Of the three main fans of the Waimakariri sector of the Canterbury Plain, underlain respectively by the Burnham Formation, the Springston Formation, and young Postglacial gravel, only the oldest (Burnham) is now thought to be of glacial origin. The Springston Formation, previously thought to be glacial, is interpreted as an aggradation deposit consequent upon rising Postglacial sea level. The young Postglacial fan of the Waimakariri River is the result of subsequent progradation of the coast north of Banks Peninsula.