Linear Structural Elements

Lineation is a general term to describe any repeated, commonly penetrative and parallel alignment of linear elements within a rock (to envision lineation, imagine packages of spaghetti). 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. The primary alignment of markers is correlated with the direction of flow of magma or paleocurrent and form flow lines. Structural geology is particularly concerned with lineations produced by deformation. Lineations due to ductile deformation actually lay on foliation planes and are therefore as penetrative as foliations. A single deformation may produce several sets of lineations with different orientations within a given foliation plane. Lineations are referred to as L-elements of the rock fabric. Where L-lines of different generations are present in the same fabric, they are given numerical suffixes according to relative age: 0 L is the