentioned particles may accumulate in placer deposits. 

---