Silurian rocks and fossils at Hailes Knob, North-West Nelson, New Zealand

Abstract

A small brachiopod fauna, including Conchidium sp., ?Isorthis sp., ?Dalejina sp., ?Amphistrophia from the Hailes Knob Quartzite near Upper Takaka is described and shown to be of Middle or Upper Silurian age (Wenlockian or Ludlovian)—the first New Zealand Silurian fossils. The fauna helps to fill an important gap between Upper Ordovician and Lower Devonian in New Zealand's older Paleozoic faunal sequence. The Hailes Knob Quartzite, 650 ft (200 m) thick, conformably overlies Arthur Marble (formerly Mount Arthur Marble, Upper Ordovician) and is confined to the core of a small north-trending syncline forming the crest of the Pikikiruna Range. Overlying beds are not preserved. The formation is composed of predominantly quartzitic sediments and becomes coarse-grained in its uppermost beds, to which the fossils are confined. The contact with Arthur Marble, and a section through the formation are well exposed and are described in detail. Previous opinions on the age of the Arthur Marble and on strata formerly thought to be Silurian are reviewed.