Fold (geology) - Fold Types

Fold Types

• Anticline: linear, strata normally dip away from axial center, oldest strata in center.
• Syncline: linear, strata normally dip toward axial center, youngest strata in center.
• Antiform: linear, strata dip away from axial center, age unknown, or inverted.
• Synform: linear, strata dip toward axial centre, age unknown, or inverted.
• Dome: nonlinear, strata dip away from center in all directions, oldest strata in center.
• Basin: nonlinear, strata dip toward center in all directions, youngest strata in center.
• Monocline: linear, strata dip in one direction between horizontal layers on each side.
• Chevron: angular fold with straight limbs and small hinges
• Recumbent: linear, fold axial plane oriented at low angle resulting in overturned strata in one limb of the fold.
• Slump: typically monoclinal, result of differential compaction or dissolution during sedimentation and lithification.
• Ptygmatic: Folds are chaotic, random and disconnected. Typical of sedimentary slump folding, migmatites and decollement detachment zones.
• Parasitic: short wavelength folds formed within a larger wavelength fold structure - normally associated with differences in bed thickness
• Disharmonic: Folds in adjacent layers with different wavelengths and shapes

(A homocline involves strata dipping in the same direction, though not necessarily any folding.)