Permian—triassic boundary in New Zealand

Abstract

Proposed changes to the international Permian-Triassic boundary are reviewed. Evidence suggests that at least the Gangetian interval, or basal Griesbachian “Stage”, should be placed within the Permian Period. The overlying Ellesmerian Substage is more difficult to assess. Although the supposedly Triassic ammonoid Ophiceras may typify the Ellesmerian Substage, it is closely allied to Durvilleoceras woodmani Waterhouse from the Baisalian Substage in New Zealand, of the late Middle Permian Period. Assessment of its benthos is required before the Ellesmerian Substage can be assigned to the Permian or Triassic Period. In this regard the Makarewan fauna of the Takitimu foothills of New Zealand may be of high interest, but the age of the fauna cannot be precisely ascertained until overseas faunas of late Permian or early Triassic age are described in comparable detail. If the Permian—Triassic boundary is elevated to incorporate all or part of the Griesbachian, the lower part of the Snowdon Formation and Wairuna Peak beds, and North Range Group of the Southland Synclinorium may be late Permian, but age control is very poor for these beds. If the Triassic Period were regarded as starting at the incoming of the Smithian (Jakutian) faunas it would be relatively easy to map the Permian—Triassic boundary in New Zealand.