Lower Paleozoic rocks between Upper Takaka and Riwaka, North-West Nelson

Abstract

Lower Paleozoic rocks in the southern Pikikiruna Range and adjoining area in North-west Nelson are divided into five formations and a group comprising two informal units.The Riwaka Group and the Hailes Knob Quartzite are new units that are formally denned. Fossils are rare and are poorly preserved. Corals from the Mt Arthur Marble and from a marble band on the west side of the Takaka Valley are of Uppermost Ordovician age, and from stratigraphy the full rock sequence, some 17,000 ft thick, is inferred to range from Upper Ordovician through Silurian possibly to Devonian.Metamorphic grade of rocks of the same age increases to the east, and the Riwaka Group (gneiss, diorite, and amphibolite) and the Separation Point Granite are thought to be derived from metamorphosed volcanic and sedimentary formations