New paleomagnetic results from Blind River: Revised magnetostratigraphy and tectonic rotation of the Marlborough region, South Island, New Zealand

Abstract

Part of the Upper Miocene-Lower Pliocene mudstone section at Blind River, northern Marlborough, which was the subject of a paleomagnetic study by Kennett and Watkins in 1974, has been resampled and the data reinterpreted. The new results do not concur entirely with those of Kennett and Watkins. In particular, we do not find the uppermost normal event of their record. This implies a more uniform deposition rate and a later date of 5.6 m.y. for the first occurrence of Globorotalia conomiozea in the section. The new data also show a declination anomaly of 36 ± 4° to the east. This is thought to be due to clockwise rotation within the active tectonic belt of New Zealand, between the Pacific and Australian plates. This declination anomaly is slightly larger than those reported from sites in the northern part of the tectonic belt, suggesting that the deformation is more complex than a simple block rotation.