Abstract

An analysis of faulting in the late Miocene volcanic rocks of Banks Peninsula, South Island, New Zealand, shows that the formation of the volcanic edifice was largely controlled by NE–SW-striking dextral-oblique strike-slip faults. The data show a variable component of west–east- or NW–SE-oriented shortening and north–south or NE–SW extension. Synvolcanic faults reactivated Cretaceous normal faults and are interpreted to have formed a local pull-apart basin that controlled volcanism. Further east, the geometry of Akaroa Harbour is controlled by a north–south-striking oblique reverse fault. Limited fault-slip data collected from sub-recent loess deposits are not significantly different from the data collected in the volcanic rocks and appear to show that the kinematic field did not change significantly over the last c. 10 Ma. The overall kinematic field causing the recent series of earthquakes in the greater Christchurch region is also not fundamentally different from the one that controlled the eruption of the volcanic rocks. We conclude that the inherited Cretaceous faults controlled the development of the late Miocene volcanism on Banks Peninsula and largely provided a major anisotropy along which the recent faults ruptured.

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