The two main structures are the Brighstone and Sandown Anticlines, which relate to reactivation of the Needles and Sandown Faults respectively. These anticlines have steep, locally vertical northern limbs, forming the monoclinal structures seen at The Needles, Alum Bay and Whitecliff Bay. In the centre of the island the shortening is transferred between the fault zones, forming the zone of lower dips and north-south strike between Calbourne and Garston's Down. To the north of the monoclines the Paleogene sequence is deformed into a gentle syncline, the Bouldnor Syncline.