Fault Breccias are crumbled up rocks consisting of angular fragments that were formed as a result of grinding and crushing movement along a fault. When rocks deform in a ductile manner, instead of fracturing to form faults, they may bend or fold, and the resulting structures are called folds . Folds result from compressional stresses acting over considerable time. Because the strain rate is low, rocks that we normally consider brittle can behave in a ductile manner resulting in such folds. We recognize several different kinds of folds.
Monoclines are the simplest types of folds.
Monoclines occur when horizontal strata are bent upward so that the two limbs of the fold are still horizontal. . Anticlines are folds where the originally horizontal strata has been folded upward, and the two limbs of the fold dip away from the hinge of the fold. Synclines are folds where the originally horizontal strata have been folded downward, and the two limbs of the fold dip inward toward the hinge of the fold. Synclines and anticlines usually occur together such that the limb of a syncline is also the limb of an anticline. Geometry of Folds - Folds are described by their form and orientation.