CLEAVAGE

 CRENULATION CLEAVAGE

 LINEATION

REVIEW

FOLIATION

Foliation
 
 

DEFINITIONS
 
 

CLEAVAGE closely spaced discontinuities seen in rocks. Cleavage cuts across beds. One of the causes for cleavage is axial surface foliation

 Crenulation Cleavage: is a cleavage formed as the result of shortening of a pre-existing cleavage.

Lineation: is a parallel alignment of elongate, linear elements in a rock.
 
 

READINGS

 Ch. 12 Read sections pertinent to this lecture

LECTURE : SLIDES OF THE FOLLOWING FEATURES

 (1) The dominant forms of lineation result from the creation of geometric lines at the intersection of bedding surfaces and a foliation.

 (2) Another type of lineation is formed from the intersection of tiny fold hinges of crenulated cleavage and the cleavage surfaces: They correspond to the hinge lines of crenulation folds.

 (3) a third type of lineation results from stretched pebbles. A stretched pebble conglomerate is formed of closely packed elongate clasts

 (4) A fourth type of lineation is formed on the flanks of folds due to layer parallel extension or layer-normal flattening. When the ductility contrast between beds is high and the more ductile beds can flow into the spaces left by the separating and detached coherent blocks in the more competent layers. These structural elements are known as boudins.