foliation


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foliation

1. Botany
a. the process of producing leaves
b. the state of being in leaf
c. the arrangement of leaves in a leaf bud; vernation
2. Architect
a. ornamentation consisting of foliage
b. ornamentation consisting of cusps and foils
3. any decoration with foliage
4. Geology the arrangement of the constituents of a rock in leaflike layers, as in schists

Foliation

 

the ability of rocks to split relatively easily parallel to a certain plane when struck. This mechanical anisotropy of rocks is caused by dynamic metamorphism in which the platy and rodlike grains of micas, hornblende, chlorites, and other minerals that make up a rock take on an identical orientation as a result of recrystallization or rotation. In irregularly shaped grains of minerals, orientation of the optical axes of the grains and other crystallographic characteristics may be observed. Petrotectonic analysis is used to study the rules of orientation and the rules for decoding the motions that cause the orientation.

Foliation may be regional, manifesting itself over large areas, or local, related to shifts along tectonic displacements. It frequently occurs during rock folding, with the foliation usually subparallel to the axial planes of the folds. Foliation also forms in cleavage: the crystals are flattened in a plane perpendicular to the axis of compression and the rock acquires a plane-parallel oriented internal structure. Some geologists use the term “cleavage” as a synonym for “foliation.”

REFERENCES

Pek, A. V. Treshchinnaia tektonika i strukturnyi analiz. Moscow-Leningrad, 1939.
Fairbairn, H. W. Strukturnaia petrologiia deformirovannykh gornykh porod. Moscow, 1949. (Translated from English.)

A. V. PEK

foliation

[‚fō·lē′ā·shən]
(botany)
The process of developing into a leaf.
The state of being in leaf.
(geology)
A laminated structure formed by segregation of different minerals into layers that are parallel to the schistosity.
(metallurgy)
Beating metal into thin sheets.

foliation

1. The cusps or foils with which the divisions of a Gothic window are ornamented.
2. Leaf-like decoration.
References in periodicals archive ?
The anisotropy of mechanical properties was determined based on the interpretation of uniaxial loading tests on specimens with different dip of foliation. The specimens with oblique foliation had lowest peak strength.
ii + 444 (see further the discussion of the foliation below).
Close to the contact, the fabric in micaceous rocks typically shows the development of a new crenulation cleavage overprinting the generally planar foliation, and more quartz-rich rocks display moderate to strong cataclasis with undulose extinction and bent mica grains (Fig.
Foliation and lineation in garnet amphibolite are parallel to sub-parallel to those found in the mylonitic peridotite.
Layers or Foliation: Rock masses generally contain layers of different rocks with varying strengths and characteristics.
Foliation is erroneous as it starts twice, renumbering folio 3 as 1, and going on thereafter to the end, with the following errors: folio 17 has been numbered twice, a folio has been omitted between folios 127 and 128, and folio 162 has been doubled.
Note that, since [xi] is Killing and [L.sub.[xi]][phi] = 0, the metric g and the tensor field [phi] locally project along the leaves of the 1-dimensional foliation defined by [xi], respectively, onto a Riemannian metric g' and a tensor field J' such that (J', g') is a Kahlerian structure on the space of leaves [M'.sup.2n] = [M.sup.2n+1]/[xi].
It can be easily proved that the collection of half-planes [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] is a foliation of [[DELTA].sup.+], hence for every point of the domain [[DELTA].sup.+] there exists one and only one half-plane [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII], with [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] [member of] [Adm.sub.k], containing the point itself.
Assume that there exists a foliation F of M such that vN = TF [|.sub.N] is a normalization of N.
Interestingly, detailed inspection of the orientation distribution of crystal directions and planes with respect to the tectonite reference system (foliation and lineation) allows us to discuss the activity of different mechanisms during deformation (e.g.
In contrast, prisms in most representative species of the orders Pectinoida and Ostreoida (families Propeamussiidae, Pectinidae, Anomiidae, and Ostreidae) show a clear internal structure consisting of a remarkable foliation (Fig.