A Lower Tertiary Décollement on the East Coast, North Island, New Zealand

Abstract

A south-west directed décollement of Lower Tertiary rocks is recognised from a region in which the principal Cretaceous to Recent strike is north-east-south-west, A series of at least 20 thrust slices rests on an almost completely undisturbed autochthon. The stratigraphy and structures within the décollement are described and two distinct phases of movement are recognised. The possible mechanisms by which the décollement could have been produced are discussed and it is concluded that individual slices or groups of slices slid south-west wards under gravity from an elevated region centred some 20 miles to the north-east of the accompanying map area. The lowest five slices differ from the rest in several respects and may have been formed and pushed forwards by the movement of those behind.