Paleomagnetic constraints on the tectonic rotation of the southern Hikurangi margin, New Zealand

Abstract

Plate reconstructions of the New Zealand region indicate substantial Cenozoic tectonic rotation of the Hikurangi margin. This study was undertaken to determine the rotational history of the northern Marlborough paleomagnetic domain in the southern part of the Hikurangi margin. Most Cenozoic rocks in the Marlborough region are unstably magnetised, and useful results were obtained only from late Miocene ‐ early Pliocene strata (c. 8–4 Ma). Clockwise rotations, with respect to the Pacific plate, between the Wairau and Kekerengu Faults are consistently about 20° and occurred after c. 4 Ma. No rotation is observed in the interval between 8 and 4 Ma, in contrast with the northern part of the Hikurangi margin where rotation has been continuous since the early Miocene. Differential rotation between northern Marlborough and eastern North Island is likely to have occurred about the northern end of the Wairau Fault in Cook Strait. Rapid rotation throughout the Hikurangi margin since the early Pliocene may be linked to a change in the motion of the Pacific plate relative to the Australian plate.

Key words:

• paleomagnetism
• Marlborough
• tectonics
• rotation
• Hikurangi margin
• Miocene
• Pliocene