Field relations of the Constant Gneiss and Greenland Group in the Central Paparoa Range, West Coast, South Island

Abstract

One of the major problems in West Coast stratigraphy has been that of the relation of the Constant Gneiss to the greywacke and argillite of the Greenland Group. Although no contact between the two rock types has previously been recorded, the gneiss has generally been thought to be older than the greywacke, which was considered to overlie it unconformably. In the central Paparoa Range foliation of the gneiss and bedding of the greywacke are parallel and synclinally folded, the gneiss below the greywacke, and each lithology appears to grade into the other. Exposed contacts and the regional field evidence support the probability of the relationship being metamorphic, the Constant Gneiss representing altered Greenland Group. The metamorphism is thought to be associated with the emplacement of the Paparoa Granite.