با درود...
نمی دونم چه ربطی به ساینس دایرکت و السیور داره و همچنین اینو نفهمیدم که مهندسی صنایع برای چی با این دو تا افق سر و کار داره
ولی به هرحال منبع خاکشناسان جهان در سیستم رده بندی آمریکایی کلیدهایی هست که هر چد سال یکبار منتشر می شه و براتون میارم....
امیدوارم به کارتون بیاد....
An argillic horizon is normally a subsurface horizon with a
significantly higher percentage of phyllosilicate clay than the
overlying soil material . It shows evidence of clay
illuviation. The argillic horizon forms below the soil surface,
but it may be exposed at the surface later by erosion.
Because there is little or no evidence of illuvial clay
movement in soils on the youngest landscapes, soil scientists
have concluded that the formation of an argillic horizon
requires at least a few thousand years. On some late-
Pleistocene landscapes, argillic horizons are more strongly
expressed in soils under forest vegetation than in soils under
grass. Therefore, the kind of flora and associated fauna is
thought to have an influence on the rate of development or
degree of expression of the argillic horizon. Climate also is a
factor. There are few or no examples of clay films in soils with
perudic soil moisture regimes, such as the soils in parts of
southeastern Alaska, the Olympic Peninsula of Washington,
and the British highlands where water percolates through the
soils during all seasons. Argillic horizons are common on the
adjacent lowlands in Great Britain, under climates where the
soils undergo wetting and drying cycles.
Textural differentiation in soils with argillic horizons results
from one or more processes acting simultaneously or
sequentially, affecting surface horizons, subsurface horizons, or
both. The degree to which a process or several processes
operate varies widely from soil to soil. In some soils clay
illuviation is significant, while in others clay illuviation is
overshadowed by in situ weathering. Not all of the processes
are completely understood. The ones thought to be most
important are summarized in the following paragraphs.
1. Clay eluviation and illuviation.—Some suspended clay
is carried downward in the soil water. The movement of clay
can take place from one horizon to another or within a horizon.
There is a strong mineralogical similarity between the fine clay
in an eluvial horizon and that in a deeper illuvial horizon. This
similarity supports the idea that clay migrates dominantly as
clay rather than as the products of decomposition that were
later synthesized to form clay-sized particles.
Clay mobility is influenced by a number of factors. If clay
platelets are aggregated by sesquioxides or other cementing
agents, the cement must be dissolved prior to clay movement.
Phyllosilicates with thick, diffuse double layers of adsorbed
cations are dispersed more easily than those with thin double
layers. If the ionic strength of the soil solution is high, clays
tend to flocculate. Wetting a dry soil seems to lead to disruption of the fabric and to dispersion of clay unless the ionic
concentration is high. Sodium ions in solution, between critical
limits of activity, increase clay dispersion. Optimal clay
dispersion occurs when the pH at the zero point of net charge
on the clay particle is distinctly different from the pH of the
soil solution. This dispersion commonly occurs between pH
In soils that are periodically dry, the clay suspension moves
downward and stops in the dry subsoil as the soil solution is
absorbed. During absorption of the soil solution, the surface of
the ped acts as a filter and keeps clays from entering the
interior of the ped. The clay platelets then coat the surface of
the ped or void wall and are oriented with their long axes
parallel to the surface on which they were deposited. They are
called clay films. These layers of oriented clay can be
distinguished from the rest of the clay through the use of a
petrographic microscope.
As soil solution enters unsaturated subsoils, water
movement occurs in fine pores. Pore water velocity is reduced
as a function of pore wall friction. Some clay deposition may
occur simply because fluid velocity is too low to keep the clay
Capillarity affects water movement both downward and into
the peds. If a soil horizon is underlain by a horizon of
considerably coarser texture (i.e., larger pores), capillary
continuity is broken and water tends to remain in the fine
capillaries above the zone of contact. When water evaporates or
is withdrawn by roots, suspended and/or dissolved materials,
including clay, are left. This action accentuates the original
difference in pore-size distribution, and clay is deposited
directly above the coarse textured strata or lenses.
Clays that are deposited from suspension in sediments, such
as shale or glacial till, are commonly oriented parallel to the
depositional or stress surface. In contrast, clays formed in place
within the soil generally are oriented according to the crystal
structure of the original mineral grains from which they
formed. Neither the mineral grains nor the planes in the shale
or till are consistently oriented with respect to any pedogenic
features. Consequently, the thin sections of many soils indicate
layers of oriented clays in peds and on the surfaces of pores and
peds.