Cleavage, foliation, lineation
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Rock fabric is defined as the total sum of grain shape, size, and configuration in a rock. Foliation is a planar fabric that can include cleavage, which refers to spaced, aligned planar or curviplanar surfaces associated with folds. Lineation is a linear fabric that represents the subparallel alignment of elongate elements within a rock. Both foliation and lineation can be primary features that formed during the original igneous or sedimentary processes or can be secondary features formed by metamorphism.
Cleavage, foliation, lineation
- 1. Cleavage, Foliation, Lineation • Rock fabric: Total sum of grain shape, grain size, and grain configuration in a rock. • Foliation is a planar fabric – Cleavage is a common kind of foliation • Lineation is a linear fabric – See Chapter 8, D+R
- 2. Cleavage • Rock cleavage: Broadly refers to spaced, aligned, planar to curviplanar surfaces that tend to be associated with folds and oriented parallel to or fan-shaped relative to the axial surfaces. Commonly penetrative and form without apparent loss of cohesion. – See Chapter 8, D+R
- 10. Foliation • “…mesoscopically penetrative parallel alignment of planar fabric elements in a rock, usually in a metamorphic rock” – Can be primary (igneous or sedimentary)
- 11. Primary foliation in a volcanic rock
- 13. Lineation • “…subparallel to parallel alignment of elongate, linear fabric elements in a rock body, commonly penetrative at the outcrop and/or hand sample scales of observation” – Can be primary (igneous or sedimentary) – Includes slickenlines
- 16. Lineation