Rd., Mt. Linear fabric; fabric defined by elements that are parallel to a line in space. In areas with multiple generations of fabrics and folds, lineations are typically numbered L1, L2 etc., to correspond with fold and foliation generations. Sometimes the numbering scheme is even extended to bedding, which is labelled S0. It’s almost always a second or later generation of fabric: an initial deformation produces a foliation and later deformation folds that foliation to produce a crenulation lineation. L tectonite in Marblemount quartz diorite, with two generations TYPE OF FEATURE ABBREVIATION FOLLOWED BY STRUCTURAL READING B 123/45 S J 090/23 N SP 123/66 N SL 66/033 FA 13/002 J 040/88 N Planes: B -bedding, J -joint, SP –shear plane Lineation: SL -slip lineation, FA –fold axis 4 planes and 2 lineation are … 87_053. Harrison Lake, BC. L tectonite in Marblemount quartz diorite. 88_098. Linear fabric elements that are elongated, continuous domains. Fabric planes and fold axial surfaces are perpendicular to the shortening direction, the short axis of the strain ellipsoid (Z). A fabric that originated as the rock is formed. [-32.058602,140.034027], 64_238. Schistosity is a coarser grained version of slaty cleavage, and is the term used for a more or less penetrative foliation defined by mineral grains coarser than about 1 mm. Linear fabric defined by parallel alignment of acicular mineral grains; linear equivalent of slaty cleavage and schistosity. A strong secondary planar fabric or foliation. Crenulation lineation is almost always visible when crenulation cleavage is present. This relationship is common because both structures originate from the same strain. 1, 2) are the things that are aligned to give a rock a fabric. Newhalem, WA. The equivalence classes are called the leaves of the foliation. Planar fabric represented by closely spaced fold axial surfaces. Hornblende lineation in orthogneiss. depending on the type of foliation.). Features within a rock that are aligned to give the rock a fabric. Mylonitic lineation: Extreme ductile shearing in shear zones tends to reduce the grain size of mineral grains, while stretching the original grains out into domains of extreme dimensions, and also producing strong crystallographic preferred orientation. Crenulation lineation - penetrative, small-scale (mm’s) fold hinge lines. Fundamental to the description of fabrics is the concept of a fabric element. (literature) The way in which line breaks are inserted in a poem ¹. Lineation in sand layers in garnet schist-perpendicular to Skagit River, WA. Fold lineations. Lineation Lineation is another characteristic commonly seen in metamorphic rocks. Lake, BC. [48.686671,-121.238265], 87_089. Fine-grained rock formed through ductile shearing and dynamic recrystallisation in a shear zone. 85_286. The first line has five syllables, the … Cleavage is thought to develop by a combination of processes including: Slaty cleavage is the defining characteristic of the rock-type slate. Typically, primary lineations in sedimentary and igneous rocks both reflect flow direction. However, the boundaries between these categories have never been formally defined. Lineated dike in gneiss. Glacier Creek. 88_055. [48.686671,-121.238265], 88_093. Secondary fabrics typically indicate that strain has occurred. [48.710028,-121.092539]. Lineation definition is - the action of marking with lines : delineation. Haiku. Define lineation. Foliation of this type is called axial planar foliation (or axial planar cleavage, etc. Group. Strain studies have shown that slaty cleavage typically forms perpendicular to the direction of maximum shortening, the Z axis of the strain ellipsoid. flow lineation), but most are structural. When a foliation is defined by domains that represent identifiable deformed objects in a rock, such as flattened pebbles in a deformed conglomerate, the fabric can be called a flattening fabric. Measuring the intersection lineation is therefore a valuable way of finding fold axis orientations in areas where fold hinges are not well exposed. mica) that are often aligned to produce a fabric. If the folds are reasonably cylindrical, this intersection lineation is parallel to the fold axis. A fold having a strongly curved hinge, so that the geometry resembles a finger of a glove. There are three common types of foliated metamorphic rock: slate, schist, and gneiss. Stretched xenoliths in Breakenridge Orthogneiss. N. Cascade Highway, WA. This lineation takes the form of faint streaks on the cleavage surfaces at a high angle to the fold hinges. In detail, axial planar foliations often depart from exact parallelism with the axial surface of a fold, because of local strain variation. Intersection lineations are formed by the intersection of two planar fabrics. Pressure shadows. The fabric planes or lines can be counted. Definition of Lineation. Common types of lineation, and their origins Primary lineations: Primary lineations are less common … Stretching lineation. It is common to find a lineation that lies parallel to (or in the plane of) a planar fabric. 1. n. Delineation; a line or lines. is pervasive, parallel to the edge of the book, but not visible in the It’s almost always a second or later generation of fabric: an initial deformation produces a foliation and later deformation folds that foliation to produce a crenulation cleavage. Harrison [n -S] Lexicographical Neighbors of Lineation Like most structures, fabrics can be primary or secondary. Needle-shaped, or acicular, mineral grains like amphibole and sillimanite are often aligned to produce a lineation. [49.644646,-121.686745], 89_006. 85_285. area, WA. Long axes of pebbles are plunging to the right. Like their planar counterparts. [48.710028,-121.092539]. A change in the orientation of cleavage caused by differences in the mechanical properties of layers. [49.644646,-121.686745]. Lineated dike in gneiss. Skagit River, WA. Fabric elements (Fig. Big Silver Creek., Slickenside lineation on a bedding plane. In the field, although it’s possible to calculate the intersection lineation from strike-and-dip measurements of the two foliations, it’s usually much more accurate to measure the lineation directly. Big Silver The property of splitting easily parallel to a plane, usually the result of sedimentary compaction. The act of marking or outlining with lines. Lineated dike in gneiss. The axial planar relationship is very useful when disentangling superimposed folds. 