Difference between revisions of "Lithological discontinuity (WRB)"
imported>Thierry Daunois (Created page with ''''Lithological discontinuity''' is one of the diagnostic properties used, in the WRB system, to discriminate some soils from others. ==Description== The term Lithological disco...') |
imported>Jacques Ducloy m (5 revisions imported) |
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==Description== | ==Description== | ||
| − | The term Lithological discontinuity | + | The term "Lithological discontinuity" (from Greek ''lithos'', stone, and Latin ''continuare'', to continue) refers to significant changes in particle-size distribution or mineralogy that represent differences in lithology within a soil. A lithological discontinuity can also denote an age difference. |
==Criteria== | ==Criteria== | ||
| − | + | A lithological discontinuity requires one or more of the following : | |
| + | * an abrupt change in particle-size distribution that is not solely associated with a change in clay content resulting from pedogenesis | ||
| + | or : | ||
| + | * a relative change of 20 percent or more in the ratios between coarse sand, medium sand, and fine sand | ||
| + | or : | ||
| + | * rock fragments that do not have the same lithology as the underlying continuous rock | ||
| + | or : | ||
| + | * a layer containing rock fragments without weathering rinds overlying a layer containing rocks with weathering rinds | ||
| + | or : | ||
| + | * layers with angular rock fragments overlying or underlying layers with rounded rock fragments | ||
| + | or : | ||
| + | * abrupt changes in colour not resulting from pedogenesis | ||
| + | or : | ||
| + | * marked differences in size and shape of resistant minerals between superimposed layers (as shown by micromorphological or mineralogical methods) | ||
| + | |||
| + | '''Additional characteristics''' : in cases, a horizontal line of rock fragments (stone line) overlying and underlying layers with smaller amounts of rock fragments or a decreasing percentage of rock fragments with increasing depth may also be suggestive of a lithological discontinuity, although the sorting action of small fauna such as termites can produce similar effects in what would initially have been lithologically uniform parent material. | ||
==RSG in which lithological discontinuity can be observed== | ==RSG in which lithological discontinuity can be observed== | ||
| Line 17: | Line 32: | ||
* The [http://www.fao.org/ag/agl/agll/wrb/doc/wrb2007_corr.pdf FAO reference text], (2007 version) | * The [http://www.fao.org/ag/agl/agll/wrb/doc/wrb2007_corr.pdf FAO reference text], (2007 version) | ||
| + | |||
| + | [[Category:Diagnostic properties (WRB)]] | ||
Latest revision as of 18:24, 28 June 2017
Lithological discontinuity is one of the diagnostic properties used, in the WRB system, to discriminate some soils from others.
Contents
Description
The term "Lithological discontinuity" (from Greek lithos, stone, and Latin continuare, to continue) refers to significant changes in particle-size distribution or mineralogy that represent differences in lithology within a soil. A lithological discontinuity can also denote an age difference.
Criteria
A lithological discontinuity requires one or more of the following :
- an abrupt change in particle-size distribution that is not solely associated with a change in clay content resulting from pedogenesis
or :
- a relative change of 20 percent or more in the ratios between coarse sand, medium sand, and fine sand
or :
- rock fragments that do not have the same lithology as the underlying continuous rock
or :
- a layer containing rock fragments without weathering rinds overlying a layer containing rocks with weathering rinds
or :
- layers with angular rock fragments overlying or underlying layers with rounded rock fragments
or :
- abrupt changes in colour not resulting from pedogenesis
or :
- marked differences in size and shape of resistant minerals between superimposed layers (as shown by micromorphological or mineralogical methods)
Additional characteristics : in cases, a horizontal line of rock fragments (stone line) overlying and underlying layers with smaller amounts of rock fragments or a decreasing percentage of rock fragments with increasing depth may also be suggestive of a lithological discontinuity, although the sorting action of small fauna such as termites can produce similar effects in what would initially have been lithologically uniform parent material.
RSG in which lithological discontinuity can be observed
See also
- The FAO reference text, (2007 version)
