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a layer of straw, peat, sawdust, and other materials used to make a soft, dry, clean and comfortable bed for agricultural animals. Bedding should be hygroscopic and gas absorbent; it should have low heat conduction but great heat capacity. Bactericidal properties are desirable. It is also essential that bedding slow the decomposition of manure, thereby ensuring the manure’s maximal use as a fertilizer. The bedding protects the animals from bedsores, bruises and other injuries, infectious diseases, and colds.
The various materials used for bedding—besides straw, peat, and sawdust—include wood chips, cane, sedge, rush, marsh hay, branches and leaves from trees, coniferous needles, and sand. The best bedding for all animal species consists of peat and straw from winter grasses.
Bedding may be changed daily or periodically. Some types of deep bedding are replaced once or twice a year (as many as three times a year in a poultry house). These require less maintenance but require more bedding material. The frequency at which bedding is changed is determined by the type and quality of the bedding, the animal species, and the system of maintenance.
M. S. NAIDENSKII
a rock structure composed of layers, each of which is distinguished by, among other things, mineralogical composition, color, and characteristics of rock particles. Bedding is typical of sedimentary rocks, constituting one of the most important features. The layers are usually separated from each other by more or less distinct bedding planes. The two types of bedding are the stratification of sedimentary layers and the lamination within a particular layer of rock.
The stratification of sedimentary layers is formed chiefly by strata or beds of rocks differing in various aspects, for example, composition or texture, including the internal lamination. The stratification is classified according to the thickness of the beds as fine, small, large, or very large. Depending on the relative thicknesses of the separate layers, a distinction is made between uniform and nonuniform stratification. The original deposition of strata and beds is usually horizontal, although in some cases it is inclined. Inclined strata result from changes in the material forming the sediment (in the form of a suspension of particles of different sizes or in solution) and from changes in conditions within the region of sedimentation (hydrodynamics, chemical composition of the water, life processes of organisms). These changes are related to seasonal and climatic fluctuations, migration of facies, tectonic movements, volcanic activity, and other factors.
The bedding within a rock layer, known as lamination, appears as a buildup of, in most cases, thin laminae (from a fraction of mm to 1–2 cm), which can differ in the structure of the rock constituents, in mineralogical composition, and in the types of admixtures. The laminae group together to form series separated by more or less distinct boundaries (Figure 1). Depending on the factor responsible for the sediment (chiefly, the dynamic conditions of the deposition environment), the lamination may, depending on the shape and arrangement of the laminae, be horizontal, inclined, or wavy, with intermediate types, such as inclined-wavy and gently sloping wavy also occurring. Horizontal lamination, which ocurs in calm water, is frequently linked with seasonal climatic fluctuations. Inclined lamination derives from different currents, and wavy lamination, from wave movements.
Horizontal bedding is used to determine the position of rocks—that is, the dip and strike. The relative or absolute rate of sedimentation can be ascertained from certain types of horizontal lamination (varved lamination). Inclined bedding is used to determine the direction of sediment movement and sometimes the location of the region that provided the sediment.
Differences in the conditions of formation give rise to several types of bedding. Examples include the cross bedding of windblown material, intermittent-stream bedding, current bedding, bedding caused by wave action in still oceanic waters, and bedding formed by sedimentation in streams, lakes, and deltas.
Depending on its prominence, bedding can be sharply expressed, distinct (with a gradual transition from one layer of lamina to another), or poorly developed (intergrading). With poorly developed bedding, the individual layers (or laminae) cannot be seen, but the direction of bedding can be detected by such features as the arrangement of the inclusions and the orientation of the rock constituents. Bedding is called rhythmic when the elements recur regularly and disturbed when various types of dislocations are present.
Subsequent processes that occur in the sediment during the conversion to rock or after the rock has been formed either emphasize the bedding or, more often, dislocate or alter the original arrangement. Sometimes the change involves the destruction of the bedding, as a result of, among other causes, the activity of benthic organisms, physicochemical processes, metamorphism.
The study of bedding is of great practical and theoretical importance. It figures, for example, in the analysis of facies, in paleogeographic reconstructions, in stratigraphic calculations and the correlation of sedimentary strata, and in prospecting for sedimentary deposits of minerals.
REFERENCESBotvinkina, L. N. Sloistost’ osadochnykh porod. Moscow, 1962 (Tr. Geologicheskogo in-ta A N SSSR, fasc. 59.)
Vassoevich, N. B. “Sloistost’v svete ucheniia ob osadochnoi differentsiatsii.” Isv. AN SSSR: Seriiageologicheskaia, 1950, no. 5.
L. N. BOTVINKINA