Stratigraphic, structural, and metamorphic relationships in the Dansey Pass area, Otago, New Zealand
Abstract In the Dansey Pass area, greywacke, semischist, and schist on the north-eastern margin of the Otago schist arc show a progressive increase in metamorphic grade from prehnite-pumpellyite to greenschist facies, or in terms of textural development, from non-foliated greywacke of textural zone 1 to laminated schist of textural zone 3B. Locally a stratigraphic sequence some 15000 m thick can be recognised, in which the metamorphic grade increases towards the top. The rocks have been affected by four periods of folding. The earliest phase, probably initially penecontemporaneous with the later stages of sedimentation, resulted in steeply dipping strata, overturned throughout extensive areas. Phase II folding may have commenced as the early phase progressed, as early Phase II structures show evidence of soft sediment deformation, although other evidence indicates that Phase II continued until well into the metamorphic event. Isograds and isotects are not folded by Phase II structures, however, indicating...