Preliminary report on Lower Jurassic radiolaria of Gondwana origin from the Kawhia coast, New Zealand

Abstract

Abstract Well‐preserved radiolarians from the Newcastle Group in southwest Kawhia, New Zealand, constitute the first record of Lower Jurassic radiolarians from in situ deposits in high latitudes of the Southern Hemisphere on the margin of Gondwana. The radiolarians were extracted from carbonate nodules from five horizons in the Rewarewa Formation and the lower part of the Arawhero Formation, in the Murihiku Terrane. The radiolarian‐bearing sequence, which lies within the upper part of the type section of the local Aratauran Stage, is roughly datable as Hettangian‐Sinemurian from rare ammonite occurrences. The radiolarian assemblages consist, on average, of 80–90% spumellarians and 10–20% nassellarians. Spumellarians include species of the following genera: Archaeotriastrum, Crucella, Emiluvia (?) Homeoparo‐riaella, Orbictilifomaa, Pantanellium, Paronaella (?), Pseudocrucella, PseIIdoheliodiscus, Spon‐gostaurus and Spongotrochus. Nassellarians are composed of species of Ragotum, Bipedis, Droltus, Jams (?) Perispyridium (?) Raoultius, Riedelius, Saitoum and Thetis. From data of Lower Jurassic radiolarian faunas of Europe, North America and Japan, the New Zealand fauna shows stronger affinity with those of the European Tethys such as Turkey (e.g. De Wever 1982) and the Northern Alps (Kozur & Mostler 1990) than with faunas from other areas of the circum‐Pacific. This connection between the European Tethyan and New Zealand faunas is not well explained by presently accepted continental reconstructions (Smith et al. 1994) for the Early Jurassic.