New radiolarian age information for the Chrystalls Beach Complex, southwest of Dunedin, New Zealand

Abstract

On the basis of lithology, structural style, and fossil evidence, northern and southern units are recognised within the Chrystalls Beach Complex exposed on the coast south of Akatore Creek, southwest of Dunedin, South Island, New Zealand. Radiolarians including Spongopallium sp. cf. S. contortum Dumitrica, Kozur & Mostler, Eptingium(?) sp., Norispongus(?) sp., and Pseudostylosphaera(?) sp. have been discovered in phosphatic nodules in metamorphosed argillite of the northern unit of the complex. They are regarded as characteristic species of the Middle Triassic (Anisian‐Ladinian). It has previously been known that the more weakly metamorphosed southern unit of the Chrystalls Beach Complex contains moderately well preserved Middle Triassic (Early Ladinian) radiolarian faunas. Together with forms of Tethyan affinity, the faunas in the southern unit contain non‐Tethyan forms including Glomeropyle spp. Aita & Bragin, possibly of Southern Hemisphere high‐latitude origin. These non‐Tethyan forms are also known from the Mahinepua section of the Waipapa Terrane in Northland. Distinctive non‐Tethyan forms such as Glomeropyle Aita & Bragin have not yet been found in the northern unit, the fauna of which includes species that are known from the European Tethys area and which also occur in the southern unit.

Keywords:

• Chrystalls Beach Complex
• Middle Triassic
• radiolarians
• Akatore Creek
• Waipapa Terrane
• Caples Terrane
• Torlesse Terrane