ABSTRACT
In the folds studied so far, the axis of the fold has been horizontal. The axis is the intersection of the axial plane with any bedding plane. (Make a synclinal fold by taking a piece of paper and folding it in two to make a simple V-shape. Drop a pencil into this and it will assume the position of the axis of the fold.) Such a fold, with the axis horizontal, is called a ‘non-plunging’ fold. The outcrops of the limbs tend to be parallel (but of course are affected by the configuration of the ground) since the structure contours drawn on one limb are parallel to those drawn on the other limb. (They have, as well, been parallel to the axial plane and, in cases where the axial plane was vertical, parallel to the axial trace (= outcrop of the axial plane).)
