Rock deformation Folds Folds A plunging fold can create A fold consist of two limbs which are divided by an maginary surface called axial plane. The line formed by the intersection of the axial plane and the surface of a rock laver is the fold axis Anticline is a fold with the convex side (therefore oldest layers in the Anticline Syncline is a fold with the concave side m (th Usually anticlines and synclines alternate in the field -Can be"symmetrical"or Folds Anticline, syncline and the "parts of folds Syncline .Beds are bowed downward -Can be"symmetrical"or symmetrical Rock deformation Common fold types Fg.118 Fold Tvpes Fold Types Fold Axis Axial I Limbs dip in ymmetrical F. horizontal vertical opposite directi Asymmetrical F. horizontal inclined opposite directior different angles recumbent over turned Overturned Fold horizontal inclined same direction unbent Fold horizontal horizontal same direction urging Folds inclined2 Rock Deformation Folds A fold consist of two limbs which are divided by an imaginary surface called axial plane. The line formed by the intersection of the axial plane and the surface of a rock layer is the fold axis. Anticline is a fold with the convex side upward (therefore oldest layers in the middle) Syncline is a fold with the concave side upward (therefore youngest layers in the middle) Usually anticlines and synclines alternate in the field. Folds Anticline ïBeds are bowed upward ïOlder beds in core of fold ïCan be ìsymmetricalî or ìasymmetricalî A plunging fold can create ìinterestingî map patterns Folds Syncline ïBeds are bowed downward ïYounger beds in core of fold ïCan be ìsymmetricalî or ìasymmetricalî Fig. 11.7 Anticline, syncline and the ìpartsî of folds Rock Deformation Fold Types Symmetrical F. horizontal vertical opposite direction equal angles Asymmetrical F. horizontal inclined opposite direction different angles OverturnedFold horizontal inclined same direction Recumbent Fold horizontal horizontal same direction Plunging Folds inclined Fold Types Fold Axis Axial Limbs dip in Planes Common fold types Fig. 11.8 symmetrical over turned asymmetrical recumbent