This thesis maps and describes the geology of the Upper Cretaceous-Tertiary rocks occurring in the Northern Waiau Basin, lying between the Lottery and Mason Rivers, and occupying approximately 250km₂ of study area.

The basin is composed dominantly of sedimentary and volcanic rocks, unconformably overlying a basement of Torlesse Supergroup characterised by alternating sequences of lithic to quartzo-feldspathic sandstones and mudstones containing conglomerates of volcanic and reworked Torlesse clasts. The Upper Cretaceous-Tertiary sediments display a wide range of lithologies including conglomerates, sulphurous mudstone, calcareous silty sandstone and limestone, reflecting a fluctuating fluviatile-shallow marine depositional environment. The Haumurian part of the sequence is notable for the occurrence of large lenticular bodies of conglomerate (Stanton Conglomerate) which are rare elsewhere in North Canterbury and South Marlborough.

Lower Tertiary basaltic intrusions unconformably penetrate Upper Cretaceous calcareous mudstone and siltstone, in the eastern and western parts of the study area. The lower Tertiary sequence again differs here because of the presence of a very thick sequence of Whaingaroan basaltic tuff, conglomerate and lava flow (Cookson Volcanics Group) succeeded by a thick, but lensoidal shaped body of bryozoan-molluscan-brachiopod biosparite limestone (Isolated Hill Limestone Member) of Duntroonian-Waitalcian age. Deepening of the basin, marked by the fine silts and muds of the Greta Formation completes the Tertiary sequence beneath a regional unconformity.

The major southwest-northeast trending Hope Fault occurs in the northwestern part of study area. This fault zone lies within the axial tectonic belt of Walcott (1978). The oblique convergent vector results in a hybrid strike slip and compressional regime. The strike slip movement along the curved section of the fault has resulted in secondary thrust and strike slip faulting.

A shear couple formed between the Hope Fault and Rahi fault to the south generated the most structurally important feature, the major Wandle En Echelon Fold system, occupying the centre of the basin. Buckling of the folds in Tongaporutuan time preceeded truncation, rotation and overtuning of the syncline limbs against the Hope Fault during the later stages of the Kaikoura Orogeny. Late Pleistocene uplift north of the fault shed fluvio-glacial tills and outwash across the basin as aggradational terraces surfaces cut by recent offsets on the active fault traces.