Reclined folds and coaxial refolding in the paleozoic rocks of North-West Nelson

Abstract

Abstract Complex folding in Ordovician shales and quartzites adjacent to a large granite intrusion is clearly visible on high dtitude vertical air photographs of the Gouland Downs in North-West Nelson. An almost complete absence of sympathetic mesoscopic folding and the partial obliteration of fabric elements associated with the deformation by post-tectonic contact metamorphism hinders the interpretation of the structure. Most of the folds, however, appear to be isoclinal with axes that plunge steeply to the east or north-east, almost at right angles to the trend of the folds. The emplacement of granite caused further folding in one area, apparently coaxial with the earlier deformation. Almost all the recognisable fold noses close to the south and are synforms, and it appears likely that they are small nappe-type folds separated by thrust planes. The Slate Range Fault, a large late Tertiary feature probably related to the Wakamarama Fault, crosses the area and a sinistral component of 2,800 ft is estimated.