Stratigraphic and structural relations of strata enclosing the Dun Mountain Ophiolite Belt in the Arthurton—Clinton region, Southland, New Zealand

Abstract

Abstract Strata lying between the Caples Group and the Murihiku Supergroup in the region between Arthurton and Clinton, Southland, and previously assigned to the Waipahi and Arthurton Groups, consist largely of Maitai Group rock units. Associated igneous rocks belong to the Dun Mountain Ophiolite Belt. Rock units south of the ophiolite belt consist, from south to north, of the Waiua Formation, Greville Formation, and undifferentiated lower Maitai Group. The last unit is restricted to a series offault blocks adjacent to the ophiolite belt and probably includes parts of both the Tramway and Little Ben Formations. The Livingstone-Macpherson Fault System separates the ophiolite belt and Maitai Group from the Caples Group and is up to 3 km wide in this region. It contains faultbounded blocks of volcanogenic sandstone inferred to belong to the Little Ben Formation and red and green sandstone and siltstone, here termed the Watties Sandstone. The latter shows a mixed silicic volcanic and low-grade metamorphic provenance similar to the Caples Group. Sandstones from the Waiua, Greville, and Little Ben Formations were derived from a little dissected magmatic arc of largely intermediate composition. Tramway Formation sandstones show a mixed silicic volcanic and low-grade metamorphic provenance. Boundaries between rock units are faulted. Strata south of the ophiolite belt young essentially to the south except for some fault-bounded blocks of north-younging strata in the Greville Formation.