Petrology and structure of the south-eastern Marlborough Sounds, New Zealand

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Vitaliano, C. 1968 Petrology and structure of the south-eastern Marlborough Sounds, New Zealand. Wellington: Government Printer. New Zealand Geological Survey bulletin 74 40 p.

Abstract: Geologic mapping in the Marlborough Sounds, near Picton, New Zealand has delineated a series of schists of greenschist facies. The rocks have been classified in subzones Chl. 1 to 4 according to the criteria established for similar rocks in the Otago district. The schists of subzones Chl. 3 and 4 occupy a north-easterly-trending zone, flanked on either side by thick sequences of greywackes belonging essentially to subzones Chl. 1 and Chl. 2. The schists are jointed, folded, and faulted. Jointing is prevalent throughout the region, occurring with equal frequency in all subzones. The fault pattern consists of major faults, restricted mainly to areas covered by large bodies of water, and numerous minor faults that offset foliation in the schists. Major cross folds are present in the north-western part of the area. Numerous smaller folds with axial planes trending parallel to the regional trend of the schists are restricted mainly to the higher-rank schists. Although the rocks are situated on the north side of the active Wairau Fault, and presumably have been involved in the structural adjustment along the major Alpine Fault of New Zealand’s South Island, it is difficult to assign a definite age to the syn-metamorphic deformation. A wide scatter of lineation and poles of foliation, joint, and fault planes and the relation of these to the schistosity and major structures suggest that much of the faulting in the region is post metamorphic, probably of Tertiary age and related to the major fault at Picton. (auth)