The folds at Castle Hill (Canterbury) and their bearing on Kaikouran deformation style in the Canterbury Basin

Abstract

The Castle Hill outlier is a structural depression between uplifted ranges of Mesozoic basement. Within the basin the Cretaceous-Tertiary cover is complexly folded into non-cylindrical structures of highly variable profile, plunge and trend. The folds are related to strong but local stresses in the cover induced by faulting of a rigid basement.

Folds of comparable type are widely developed in the northern part of the South Island, and care is needed in their mapping and particularly in their extrapolation beneath cover of gravel or sea. Prediction of concealed folds is further complicated by the intricate pattern of basement faulting partly on trends inherited from the Rangitata Orogeny. It is suggesed that fold patterns and stratigraphic relationships in the regressive late Cenozoic rocks beneath the Canterbury Plains and offshore are likely to be complex.