FLATTENED PARALLEL FOLDS
1B folds are superimposed by further strain (homo or heterogeneous) to give rise to !C or flattened parallel folds. The amount of strain superimposed can be calculated using the equations given in terms of t', T' and F.
FLATTENING STRAIN RATIO, PHI
Hudleston showed that the values of t' for higher values of limb dip tend to increase in case of folds that are flattened were initially cuspate.