Juxtaposition of Tethyan and non-Tethyan Mesozoic radiolarian faunas in melanges, Waipapa terrane, North Island, New Zealand

Abstract

Red cherts from Kawakawa Bay near Auckland have yielded Late Triassic and Early Jurassic radiolarians. The cherts occur as blocks in melanges that have a green argillite matrix containing Middle and Late Jurassic (Callovian-Oxfordian) radiolarians. The melanges mark fault zones along which the Waipapa terrane has been imbricated. Callovian-Oxfordian green argillites are also found in stratigraphic contact with overlying Kimmeridgian-Tithonian green argillites and gray terrigenous clastics. The Late Triassic and Early Jurassic radiolaria are Tethyan, but the Middle and Late Jurassic faunas are dominantly non-Tethyan because the two sets of faunas are of low-latitude and of high-latitude origin, respectively, or because they originated in areas of differing ocean productivity. Occurrence of both Late Triassic and Early Jurassic radiolarians in one red chert horizon indicates sedimentary reworking.