Tertiary strata strike north-west, and in several places the evidence suggests that such a strike follows that of an older pre-Tertiary fold pattern. The great faults formed by the late Tertiary movements have throws often exceeding 3,000 feet, and remarkably straight traces, appearing to be mostly vertical or high-angle reverse faults: there is no evidence suggesting great recumbent folding or nappe-formation in the Tertiary orogenic sequence, although minor overthrusts are known. The Triassic and Jurassic strata are strongly folded and broken by faults formed in pre-Senonian time. The formation of these has been ascribed to the post-Hokonui Orogeny to which is generally ascribed a late Jurassic or early Cretaceous age. Since more recently an Aptian age has been ascribed to beds which are hardly less deformed than the Jurassic strata, it seems possible that this post-Hokonui Orogeny may be in part immediately post-Aptian in age. In many places the strata deformed by these Mesozoic movements show a north-west strike which may be cut across by later Tertiary north-east striking folds and faults. But this north-west strike is not shown everywhere by the Triassic and Jurassic strata. As yet it has been impossible to advance any adequate synthesis of the Mesozoic fold pattern and information on earlier orogenies is even more obscure. It seems likely that there was a great late Devonian or immediately post-Devonian orogeny imparting a generally meridional strike to the lower Palaeozoic strata, but the latter are so much cut by Tertiary faults that the suggestion can only be very tentatively advanced. A general tendency for folds of one age to show a common trend is accepted, although there are many local exceptions. Attention is focused on certain regions where the evidence suggests a considerable change in the trend of folds and faults formed even within a comparatively short space of time, because the time factor in tectonics combined with the idea of posthumous folding appears to shed light on these more abrupt swings in trend ascribed to “syntaxes” and to “arcuate structure”. In the north-east of the North Island, folding of thick Cretaceous and early Tertiary beds along an approximately north-west trend was followed by emergence, planation, subsidence, and sedimentation, and then, after an interval of approximately four Tertiary stages, by folding along a north-east trend, but it is likely that during this interval minor folding along both trends occurred locally. Nevertheless, the dominant trend of the late Tertiary folds in this part of the North Island is north-east and is consistent with the old idea of Marshall and Suess that an anticlinal ridge is likely to continue towards the Kermadec and Tonga Islands. There is no clear evidence of an arcuate swing in the north-east part of the country, because the major fold pattern is only broken by great cross-faults, striking west-north-west. The north-east strike formed by late Tertiary folding is dominant throughout the whole length of the eastern side of the North Island, formerly the site of a geosyncline. An axial chain of Mesozoic greywacke and the great Tertiary and Recent volcanic centre of Rotorua separate the eastern belt from the western Tertiary geosyncline of Macpherson. This axial chain was partly emergent during long periods of Tertiary sedimentation in the western and eastern geosynclines. In the western belt a true arcuate