The well indurated greywacke-argillite rocks of the Porirua district have been subjected to strong folding followed by more than one period of intense faulting and fracturing. The main axis of flexural folding trends NNE-NE and plunges 14° to 17° NE. Numerous small-scale fold; are described. They exhibit a wide range of forms: from open, symmetrical, and faulted fold; to isoclinal folds. A few localized folds, described as incongruous, have axes that cut across the NNE-NE trending regional fold axis.