2. This is formed by the intersection of any two foliations, such as bedding and cleavage or cleavage to a second cleavage. 88_024. Folds can also be fabric elements, if there are enough of them. The an arrangement or group of lines. Stretching lineation: When a lineation is defined by domains that represent identifiable deformed objects in a rock, such as stretched pebbles in a deformed conglomerate, the fabric can be called a stretching lineations. It’s sometimes called a down-dip lineation from its orientation in areas of gently plunging folds. It is not possible to count the number of fabric planes or lines; It is not possible to see spaces between the fabric planes or lines. This structure is identical to those shown in the Cascades. The front surface is nearly perpendicular to the top surface of L/S-tectonite - a strong foliation and a strong lineation. 58.390816, -5.141011]. 2. 87_147. Sometimes deformed rocks contain domains or layers of different composition that can be shown to have originated as a result of solution of particular minerals. Extreme ductile shearing in shear zones tends to reduce the grain size of mineral grains, while stretching the original grains out into domains of extreme dimensions, and also producing strong crystallographic preferred orientation. 58.548691, -4.453772]. 67_104. Planar fabrics are also called foliations. Lewisian gneiss with lineation and folds. A foliation is any sort of fabric-forming planar or curved planar geologic structure in a metamorphic rock, but could additionally include sedimentary bedding or magmatic layering (Wilkerson, 2019). Working with Stereographic Projections. Vertical lineation in chert, left, and quartz diorite (in columns bordering church windows. Whenever two intersecting foliations are present, there is always an intersection lineation defined by their intersection. Hallett Cove, South Australia. 88_081. Individual fabric planes or lines can be counted and the spaces between them can be discerned. Originally Published: September 8th, 2014 Rebecca Hazelton is the author of Fair Copy (2012), winner of the Ohio State University Press/ The Journal Award in Poetry, and Vow (2013), from Cleveland State University Poetry Center. River, WA. Examples of primary fabric are bedding in sedimentary rocks and flow banding in igneous rocks. If the manifold and/or the submanifolds are required to have a piecewise-linear, differentiable (of class Cr), or analytic structure then one defines piecewise-linear, differentiable, or analytic foliations, respectively. Definition of Lineation. Noun. Skagit River, WA. Lineation, parallel to hammer, and conjugate joints in Moine [48.719089,-121.071253], 88_103. Pencil slates result from almost equal spacing of bedding and cleavage a division into lines. Geological Structures: A Practical Introduction, • Lab 2. For example, some slates can be split almost anywhere: there’s effectively an infinite number of cleavage planes. Numerous closely spaced fold hinges may produce a lineation in highly deformed rocks. Any penetrative structure that gives a rock different properties in one direction relative to another. 88_102. Ketchum Creek., Newhalem, WA. A lineation may be a primary igneous or sedimentary fabric element, such as an array of elongate K-feldspar porphyroblasts, inclusions or pebbles oriented with their long dimensions mutually parallel, or flute casts. ¹ Source: wiktionary.com. This leads to a second important concept: the idea of a penetrative fabric. 5. A fabric that is not present everywhere in the rock, when observed at a given scale. fractures. [49.644646,-121.686745]. surface that slopes to the right. Physical rotation (transposition) of mineral grains as a rock is deformed; Solution of grains subjected to high stress (pressure solution); Growth of new mineral grains during deformation. Some slaty cleavages are penetrative down to the scale of individual mineral grains; others show domains under the microscope. Cleavage typically bends so that it is more perpendicular to competent layers, and more parallel to incompetent layers. 64_241. Fabrics may be planar or linear. Lineation Return to [] Linear structures can be sedimentary (e.g. Generally, a lineation is a term used to describe linear elements in a rock, this can occur in deformed or undeformed rocks (Fossen 2016). In the Cascades, the main deformation is about 90 Ma; the youngest Individual fabric planes or lines cannot be counted. Change in size and shape (dilation and distortion). Platy or flake-shaped mineral grains (e.g. A lineation defined by the intersection of two differently-oriented foliations. Closely spaced fractures can produce a type of cleavage called fracture cleavage. Boudinage. An outline. [NC573649. Intersection lineation: Whenever two intersecting foliations are present, there is always an intersection lineation defined by their intersection. Foliation, planar arrangement of structural or textural features in any rock type but particularly that resulting from the alignment of constituent mineral grains of a metamorphic rock of the regional variety along straight or wavy planes. Lineations are geometrical arrangement of component features in the rock (fabric element) in which one dimension is considerably longer than the other two dimensions, as seen in the diagram below (Fossen 2016). Foliations are often developed parallel, or roughly parallel, to the axial surfaces of folds (Fig. These will be considered in more detail when we deal with mylonites later in the course. These relationships show the deformation was after the dike intrusion. (geology) A linear feature in rock, often structural ¹. Linear fabric defined by elongated domains, produced by extension. [-45.881214,170.468445], 88_022. Platy or flake-shaped mineral grains like mica are often aligned to produce a foliation. Rocks with a strong tectonic lineation that lies in the plane of a tectonic foliation are sometimes called LS-tectonites. the photo on the left. Stretched clasts in a sedimentary rock can produce a lineation if they are all aligned parallel to a line. There is no universal agreement on the definition, but typically defined by mineral grains between 0.1 and 1 mm diameter.

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