Notes on the Geology of Kapiti Island, Cook Strait, N.Z.
[Read before the Wellington Branch, October 9, 1947; received by the Editor, March 4, 1948; issued separately, September, 1949.]
Rocks previously reported as schist are exposed in a narrow linear zone on the east coast of Kapiti Island. Petrographic study shows that the rocks are not the products of regional metamorphism, but are phyllonites resulting from the intense cataclasis of sediments similar to those forming the bulk of the island. The zone of phyllonites is, therefore, mapped as a fault zone in the pre-Cretaceous rocks. The physiography of Kapiti suggests that it is part of a dome-like anticlinal fold developed on a late-Tertiary peneplain cut in the pre-Cretaceous rocks, and separated from the greater anticline of the Tararua-Range by a syncline; continuity between these folds and the Mount Stewart Dome and Pohangina Syncline, to the north-east, is indicated. The submarine topography suggests that a ridge at one time extended from Kapiti to the eastern Marl-borough Sounds, and that a continuous tectonic scarp joined the east coast of Kapiti and the west side of the Wairau Plain.
During a two-day visit by one of us (C. A. F.) to Kapiti Island, in January, 1942, the opportunity was taken to examine and map part of the south-east coast of the island in an endeavour to find the relationship between the “schist” reported by Ferrar (1928) and the indurated pre-Cretaceous sediments forming the rest of the island. The rocks collected have been studied by the other author (C. O. H.), and the results of this study form Part II. of this paper.
Thanks are due to Mr. A. S. Wilkinson, until 1943 the caretaker of the Kapiti Island bird sanctuary, for hospitality and transport facilities, and for valued information, and to Mr. N. H. Taylor for suggestions arising from his independent observations at Kapiti some years ago