Folds classification Fold's geometrical classification: a.Symmetrical fold: It is a kind of fold that the axial plane of fold is vertical, and fold has two symmetrical sides.   b.Asymmetrical fold: It is a kind of fold that the axial plane of fold is not vertical, and fold has two asymmetrical sides.   c.Overturned fold: It is a kind of fold that its axial plane is oblique and both sides of fold have a dip in the same direction. The dip of both flanks is different and one of them is overturned.   d.Recumbent fold: When the axial plane is horizontal, the fold is called recumbent.   e.Isoclinal fold: This term is used for folds having dips in the same direction and equal sizes. The flanks of this fault may be horizontal, vertical or oblique.   Recumbent Isoclinal folds in marble. Mosaic Canyon, Death Valley, CA.Note pen for scale. Upright isoclinal anticline in Stanley Shale, Arkansas. Arrows, on the same bed, point stratigraphically upward. f.Chevron fold: If both flanks have an acute angle with each other, then this fold will be called chevron fold.   Chevron folds in ribbon chert. Marin County, CA. g.Fan fold: It is a fold that its two flanks are in an overturned condition. In anticlinal fan fold the dips of both flanks are toward each other, whereas in synclinal fan fold the dip of two flanks are opposite to one another.   h.Double plunge fold: If the fold hinge has dip on both sides is called double plunge fold.   i.Dome: It is an anticline which does not have a clear strike. On the other hand, layers' dip in all parts is toward outside.   j.Basin: It is a syncline does not have clear strike and axis, but layers' dip is toward central part.